Abstract:With the steady advancement of major national engineering projects， the construction scale of long deeply buried tunnels and deep rock mass projects has been expanding year by year. Engineering hazards frequently occur， including large surrounding rock deformation， rock bursts and collapses induced by high geostress， which severely threaten construction safety and long-term operational stability. The formation and evolution of geostress are jointly governed by deep earth dynamics， intrinsic rock mass properties and external environmental factors. Acquiring accurate geostress data is of great significance for the construction of deep rock mass projects. This paper firstly systematically sorts out five major dynamic formation mechanisms of geostress， and analyzes the control laws of geological structures， landforms， rock mechanical properties and other factors on the spatial distribution of geostress. On this basis， mainstream geostress measurement techniques， namely hydraulic fracturing， borehole wall deformation， borehole bottom stress relief， stress recovery and acoustic emission method are classified and elaborated. The measuring principles， operational procedures， applicable conditions， advantages and limitations are discussed. Furthermore， commonly adopted geostress calculation approaches are summarized from three dimensions： theoretical analysis， numerical simulation and intelligent algorithms. The fundamental principles and application characteristics of classical elastic mechanics algorithms， numerical simulation methods and intelligent algorithms are illustrated in detail， and the factors affecting the calculation accuracy of different methods are investigated. Finally， suggestions are put forward in terms of upgrading testing equipment， improving multi-field coupled geostress calculation models， and realizing deep integration between intelligent algorithms and traditional methods. The presented research can provide valuable references for engineering investigation， deep rock drilling， mining and related engineering practices.

Abstract:Horizontal directional drilling is a core technology for achieving green exploration， yet the development of its budget standard system lags significantly， restricting the high-quality development of the technology and the green transformation of the industry. Through literature review， comparative analysis， and system construction methods， this paper systematically analyzes the connotation， characteristics， and cost structure of horizontal directional drilling. It identifies prominent issues in current budget standards， such as insufficient depth coverage， failure to integrate the green exploration concept， and failure to distinguish the cost composition between fiscal and non-fiscal expenditure projects. Furthermore， it proposes formulation suggestions， including comprehensively collecting and sorting key data， multi-dimensionally adapting to technological iteration processes， systematically incorporating green exploration requirements， and categorically formulating budget standards for fiscal and non-fiscal expenditure projects. The research findings provide theoretical support and reference for improving the budget standard system for horizontal directional drilling， promoting the implementation of green exploration， and serving the new round of strategic action for prospecting breakthroughs.

Abstract:Efficient exploitation of natural gas hydrates constitutes the foundation and prerequisite for their commercial utilization. As one of the vital exploitation technologies， the chemical reagent injection method facilitates hydrate dissociation by altering hydrate phase equilibrium conditions and destroying cage structures. This paper reviews the research progress of hydrate exploitation including injected alcohols， salts and hot acid solutions， and analyzes the action mechanism of various injected chemical reagents， hydrate dissociation efficiency and combined exploitation processes. The results demonstrate that alcohol-based reagents achieve thermodynamic inhibition mainly by reducing water activity via hydrophilic hydroxyl groups， yet their application suffers from severe environmental pollution and large injection dosage. Salt reagents feature low costs and environmental friendliness， while exhibiting limited exploitation potential when used alone， and combination with depressurization or thermal stimulation can boost reservoir gas production efficiency by nearly 50%. Hot acid injection enhances gas production through the synergy of chemical dissolution and heat transfer， whereas relevant mechanism research remains incomplete. Marine argillaceous silty hydrate reservoirs are characterized by high fine particle and clay contents as well as low permeability， which brings about injection obstacles for the chemical reagent injection method. The compatibility between reagent type， concentration and reservoir conditions requires urgent investigation. This study can provide references for the efficient exploitation of natural gas hydrates via chemical reagent injection.

Abstract:Deep and ultra-deep fractured-vuggy loss channels are characterized by abrupt aperture variation， rough walls， local expansion and strong distal connectivity， which may cause premature entrance sealing， deep material loss or erosion-induced failure of the plugging zone. To clarify the governing mechanism for the transition of lost-circulation-control slurry from transportation to retention，this review examines particle-scale CFD-DEM and related simulations published mainly during the past decade， with emphasis on computational domains， mesh size， time steps， boundary conditions， contact laws， fluid constitutive models and validation， and quantitative results are adopted for synergistic material design analysis.The results show that in a specific rough-fracture model with a ratio of particle diameter and fracture width （d/W）=0.4， a wall-friction coefficient of 0.5 and an inlet velocity of 0.1 m/s， an 8% particle volume fraction did not seal within 3 s， whereas 10% and 20% sealed at 2.6 and 2.2 s， respectively. A separate three-dimensional fracture study identified a model-specific favorable combination of particle size of 0.50~0.67 W， concentration of 8%， carrier-fluid viscosity of 50 mPa·s and wall-friction coefficient of 0.7~0.9. In a shape-memory-particle simulation for 2~5 mm fractures， increasing the inlet-outlet dimensions from 3 mm×2 mm to 5 mm×4 mm， increased sealing time from 0.11s to 0.25 s and loss ratio from 4.6% to 12.3%. A design combining absolute bridging dosage with gap-filling dense packing increased pressure-bearing capacity by 100%~229%， while reduced cumulative loss by 31%~38% and material consumption by 28%~76% in three comparative cases. These thresholds are conditional on channel geometry， particle shape and boundary settings and should not be treated as universal formulations. Based on this， a collaborative design workflow integrating channel parameterization， geometric gradation， carrier-fluid rheology， high-temperature functional retention and multiscale validation is therefore proposed， which provides support for the lost-circulation-control material transportation from empirical compounding toward computable and verifiable design.

Abstract:To clarify the key issues and development directions of borehole trajectory control for small-diameter directional drilling in underground coal mines， this paper systematically reviews research progress in borehole deviation mechanisms， trajectory-control tools， measurement while drilling， near-bit sensing， trajectory prediction， and intelligent control， with emphasis on the requirements of long-distance near-horizontal boreholes for trajectory accuracy， borehole stability， and drilling efficiency. The analysis shows that the alternating distribution of coal seams， partings， broken soft coal， hard roof and floor rocks， and structural fracture zones causes continuous variations in bit loading， borehole stability， weight-on-bit transfer， and cuttings transport conditions. These variations may result in deviation along bedding planes， cross-layer deviation at soft-hard interfaces， reduced efficiency of borehole deviation correction in hard-rock intervals， and cumulative borehole-trajectory errors in long-distance drilling. Small-diameter conditions further constrain the coordinated integration of positive displacement motors， stabilizers， measurement subs， power-supply and communication modules， and cuttings-removal passages. At present， single-bend positive displacement motors remain the basic tools for deflecting and borehole deviation correction. Compound directional drilling， rotary steerable drilling， PDC bits， multi-power drilling assemblies， and multi-parameter measurement-while-drilling systems provide complementary functions in angle holding， rock breaking， flushing and cuttings removal， and information feedback. However， their adaptability to small-diameter boreholes， operational reliability in complex coal-measure strata， and field validation of closed-loop control remain insufficient. Future research should strengthen the coupling between borehole deviation mechanisms and engineering data， develop miniaturized near-bit sensing and reliable data-transmission technologies， promote the integration of mechanism-based and data-driven models， and convert prediction results into executable parameters， including tool face angle， weight on bit， rotary speed， pump discharge， and switching between sliding drilling and rotary drilling， thereby establishing a closed-loop control system integrating sensing， prediction， decision-making， execution， and verification.

Abstract:Diamond drilling is an important method of drilling and used widely in various countries. Diamond drill bit is a main tool for fragmentating rock in this method. In some countries in drilling of medium-strength and above-strength rocks impregnated bits are used usually. In designing of the impregnated drill bits many rock character factors are considered and good results have been obtained. That should attract attention of Chinese researchers. In diamond drilling a suggestion of using critical drilling parameters has been put forward. The critical drilling parameters has important significance for normal drilling， safe production and preventing accidents. Combining the good drill bit with the good drilling parameters can increase drilling results substantially and make our more contributions to the performance economic construction of China.

Abstract:The crown structure of an impregnated diamond bit is a critical factor affecting its rock-breaking efficiency and drilling performance. The ridge arrangement of a ridged impregnated diamond bit directly determines the cooling and cleaning performance of drilling fluid acting on the bit crown at the bottom hole. To investigate how ridge arrangement affects the flow characteristics of fluid over the bit surface， three ridge layouts （forward， reverse and symmetric） are designed for bit crowns of ridged impregnated diamond bits with an outer diameter of 78 mm and an inner diameter of 48 mm. Using clean water as the working medium， ANSYS Fluent is adopted to conduct hydrodynamic simulations of fluid flow on the bit surface. Under a bit rotational speed of 62.83 rad/s， the flow characteristics and velocity distribution of surface fluid with different ridge layouts are compared， and the influence of structural parameters on fluid flow behavior is clarified. The simulation results show that the maximum fluid velocity for all three layouts occurs near the water ports， ranging from 7.92 to 9.15 m/s. High-velocity zones between ridges concentrate at the front edge of ridges facing the rotation direction. The forward layout imposes the weakest disturbance on inter-ridge fluid velocity. The flow velocity at ridge fronts reaches 5.60 m/s， approximately 17.89% and 2.04% higher than those of the reverse and symmetric layouts， respectively， and the high-velocity zone can cover the high-temperature regions at the front of the three ridges. The inter-ridge velocity of the forward layout reaches 3.20 m/s， which is about 102.50% and 247.80% higher than the reverse and symmetric layouts， respectively. Meanwhile， the ridges in the forward layout exert the least influence on fluid streamlines. Comprehensive analysis demonstrates that the forward ridge arrangement is optimal for preserving surface flow velocity， improving ridge cooling conditions and enhancing the removal of cuttings between ridges and at the bottom hole.

Abstract:The complex operating conditions encountered in deep， ultra-deep， and high-temperature geothermal wells impose stringent requirements on the high-temperature adaptability， output stability， and service reliability of downhole motors. The test in the ground simulation environment becomes the key link before the drilling tool enters the well. However， facilities capable of dynamically testing downhole-motor at temperatures of up to 300 ℃ under high-pressure conditions remain unavailable， constituting a key technical challenge， which must be addressed in deep-earth drilling projects. In this study， surveys and comparative analysis are firstly made including the technical characteristics and major limitations of representative downhole-motor testing systems developed in China and abroad. To meet the requirements of scientific drilling in 10000 m-class ultra-deep wells， a preliminary testing scheme for high-temperature downhole-motor is then proposed. A closed-loop circulation system for high-temperature， high-pressure drilling fluid is established using multiple high-temperature screw pumps connected in series， whole-system thermal insulation， and centrally cooled distributed rotary seals. Drive-load regenerative energy feedback and condition monitoring are incorporated to reduce power consumption and support extended-duration testing. Simulated loading and actual rock-drilling modules are integrated to evaluate the operating characteristics of downhole-motor as well as their adaptability to drilling and coring processes. The proposed scheme provides a technical basis for the subsequent development of a high-temperature downhole-motor test platform.

Abstract:To address the low bulk stock-removal efficiency and severe grinding-wheel wear encountered during the mechanical grinding and profiling of superhard composites such as polycrystalline diamond （PCD） hardbanding， an experimental study was conducted into the process applicability and efficiency enhancement of electrical discharge machining （EDM） for PCD hardbanding profiling. Unlike hybrid processes in which electrical discharge and mechanical actions occur simultaneously within the same machining zone， and electrical discharge grinding using a rotating wheel electrode， the proposed method arranges electrical discharge machining and mechanical grinding as sequential， independent operations and allocates the machining allowance across three stages： EDM roughing， profile grinding with a 60-grit wheel， and finish grinding with a 400-grit wheel. The investigated PCD hardbanding consisted of thermally stable polycrystalline diamond （TSP） blocks embedded in a metal matrix. Firstly， the EDM responses of the metal-matrix material and TSP material were characterized separately. The EDM parameters for machining the composite surface were then optimized. Finally， the hardbanding was profiled by EDM and subsequently finished by mechanical grinding， and the combined process was comparatively evaluated against pure mechanical grinding and pure EDM alone. The results showed that pure mechanical grinding produced a surface roughness of 2.63 μm， but its mass removal rate was only 0.20625 g/h， resulting in limited machining efficiency. EDM achieved a mass removal rate of up to 1.23053 g/h， demonstrating substantially higher stock-removal efficiency. Although the EDM-processed surface exhibited a roughness of 16.62 μm and could not directly satisfy the surface-quality requirement， subsequent mechanical grinding with a small finishing allowance increased the overall mass removal efficiency by 160.2% compared with pure mechanical grinding， while reducing the surface roughness to 2.92 μm， a level close to that achieved by pure mechanical grinding. These results demonstrate that， after appropriate parameter optimization， EDM can be effectively applied to the high-efficiency profiling of superhard composites used in PCD hardbanding. The proposed process provides a technical reference for machining PCD hardbanding on drillpipe tool joints used in deep-well drilling.

Abstract:Rate of penetration （ROP） is a critical indicator for evaluating drilling efficiency and downhole drilling conditions. Accurate ROP prediction is essential for improving intelligent drilling. However， the coupled effects of formation properties， drilling parameters， and operational variations make it challenging for conventional models to simultaneously capture long-term trends and short-term fluctuations， and online prediction is prone to future information leakage. To address this issue， an online EWMA-LightGBM-Huber model based on trend-residual decomposition is proposed for ROP prediction. First， a strict one-sided processing strategy is adopted to perform outlier handling and noise reduction on drilling data， thereby avoiding future information leakage. The exponentially weighted moving average （EWMA） method is then employed to extract the local trend component of ROP. Subsequently， drilling parameters and historical ROP features are integrated， and LightGBM is used to learn the residual component between the actual ROP and the extracted trend. The Huber loss function is further introduced to improve model robustness against abnormal fluctuations. Finally， a sliding-window updating strategy is incorporated to achieve online model updating while drilling and continuous depth-wise prediction. The results demonstrate that the proposed model achieves an R² of 0.9333， with the RMSE reduced by 8.72% and the MAE reduced by 11.92% compared with the best-performing benchmark model RF， exhibiting superior prediction accuracy and stability. Ablation experiments verify the effectiveness of trend extraction， residual learning， and robust optimization modules. Furthermore， sliding-window analysis determines appropriate parameters for online updating. This study provides an effective data-driven framework for real-time ROP prediction under complex drilling conditions.

Abstract:Aiming at the challenges in borehole trajectory control under dense well patterns， including constraints from multiple adjacent wells， sensitivity to the input order of obstacles， and stable control of continuous actions， this paper proposes an intelligent control method for multi-obstacle well constrained borehole trajectory named DeepSets-TD3. The method recursively calculates the borehole trajectory using the minimum curvature method， and takes the increments of inclination and azimuth as continuous control actions. The basic state consists of the relative displacement of the target， inclination angle， as well as the sine and cosine values of azimuth angle. Each element in the set is constructed by the surface clear distance of obstacle wells and the sine and cosine values of relative azimuth. A permutation-invariant representation is formed via a shared encoder network and mean-max symmetric pooling. In the test with four fixed obstacles， the DeepSets-TD3 achieves an average target error of 7.52 m and zero physical collision rate. In the random four-obstacle test， the average target error is 11.2 m， the physical collision rate is 1.2%， the near-miss buffer rate is 1.9%， and the compliance rate of dogleg severity reaches 99.6%. All four indicators outperform the conventional TD3. The results demonstrate that the set representation can mitigate policy degradation caused by changes in the arrangement of obstacle wells， and improve the accuracy， safety and generalization capacity of trajectory control under complex constraints of adjacent wells.

Abstract:Conventional unresolved CFD-DEM methods are limited by the constraint between grid size and particle diameter， making it difficult to efficiently simulate large-scale geomaterials with a wide particle size distribution. To address this issue， this paper presents the secondary development of a mixed unresolved CFD-DEM coupling framework. In this method， the ratio of fluid grid size to particle diameter serves as an automatic criterion. For fine particles with a ratio greater than 3， a sampling-point method is employed for volume fraction mapping and particle-fluid momentum exchange； whereas for coarse particles with a ratio less than 3， a Gaussian kernel function is introduced for smoothed volume fraction mapping， and the particle-induced fluid momentum source term is distributed over an extended region. Furthermore， to correct the mapping error caused by truncation of the kernel function''s extended domain at fluid boundaries when particles approach walls， a normalization correction based on grid-volume weighting is adopted to ensure conservation near boundaries. Based on the developed program， three verification tests， namely， volume fraction conservation， single-particle settling velocity， and Ergun pressure drop in a spherical particle column are designed to evaluate the reliability of the mixed unresolved CFD-DEM coupling framework in applications involving wide particle size distributions. The results demonstrate that the proposed method can balance computational efficiency and coupling stability in simulations of polydisperse particle systems， providing a feasible numerical approach for problems such as grouting permeation in soil-rock mixtures， fine particle migration， and seepage through particle columns.

Abstract:This paper introduces the research objectives， applicable environment， structure， composition， working parameter calculation， functional tests and drilling experiments of a lunar sampling drill. This drill is expected to provide astronauts on the moon with a lunar exploration drill scheme and prototype that combines manual and automatic operations， enabling multi-site， multi-hole， multi-depth， multi-cycle， multi-variety and high-quality lunar sampling， for relevant departments to select and reference. The development of the "Wigen" sampling drill covers the entire set of supporting devices including special sampling drilling tools， drill rig fixation， and manual control systems， adopting the lifting-type percussive-rotary rock-breaking drilling method. After further improvement， it is also expected to realize the drilling of blast holes， geophysical prospecting holes and anchor holes on the moon， to support tasks such as mineral exploitation and scientific research base construction. The "Wigen" sampling drill reserves matching installation positions， providing preliminary technical reserves for the development of remote-controlled lunar automatic sampling drills or remote-controlled lunar multi-functional automatic sampling drills. The scheme and prototype of this drill can also serve as a reference for the development of Mars sampling drills.

Abstract:Aiming at the problems of high labor intensity， high safety risks and insufficient process coordination in field operations of vertical shaft drills using trip-out coring technology， this paper proposes an automatic upgrade scheme and human-machine collaborative operation method. Adopting the technical route of "main engine upgrading and incremental supporting matching"， the scheme replaces mechanical vertical shaft drills with electric-drive vertical shaft drills， realizing stepless speed regulation， real-time parameter monitoring and remote control through electric transmission. On this basis， a collaborative operation system covering derrick and wellhead is formed by integrating self-elevating drilling derrick， remote-control elevator， platform manipulator， integrated wellhead pollution reduction device and pipe spinner. Finite element simulation is conducted on the derrick structure to verify the structural safety and reliability under the lifting state. In addition， a collaborative tripping operation process is designed with clear time sequence connection and trigger conditions for each procedure， and a PLC bus-based safety interlock logic is established. Theoretical analysis shows that the scheme reduces the team staffing from 3~4 workers to 2 and realizes unmanned derrick operation. Meanwhile， it reduces the wellhead pollution area and shortens the tripping time of 6 m drill stands from 100 s to about 70 s， improving the tripping efficiency by approximately 42.9%. This study provides a feasible technical path for the automatic upgrading of vertical shaft drills adapted to trip-out coring technology， and has positive significance for promoting staff reduction， efficiency improvement and green exploration in the geological drilling industry.

Abstract:In response to the risks such as traction failure， wire rope disorder and breakage faced by the 13000 m wireline core drilling winch during ultra-deep well operations， an electrical control system based on the Siemens S7-1500 PLC and Profinet fieldbus was designed. The system adopts a modular design， integrating AC variable frequency drive， multi-source information acquisition， and dynamic braking， and it features three operation modes， namely， local control， wireless remote control， and centralized control in the remote driller''s cabin. For key control strategies， the dual traction motors implement load balancing through master-slave control with "speed closed-loop synchronization + load distribution". A tension closed-loop PID control is constructed using pressure sensors of the slack compensator， enabling the line speed of the cable storage drum to automatically follow the traction speed and achieve constant-tension cable winding and unwinding. The cable arrangement mechanism employs encoder calculation and angle sensor measurement as redundant methods to realize precise position tracking and automatic direction reversal. In terms of hardware， a VFD room integrating the PLC control cabinet and frequency conversion cabinet was designed， equipped with industrial wireless remote control and an upper computer configuration interface. This system can effectively improve the control accuracy， operational flexibility， and operational safety of the winch， providing technical support for the research and development of ultra-deep wireline core drilling equipment. The control system scheme can serve as a technical foundation for enhancing the automation level and ensuring safe operations of wireline core drilling winches for the ultra-deep hole.

Abstract:The centrifugal-pump-type riser-less mud lifting pump is adopted in offshore drilling， lifting mud by motor-driven impeller rotation. During long term operation， abundant cuttings carried in drilling fluid cause severe impeller wear， which seriously impairs normal service of the mud lifting pump. Therefore， it is necessary to adopt wear-resistant treatment for impellers to improve their wear and corrosion resistance. In this study， impeller substrate materials were optimized， surface wear-resistant treatment processes were investigated， and wear-resistance tests were carried out. The test results show that 2205 duplex stainless steel possesses favorable comprehensive properties and is suitable for riser-less mud lifting service conditions. Tungsten carbide supersonic spraying achieves the most significant improvement in impeller wear-resistance. Duplex stainless steel is recommended as the impeller substrate material for mud lifting pumps， combined with tungsten carbide supersonic surface spraying， so as to extend the service life of mud lifting pumps.

Abstract:The traditional power transmission of drilling pumps mostly adopts crank-linkage mechanisms or hydraulic transmission methods， which have problems such as heavy structure， significant pressure and flow pulsation， insufficient working volume for construction operations， and low efficiency. Based on the technical requirements for drilling pumps with large flow rates and high efficiency in the development of deep and ultra-deep well as well as unconventional oil and gas resources， this article discusses a new type of electric cylinder-driven system for drilling pumps. This system consists of four major modules： power， transmission， execution， and auxiliary. It forms an integrated power transmission system of "power+control+auxiliary" that works collaboratively， transforming the driving method of drilling pumps from the traditional crank-linkage mechanism to electric cylinder drive. The proposal of this system can improve the transmission efficiency of drilling pumps， reduce output pressure pulsation， save equipment maintenance costs， and precisely adapt to the working characteristics of high-load， large-flow， and continuous operations of drilling pumps at oilfield operation sites. It provides a new technical path for the development of drilling pumps towards efficiency， intelligence， and environmental friendliness.

Abstract:Aiming at the prominent problems encountered in borehole construction for geological exploration on the Qinghai Plateau， including large volumes of waste and residual drilling fluid， high treatment costs， fragile plateau ecological environment and stringent environmental protection requirements， as well as the poor adaptability of existing treatment technologies and equipment to field operation demands， this paper carries out research and development of a green exploration drilling fluid treatment device suitable for the Qinghai Plateau environment. Conventional physical and chemical treatment technologies for waste drilling fluid are sorted out， the practical requirements for waste drilling fluid treatment in plateau exploration construction through field investigations are identified， the structural design， feasibility study and manufacturing of the treatment device are completed， field application tests are conducted and various environmental indicators of treated products are tested and analyzed. The test results show that the self-developed waste drilling fluid treatment device can effectively realize the reduction and harmless treatment of waste drilling fluid generated from the exploration boreholes on the Qinghai Plateau. It can reduce the comprehensive cost of waste drilling fluid treatment while complying with the local environmental protection standards， and fits the operation characteristics of scattered field construction on the plateau. This research can provide equipment and technical support for green exploration construction on the Qinghai Plateau.

Abstract:To address the problems of rapid diamond bit wear， frequent premature failure， and excessive bit replacements during wire-line coring drilling in granite-hosted uranium deposits， a comprehensive analysis was conducted using construction data from 12 boreholes in the Zhuguangnan ore concentration area together with laboratory measurements of rock drillability， indentation hardness， compressive strength， abrasion resistance， and chemical composition. The analysis covered bit wear morphology， lithology of intersected intervals， drilling parameters， flushing fluid conditions， and on-site operational records. A set of technical measures was developed， including lithology-adapted bit selection， controlled windows of weight-on-bit， rotary speed， and pump rate， cooling and chip-carrying capacity of the flushing fluid enhancement， initial run-in treatment for new bits， and low-disturbance drilling through fractured zones. Field application results show that the average rate of penetration increased from 2.02 m/h to 2.61 m/h， the average footage per bit rose from 91.2 m to 109.2 m， and the abnormal bit failure rate decreased from 32.7% to 14.3%.

Abstract:To address the wellbore instability caused by nano-micro-scale pores and fractures in deep shale formations， a nano styrene-acrylate emulsion plugging agent was synthesized via semi-continuous seed emulsion polymerization using styrene， butyl acrylate， acrylic acid， acrylamide， and 2-acrylamido-2-methylpropanesulfonic acid as monomers， and its structural characterization and performance evaluation were carried out. The results show that the emulsion has a median particle size （D₅₀） of 174.5 nm with a unimodal distribution； the particles are spherical or nearly spherical and stably dispersed， and the solid content is higher than 80%. After hot-rolling aging at 180 ℃ for 16 h， the high-temperature and high-pressure （HTHP） fluid loss of the drilling fluid decreases with increasing emulsion dosage， while the API fluid loss reaches its minimum at a dosage of 2.5%. Considering both fluid loss control performance and economic efficiency， the optimal dosage is determined to be 2.5%， under which a thinner and denser filter cake is formed and the reduction rate of clear-water fluid loss of the filter cake reaches 41.7%. The emulsion exhibits favorable compatibility with conventional drilling fluid additives. After aging at 150 ℃， compared with the blank system， the HTHP fluid loss of the nano-emulsion-containing system decreases from 15.3 mL to 13.2 mL， and the 10 μm sand-disk fluid loss decreases from 7.2 mL to 5.6 mL， indicating good plugging performance for micron-sized fractures， improved filter-cake quality， and beneficial effects on wellbore stability.

Abstract:As the environmental regulations become increasingly stringent， drawbacks such as the dark appearance and inadequate environmental performance of conventional materials have emerged as the key issues restricting the application of anti-collapse agents in drilling fluids. To address this challenge， as an environmentally friendly white anti-collapse agent， GHF was developed by synthesizing low-molecular-weight sodium polyacrylate and subsequently subjecting it to a kneading reaction with materials such as viscous resin. Research indicates that the addition of 0.5% GHF to commonly used drilling fluids， including LBM， environmentally friendly dual-polymer， and environmentally friendly film-forming， exerts no adverse effect on the rheological properties of the drilling fluids， while also providing a certain degree of filtration loss reduction. At a concentration of 1%， GHF exhibits favorable plugging and filtration-control performance， with a filtration loss of only 7 mL within 30 min and a penetration depth of 1.5 cm into the formation， demonstrating its excellent plugging capability for low-permeability formations. Furthermore， compared with clean water， the aqueous solution containing 1% GHF achieves a shale swelling reduction rate of 55.6%， indicating that this environmentally friendly anti-collapse agent can effectively prevent complex downhole incidents such as borehole wall collapse.

Abstract:In thick loose overburden covered areas such as Fuyang and Bozhou in northern Anhui， the incidence of downhole accidents including borehole shrinkage and collapse during drilling exceeds 80%. By analyzing the characteristics of loose layers， this paper reveals the chain instability mechanism of borehole walls dominated by "hydration expansion-particle migration-mud cake failure". The key control indicators are proposed， including the filtration loss of flushing fluid ≤5 mL/30 min and mud cake cohesion>8 kPa， which can ensure the safety of long open-hole drilling for more than three months. A composite flushing fluid system consisting of KPAM， NH₄-HPAN， PAC-LV and ultrafine calcium carbonate is developed， and a technical process featuring "layered targeted treatment+plugging while-drilling+short tripping" is formed. The verification of four test boreholes shows that the borehole wall stability coefficient increases from 0.51 to 0.89， the accident handling time is reduced by 100%， the mechanical drilling rate is increased by 32.8%， and the monthly drilling efficiency of a single rig exceeds 800 m. The research results can provide technical support for drilling engineering in similar thick loose overburden layers.

Abstract:The existing drilling test rigs are constrained by limited space， poor stability， and low automation， making them inadequate for testing downhole tools in high-build-rate directional drilling. To address these challenges， a novel test platform for high-build-rate directional drilling was developed. The platform adopts a modular structure consisting of rig zone， rock sample zone， simulated wellbore， tool fixing zone， circulation system， and data management system. Stability against overturning is enhanced via triangular brackets on both sides， while structural load-bearing and rapid positioning are achieved using symmetrical channel-steel guide rails. The support for the guide pipe utilizes a triangular truss structure， which works in conjunction with a bottom fixing plate to ensure coaxiality during operation. The power head mast of the drilling rig can tilt from 0 to 90°， enabling the dynamic adjustment of drilling parameters such as feed pressure， torque， and rotational speed. Moreover， the simulated wellbore is equipped with pressure and torque sensors to collect key real-time parameters at the bit， including weight on bit （WOB）， torque， and vibration. Based on this platform， real-drilling and mechanical testing experiments were conducted on flexible drill strings， alongside directional side-tracking using flexible downhole power tools. The results indicate that the test platform features a rational structural design and operates smoothly. It can effectively simulate actual drilling conditions for high-build-rate directional tools， thereby providing a reliable experimental means for testing downhole tools and researching drilling technologies in high-build-rate directional wells.

Abstract:To address the problems of existing plugging evaluation instruments， such as cumbersome manual operation， poor data stability， insufficient safety， and low field plugging success rate， a visualized fracture evaluation instrument based on a digital twin system was developed， along with a wide-temperature range filtration-type composite structure plugging fluid. The instrument integrates a 3D visualization control interface， a physical perception tracking system， and an experimental management platform. It achieves a data acquisition accuracy of ±0.5%FS， a transmission rate of 1~5 Mbps， a system stability of >99.5%， and a maximum pressure capacity of 5 MPa. Capable of simulating 1~5 mm fractures， it enables remote operation and visual observation of the plugging process， thereby significantly improving experimental safety. Based on this instrument， the wide-temperature range filtration-type composite structure plugging fluid was developed； by optimizing the dosages of the main agent and suspending agent， plugging formulations adaptable to different fracture widths were formulated. Experimental results show that the plugging fluid can effectively seal 1~3 mm fractures， with a consolidated strength of ≥8 MPa and a drillability grade of 2~3. Field applications in 24 wells demonstrate a one-time plugging success rate of 87.5%， with normal circulation restored and no leakage after operations. The results indicate that the instrument and plugging fluid significantly enhance the safety and efficiency of plugging evaluation， providing an intelligent solution for the effective treatment of fractured loss zones.

Abstract:To address the problems in large-diameter pile foundation construction， such as experience-dependent parameter control， scattered monitoring data， and outliers easily caused by electromagnetic interference， which further lead to delayed early warning and lack of real-time quantitative characterization of construction status， an integrated system is proposed. This system combines condition monitoring， risk warning， fuzzy PID-based parameter adaptive regulation， and limited closed-loop control for over-limit emergency shutdown. Constructed upon a layered Internet of Things （IoT） architecture， the system integrates sensing units for rig attitude， power systems， drilling parameters， environmental conditions， mud level， and mud density. It is equipped with a non-contact hole depth monitoring unit based on infrared ranging and infrared mutual beam detection， along with an intelligent monitoring platform. A two-level data fusion method， a graded early warning model based on a comprehensive risk index R （with weights determined by the analytic hierarchy process）， and an adaptive optimization strategy for drilling parameters are established for pile foundation construction scenarios. Field test results indicate that， compared with manual sounding rope measurements， the average error of hole depth monitoring is ±6.2 mm； the response time for mud level alarms is less than 2.1 s； the early warning accuracy reaches 92.3% when validated against actual risk events； and the average hole completion time per pile is reduced by approximately 18% compared to manual empirical operation. The research results can provide technical support for intelligent decision-making， refined operation， and safe construction of large-diameter pile foundations under complex geological conditions.

Abstract:In response to the special conditions in the Qiangtang Basin， Xizang， such as high altitude， severe cold and oxygen deficiency， prone to loss and diameter reduction in the interbedded potash-limestone formations， and ecologically sensitive plateau environments， a full-process quality control system of "pre-drilling planning， strict in-process control， verification and archiving， closed-loop improvement" was established based on the 901.50 m medium-deep core drilling project of QS6 drilling hole. The control indicators and technical measures were established from seven dimensions， including core recovery， borehole deviation， depth accuracy， simple hydrological observation， raw data， hole sealing operations， and quality supervision. The engineering practice shows that the core recovery rate of this drilling hole reached 98.44%， the maximum hole inclination was 2.0°， the depth calibration error was ≤2 cm， and no in-hole accidents or mechanical failures happened， in addition， the raw data were standardized， the drilling hole sealing met the quality requirements and all indicators surpassed the design specifications and the requirements of the "Geological Core Drilling Code". The resulting quality control model for medium-deep drilling in the plateau can effectively ensure the reliability of drilling results under complex strata conditions， providing technical support for mineral survey and evaluation drilling in the Qinghai-Xizang Plateau.

Abstract:To address the challenges of difficult transportation， stringent site requirements， high construction costs， and low hard-rock drilling efficiency when using conventional large drilling rigs for deep-hole drilling in high-altitude and complex terrains. Through systematic technical research and innovation， a comprehensive technical system for deep-hole drilling with portable rigs has been established. In site construction， an innovative site layout approach was adopted， incorporating a "rubble concrete base platform + double anchor rod anchoring" installation method， which effectively resolves the constraints of rugged terrain and the requirement for equipment stability. In equipment configuration， the selection of drill pipes， bits， and other auxiliary components was optimized， and the gripper support structure was improved to enhance load capacity. In drilling techniques， a four-stage borehole structure was designed， and process improvements were implemented to increase hard-rock drilling efficiency. The "power head nodding effect" was identified as a factor influencing drill pipe service life， and the "JFC drilling fluid analysis method" was proposed for real-time drilling fluid performance optimization. Preventive measures for downhole accidents and an innovative "spring-type" stuck pipe release technique were introduced. Additionally， a multi-dimensional green exploration system was established to meet the environmental requirements of no road construction and minimal disturbance within the drilling area. Field application results demonstrate that all borehole indicators meet the specifications， achieving one of the deepest boreholes drilling with portable rigs in recent years. This technical system provides a reliable reference for deep-hole drilling projects in similar high-altitude and complex terrains.

Abstract:Aiming at the long-term technical bottleneck of difficult construction of small-diameter core drilling for solid mineral resources in kilometer-scale loose strata in China， this study takes the YZK01 borehole in a mining area of Qinghai Province as the engineering example. Through industry-university-research collaborative study， a complete set of small-diameter wireline coring drilling construction technology system is established. The borehole reaches a final depth of 1120 m， and the entire hole section consists of weakly cemented mud-sand strata with continuous water and sand bursting phenomena. An innovative precise pressure-controlled drilling fluid technology of "drilling fluid recharge + stepwise weighting" is proposed. Through differentiated layered design and dynamic regulation， the control accuracy of drilling fluid density is improved to 0.02 g/cm³， and the drilling fluid colloidal stability rate is increased from 65% to more than 98%. A self-developed negative pressure sand cleaning drilling tool assembly is adopted， which forms instantaneous negative pressure through a one-way valve during fishing operations to effectively remove fine-grained rock powder （less than 0.75 mm） at the bottom hole， with the cleaning efficiency more than three times higher than that of the traditional dry grabbing deslagging method. Meanwhile， a refined drilling parameter system characterized by "low speed， low pressure and small footage" is established， in which the weight on bit， rotational speed and run footage are controlled at approximately 50%， 60% and 30% of the conventional values， respectively. Field application results show that the average daily drilling footage is increased from the initial 3.2 m to 24.25 m， increased by about 658%. All key indicators including borehole verticality and core recovery rate meet the specification requirements. The novelty search report verifies that the research results fill the domestic technical gap of small-diameter drilling in kilometer-scale weakly cemented sand-bursting strata， and possess important engineering application value for deep mineral exploration in complex overburden areas of western China.

Abstract:Aiming at prominent drilling challenges in the Z20 Mining Area of the Rossing Deposit， Namibia， including strong lithologic heterogeneity， interbedded soft and hard rock layers， well-developed primary bedding， brittle disintegration of hard rock masses and densely distributed joints and fractures， this study intends to improve core recovery quality and enhance the reliability of geological logging data. Two boreholes in the mining area， borehole R181 in fractured strata and borehole R239 in intact strata， are selected as research objects. A systematic comparative analysis is carried out between the conventional double-tube coring technology and the split-tube coring technology， based on three key evaluation indicators： core recovery rate （RCR）， rock quality designation （RQD） and core fragmentation index （CFI）， combining with field engineering application effects. The test results demonstrate that the split-tube coring technology achieves remarkably superior performance in all three core indicators compared with the conventional double-tube technology， especially in the fractured strata. This technology can effectively mitigate secondary core breakage and core loss， prevent distortion in rock mass integrity evaluation， and completely preserve the primary structural characteristics of strata. Large-scale field application verification proves that the split-tube drilling technology delivers excellent comprehensive construction performance. A total drilling footage of 10527.37 m was completed， with an average core recovery rate of 95.73% across the whole mining area， and all finished boreholes were rated excellent in construction quality. The technical conclusions obtained in this research can provide reliable technical references for coring construction in the Rossing Z20 Mining Area and similar fractured complex strata at home and abroad， and the split-tube coring technology has broad prospects for popularization and application.

Abstract:To address the problems of tight schedule and frequent accidents in deep-hole core drilling in the Chating copper polymetallic mining area， the mechanisms of downhole accidents such as out-of-tolerance borehole deviation， casing fall-off， drill pipe fracture， and bit burning were analyzed in combination with the formation conditions and engineering practice of the mining area. A total of 62 boreholes were designed， with depths of 1000~2000 m， a total drilling footage of 96240 m， and an exploration spacing of 50 m. Three-spud and four-spud borehole structures were adopted according to hole depth； impregnated diamond bits and bentonite/KCl polymer-sulfonate staged drilling fluid systems were used； and drilling parameters were optimized. The results show that spudding-in before foundation solidification， improper casing placement， and human operational errors were the main causes of accidents. After the application of treatment techniques such as directional deviation correction with a positive displacement motor， artificial bottom hole with a cement plug， hole reaming， casing isolation of chloritic rock， reverse-thread drill pipe fishing， milling and jointing， and wire rope fishing without an inner tube， the drift angle of borehole ZK4503 decreased from 4.82° at 700 m to 0.4° at 1000 m， and drilling in borehole ZK4714 was resumed after 46 days of treatment for multiple downhole accidents. Spudding-in quality directly determines the effectiveness of deep-hole drilling， and high-quality spudding-in can reduce non-drilling time by 15%~30%. This study provides an engineering reference for deep-hole core drilling in this mining area and mining areas with similar conditions.

Abstract:The working area of Gansu Yema Copper Polymetallic Ore Exploration Project is located in uninhabited gobi desert area with harsh construction conditions. Affected by mineral genesis and geological structures， the strata in this area is featured by steep occurrence， frequent faults， and is prone to fragmentation， collapse and leakage. In addition， some strata show mud-making when encountering water. During the construction of inclined boreholes， pipe sticking and hole abandonment often occur， which caused economic losses and seriously affected the project schedule. Combined with drilling difficulties of the project， technical measures are adopted including tracked drilling rigs， low-solid-phase drilling fluid， and optimized borehole structure， providing experience for drilling engineering in similar mining areas.

Abstract:The Taojiang area on the eastern side of the Xuefeng orogenic belt has been subjected to multi-stage tectonic superposition， resulting in fractured strata， interbedded soft and hard rocks， and well-developed fractures. Core drilling in this area faces prominent challenges， including borehole wall instability， severe drilling fluid loss， and difficult core recovery， necessitating the establishment of a systematic drilling technology system tailored to this region. Taking three typical boreholes （ZK0001， ZK1901， and ZK2402） in the study area as engineering cases， the lithological characteristics of the drilled formations and complex structural conditions were systematically analyzed. To address various downhole complexities， an integrated suite of techniques was applied， including serialized bit optimization， dynamic optimization of the three-stage borehole structure， improvement of coring tools for fractured formations， and adjustment of drilling parameters. Furthermore， a graded lost circulation control system based on leakage rate classification was established， featuring "loss prevention while drilling， bridging plugging， and composite gel plugging." Engineering practice demonstrates that： After optimizing impregnated diamond bits， the effective footage per bit in gravel-bearing sandstone intervals increased to 80~150 m； using side-jet bits combined with low weight-on-bit and low rotary speed drilling parameters， the core recovery rate in fractured manganese-bearing ore layers consistently exceeded 95% and locally reached 100%； the plugging system efficiently handled various levels of lost circulation with leakage rates ranging from 3 to 11 m3/h. In borehole ZK2402， weighted drilling fluid was employed for managed-pressure drilling in the confined water-influx zone， and the casing was permanently retained after completion， thereby achieving "one hole for multiple purposes" and transforming the exploration borehole into a rural water supply facility. This study establishes a key technology system for efficient and safe core drilling adaptable to the complex strata on the eastern side of the Xuefeng orogenic belt， providing a technical reference for mineral exploration drilling projects in similar complex intracontinental orogenic structural zones.

Abstract:The Hongliugou Iron Ore Mine in Aksai， Gansu Province is located in a high-altitude region with extremely complex stratum conditions and generally poor rock mass integrity. Widely developed mudstone strata in the mining area are prone to hydration and expansion when encountering water， which easily induces complex downhole accidents including borehole shrinkage， stratum collapse and drilling tool sticking and buried. These problems result in high drilling difficulty， low drilling efficiency and delayed construction period. Centering on the core goal of safe and efficient wireline core drilling in complex strata， this paper systematically researches and constructs a comprehensive technical system for drilling construction. A series of integrated technical measures are adopted， including targeted optimization of borehole structure design to adapt to the variation law of complex strata， scientific dynamic adjustment of drilling parameters to match the characteristics of different rock layers， development and preparation of zonal flushing fluid adapted to the local lithology to stabilize the borehole wall， and optimization of drilling assembly to improve drilling adaptability. Field engineering practice verifies that the constructed comprehensive drilling technical scheme has good applicability and effectiveness. It effectively solves the technical difficulties of drilling in complex strata of the mining area， significantly improves borehole forming quality and construction efficiency， and keeps the full-hole core recovery rate stably meeting the design requirements. The research results not only provide a solid technical guarantee for the smooth implementation of exploration engineering in the mining area， but also offer a feasible technical reference for metal ore drilling projects with similar complex stratum conditions in western China.

Abstract:Drilling in littoral-shallow-sea sand layers faces complex construction environments and special stratigraphic conditions， significantly increasing construction difficulty. To address the construction challenges of drilling in littoral-shallow-sea sand layers， this paper analyzes the construction characteristics and environmental factors of drilling in sand layers， selects a rotary-table engineering drilling rig， and adopts bottom-hole impact drilling tools. It innovatively proposes a casing-while-coring technique featuring a "rotary-table-driven casing+in-hole wireline percussion+petal-type coring mechanism". At the same time， combined with a high-frequency vibrating hammer， the technique successfully solves problems such as difficulty in borehole formation and low core recovery rate in sand layers. Satisfactory application performance has been achieved in the sand-ore of littoral-shallow-sea areas，which provides a reference and guiding significance for future research and application of drilling and coring in littoral-shallow-sea sand layers.

Abstract:This paper systematically discusses the application value and technical route of air reverse circulation casing-following continuous sampling technology in low-grade mineral exploration of waste dumps. This technology integrated the techniques of air down-the-hole（DTH） hammer rock breaking， casing-following for wall protection， and reverse circulation sampling， and is suitable for complex unconsolidated strata with the advantages of high efficiency， precision， and environmental sustainability. Through the low-grade magnetite exploration project in the Xinjiang Jinbao waste dumps， the equipment selection， drilling parameters， and operational measures are analyzed in this research. The results indicated that this technology significantly enhances drilling efficiency and sampling representativeness， achieving an average mechanical efficiency of 24.28 m/h and an overall rock powder recovery rate of over 60%， which provides reliable technical support for resource exploration at waste dumps and holds significant potential for broader application.

Abstract:Waste drilling fluid is a primary pollutant generated during geological drilling. It features complex compositions containing drill cuttings， refractory organic matter， various chemical additives and other contaminants. Improper disposal will easily cause ecological pollution to soil， surface water and groundwater. To address environmental pollution arising from inadequate treatment of diverse wastes produced in drilling operations， this paper analyzes the pollution characteristics of waste drilling fluid. A harmless environmental treatment process combining "gel breaking， flocculation， decolorization and solid-liquid separation" is adopted. After treatment， the liquid phase meets direct discharge standards， while the separated mud cake can be solidified to satisfy the specifications for construction materials. The harmless treatment technology for waste drilling fluid was applied on-site in Gulang ZK301 hole to verify its technical feasibility. This study provides theoretical support and engineering references for the upgrading， iteration and large-scale application of harmless treatment technologies for waste drilling fluid.

Abstract:To implement the concept of green exploration， a recycling and harmless treatment system was developed for the 800 m3 waste drilling fluid generated during the construction of Xianglouye-1 well. The waste fluid is collected in a waste mud tank. After coarse solid particles are preliminarily separated by a desander， qualified slurry is returned to the drilling circulation system. Unqualified slurry is subjected to gel-breaking treatment by adding polyaluminium chloride （PAC） and anionic polyacrylamide （PAM）， followed by solid-liquid separation with filter press to produce mud cake and clean water. The clean water can be recycled or discharged up to standard， and the solid phase can be used for road construction or safely landfilled. Field application results show that 400 m3 waste drilling fluid and 200 m3 clean water of the whole well were recycled by this system， saving more than 160000 RMB in material cost directly. Zero pollutant emission was achieved， which provides a feasible technical scheme for environmental treatment of drilling fluid in shale gas exploration.

Abstract:In order to complete the evaluation of the gold resource potential of the Linglong-Shuiwangzhuang mining area， Zhaoyuan， two drill holes with a total of 4000 m coring task were designed and carried out in the relevant mining area. In the construction of ZK1603 hole， the research on solid-free anti-collapse drilling fluid based on polyvinyl alcohol（PVA） as an inhibitor was carried out， aiming at the problems of hole wall collapse， mud-making， and mud cake buildup on the inner wall of the drill pipe in the mudstone formations in the process of diamond wire-line core drilling. Compared with conventional inhibitors such as potassium humate and sulfonated asphalt， polyvinyl alcohol had strong inhibition， which was positively correlated with the degree of polymerization. Through comparative tests， it was determined that polyvinyl alcohol（PVA） was used as a viscosifying cutting agent， sulfonated lignite resin （SPNH） and sulfonated asphalt （FT-342） were used as water loss reducing agents to prepare the drilling fluid， which achieved good results in the actual practice.

Abstract:The Yila Mountain area in Xizang has complex geological conditions with extensive water-sensitive formations characterized by strong dispersion and sloughing. The strata primarily consist of altered ultramafic rocks with serpentinization， hydrotalcitization， and magnetitization， among which the serpentine content ranges from 63% to 84.4%， while the hydrotalcite content varies between 13.7% and 36.3%. The alteration zones occur repeatedly with thicknesses reaching hundreds of meters. During drilling operations， frequent issues happen such as borehole wall collapse， borehole shrinkage， sticking and burial of drilling strings， and low borehole completion rates， leading to frequent downhole accidents and severely affecting the drilling efficiency. Based on the analysis of rock and mineral composition， this paper examines and summarizes the impact of such highly dispersible and easily sloughing strata on drilling operations. Through comparative analysis of the performance and on-site application effects of traditional PHP drilling fluid， low-solid anti-collapse drilling fluid， and the FCM environmentally friendly film-forming drilling fluid， an optimal environmentally friendly film-forming drilling fluid system suitable for such strata was selected and successfully applied in four boreholes. This effectively improved drilling efficiency and yielded favorable application results. Additionally， combined with engineering practice， drilling techniques such as casing while drilling for reaming and drilling fluid solid-phase control tailored to such highly dispersible and easily sloughing strata were summarized， providing references for similar strata construction.

Abstract:To address the frequent technical challenges of borehole collapse， block falling， and pipe sticking encountered in multiple drill holes penetrating fractured formations in a mining area of Nandan County， based on a systematic analysis of the geological characteristics of the mining area， this study proposes technical countermeasures to wellbore stabilization using flushing fluid， and field application was carried out. Influenced by the Danchi fault zone， the siliceous mudstone rock mass exhibits extremely developed joints and fissures， displaying hard-brittle fractured characteristics. Under mechanical disturbance， the interlayer structure is highly susceptible to instability failure， forming brecciated and fragmented spalled materials which further trigger large-scale block falling and collapse-induced pipe sticking. Therefore， multiple flushing fluid formulations were explored， including low-solid plant gum systems， low-clay-phase silicate anti-collapse systems， and low-solid film-forming systems. Ultimately， a low-solid film-forming PAC-LV+PVA1788 flushing fluid system suitable for the fractured formations in this mining area was developed. The system utilizes the skeleton role of clay particles within the low-solid-phase system. Under the GSP dispersion and activation， PAC-LV particle bridging and PVA1788 hydrophobic anchoring synergistically form a film， rapidly generating a dense and tough internal/external mud cake on the siliceous mudstone borehole wall. This system combines the dual functions of physical plugging and chemical consolidation， effectively solving the engineering challenge of long-term micro-fracture plugging in hard-brittle fractured formations. Field application has yielded favorable results， providing strong technical support for the prospecting breakthrough of critical metals such as tin， antimony， and indium in Guangxi.

Abstract:After more than 20 years of production， the pressure coefficient of the main pay zone （First and Second Member of Feixianguan Formation） of Puguang Gas field has been dropped to 0.60~0.70. However， the overlying Third Member of Feixianguan formation and underlying Changxing Formation are still maintaining virgin formation pressure with the pressure coefficient of 1.20 and 1.10 respectively， which forms a relatively high-low-high pressure system. The second intermediate casing penetrates through the Third Member of Feixianguan formation. If conventional low-density water-based mud with a density of 1.03~1.05 g/cm3 is adopted in the under-pressured intervals of the First and Second Member of Feixianguan formation， severe drilling complications such as lost circulation， differential pressure sticking and formation damage to the main pay zone may still occur. To avoid adverse impacts on production， in this paper， a feasibility analysis was carried out covering lost circulation prevention， plugging， operational depth of 5115 m and sealing while-drilling， it is recommended that the formation should be penetrated by combining fuzzy-ball drilling fluid with sealing while-drilling technology.

Abstract:Aiming at the difficulties faced by in-situ leaching mining of uranium deposits in deep and complex formations of Honghaigou， Xinjiang， such as low drilling efficiency， high cost and strict well completion requirements， this paper conducts a study on high-quality and rapid drilling technology. By comparing the performance and drilling efficiency of three types of equipment， namely water well rigs， engineering rigs and petroleum rigs， the applicability of different equipment is clarified. Meanwhile， drill bit selection， environment-friendly low-solid anti-sloughing drilling fluid， deviation control technology， casing structure and slotting completion technology are optimized. A total of 19 boreholes were constructed on site with a total footage of 13731 m， and all construction indicators met the design requirements. Results show that crawler-type deep well rigs are suitable for deep drilling； the optimized composite casing program achieves both stability and economy； PDC bits， environment-friendly drilling fluid， PVC casings and cutting and windowing completion technology can improve drilling efficiency， protect formation permeability and extend well service life. The established high-quality and rapid drilling technology system effectively solves construction challenges caused by deep burial， complex formations and special requirements of in-situ leaching， providing technical support for efficient and green exploration and development of Honghaigou and similar sandstone-type uranium deposits.

Abstract:The wellbore serves as the pathway for CO₂ injection into the target formation and constitutes the fundamental basis for long-term monitoring and research on both the CO₂ injected into the formation and its impact on it. Compared with conventional geothermal drilling， the wellbore of CO₂ geological storage in deep saline aquifers requires higher standards of sealing and corrosion resistance. This study takes the first CO₂ geological storage project in deep saline aquifers in Shandong Province as an example， the difficulties in drilling construction are listed， the main technical countermeasures are offered， and guidance for drilling construction of other CO₂ geological storage projects in deep saline aquifers is provided. The research results show that during the drilling construction process， the rapid drilling and corresponding mud wall protection technologies are adopted to solve the problem of poor wellbore stability. The difficulty of core sampling was solved by adding a spring clip device to prevent core from falling at the bottom of the coring tube. High-strength casing is used to solve the gas tightness and safety problems of the casing. The integrated technology of cementing， perforating and well completion using BCE-750S anti-corrosion cement is adopted to solve the problem of cement corrosion. By adding the slips packer device to the CO₂ injection pipe string， the gas tightness and stability of CO₂ injection are guaranteed. At the same time， the oil wellhead device in the oil production field is adopted， and a pressure monitoring instrument is installed to solve the long-term pressure-bearing and monitoring problems of the wellhead device.

Abstract:In view of the large uncertainty in the analysis of the characteristics of borehole water gushing layer in geothermal exploration， based on the limitations of conventional comprehensive logging， this paper focuses on the working principle and technical advantages of ultrasonic imaging logging while drilling. The analysis of its application in MD-01 geothermal well shows that the technology can directly identify the formation structure characteristics of the water gushing layer in the borehole wall， and can externally characterize the characteristics of open hole wall fractures， local holes and complex fracture zones. The feasibility and accuracy of the ultrasonic imaging logging while drilling technology can be verified as the basically same results with the conventional comprehensive logging under the same borehole wall characteristics. This logging technology can effectively improve the limitations of the conventional comprehensive logging， greatly shorten logging operation cycle， significantly improve logging efficiency and cutting the logging operation cost， which has popularization and application value in deep geothermal horizontal well logging.

Abstract:During the drilling of geothermal wells in the Langjiu Geothermal Field in Ngari， Xizang， multiple challenges were encountered such as fractured and collapsed strata， early water blowouts/gush， difficulties in maintaining pressure balance with mud wall protection while drilling， high difficulty in temporary water shutoff with intermediate casing， frequent scaling and malfunction of ram BOP， and inadequate safety protection for personnel at the wellhead. By developing and applying the wellhead blowout preventer diversion device， the dual-hanging water-shutoff device for intermediate casing， and the wellhead valve replacement device for the high-temperature wells， the above difficulties have been effectively addressed. It not only ensures the completion and production of geothermal water from shallow aquifers but also enables drilling through deep geothermal layers， achieving multi-layered geothermal water production with a single borehole.

Abstract:Geothermal drilling construction is a rigorous work with high professional requirements， and the matched equipment and process tools are the guarantee for the smooth progress of construction. It is critical to improve the professional quality of the team and the technical capacity of the unit， as well as adopting advanced technology under the new situation. In addition， China''s geothermal market is expanding toward the deep strata， which brings increasing construction difficulties. Construction enterprises with proprietary construction technologies and characteristics can maintain development momentum and gain competitive advantages in the market. This paper analyzes some specific problems in geothermal well construction， and points out that multi-process air drilling is an effective method for high-quality and efficient exploitation of deep geothermal and groundwater resources.

Abstract:Magnetic guidance is a mature intersecting method applied in solution mining of trona via directional intersecting wells. However， when pyrite susceptible to magnetization exists in strata， the pyrite will be magnetized and turn into a strong magnetic body during the well intersection stage. On one hand， prolonged exposure of non-magnetic drill strings to strong magnetic environments degrades the magnetic shielding performance， causing azimuth errors in MWD measurement. On the other hand， if the target cannot be hit at the first attempt during magnetic target hitting in the horizontal section， magnetic anomalies will completely invalidate the magnetic azimuth measurement of MWD， and no azimuth data will be available to guide sidetracking for the second target hitting. The horizontal gyroscope can be adopted to measure non-magnetic drill strings in the deflection section and calibrate the MWD azimuth data. It determines the azimuth independent of the geomagnetic field in the horizontal section， providing data support for subsequent drilling and sidetracking for secondary target hitting. In several domestic trona intersecting wells， horizontal gyroscope logging was adopted. Well interconnection was successfully achieved for multiple intersecting wells with a target width of approximately 152 mm under strong magnetic interference. The results verify the feasibility and reliability of horizontal gyroscopes under such working conditions.

Abstract:The air DTH hammer casing-following drilling technology presents prominent advantages in complex formations drilling. Aiming at the frequent blockage of orepasses that seriously endangers mine safety production， this study takes the severe ore blockage occurring in No.1 orepass of a limestone mine for cement production in Dujiangyan as the research object， combined with the requirements for drilling blasting holes to clear orepass blockages， multiple types multi-dimensional drilling schemes for blasting holes are proposed， including long-distance inclined holes， near-end vertical holes and near-end inclined holes based on the rapid drilling technology of air DTH hammers. Field application results show that the near-end inclined holes were successfully drilled through the blockage sections using concentric DTH hammer casing-following with directional and straight-hole maintaining performance， and the rapid construction of high-precision blasting holes realized effective orepass clearing. For the ZK5 blasting hole， the average drilling rate reached 8 m/h at the interval of 0~68 m and 15 m/h at 68~143 m. The overall drilling efficiency was greatly improved compared with conventional drilling methods. Although open-hole drilling with air DTH hammer achieves fast hole-making， however， swing of the bottom hammer tends to induce significant hole deviation. Drilling trajectories are especially prone to deflection in inclined holes under the effect of gravity and weight-on-bit. Accordingly， an in-hole data acquisition and analysis system is recommended in follow-up research to realize real-time downhole-surface interaction and borehole trajectory control. This study verifies that the concentric air DTH hammer casing-following drilling technology can achieve efficient and precise orepass clearing， providing a solid technical reference for the treatment of orepass blockage in mines.

Abstract:In response to the strategic demand for groundwater resource exploration in the hinterland of the Taklamakan Desert in southern Xinjiang， this study takes exploration borehole KT1 in the Andir work area as the engineering carrier. A full-process technical system for 500 m-deep layered pumping test wells with the philosophy of "coring first， well completion later" is systematically established， enabling integrated implementation of accurate identification of deep loose thin interbedded strata， dynamic well design， high-precision layered water shutoff and Packer-based layered pumping tests. By integrating multi-source data including core samples， well logging， grain size analysis， soluble salt tests and pumping tests， the aquifer system is precisely delineated， hydrogeological parameters of each layer are obtained independently， and the vertical differentiation law of groundwater quality is revealed. Engineering practice demonstrates that the proposed technical system can effectively tackle technical challenges including deep borehole drilling in desert areas， borehole wall stabilization in silty-fine sand strata， water shutoff for thin interbeds， and parameter acquisition for low-permeability layers. A multi-aquifer monitoring and production well is constructed， providing a replicable technical paradigm and data support for precise groundwater exploration in arid desert regions， and carrying great significance for water resource security in border areas.

Abstract:Due to instrument sticking and a previous failed fishing operation， a fluid observation well at a volcanic monitoring station was left with various complex fish， such as drill pipes and cables. Furthermore， the operation was strictly constrained by the high-altitude scenic location and environmental protection requirements. To address these complex well conditions， a downhole television system was used to accurately locate the top of the fish， and a combination of techniques-fishing， back-off， milling， and washover milling-was applied for well remediation. During the operation， external force was applied to increase torque， and a left-hand tapered tap was used for thread making and back-off， successfully backing off the stuck drill string. A customized washover tool with a wire-reel barrel was developed and innovatively modified （by welding steel bar hooks on its inner wall） to clear entangled cables and assist in fishing the drill tools. Finally， pin joint connection fishing and external hook fishing were employed to recover the remaining cables. Meanwhile， a high-viscosity drilling fluid was formulated for cuttings removal， and a closed-loop system was established to achieve zero discharge of drilling mud. As a result， all downhole fish were successfully retrieved， including a total length of 173.44 m of stuck drill pipes， along with all cables， instruments， and fishing hooks， achieving a 100% fishing success rate. The wellbore sustained no secondary damage， the function of the observation well was fully restored， and economic losses of nearly 2 million RMB were saved. This study provides referable technical approaches and practical experience for the fishing and remediation of complex fish in similar troubled wells.

Abstract:To address the engineering challenge of borehole collapse or even ground subsidence induced by total mud loss when drilling into the bedrock surface in deep-buried karst areas， this study systematically investigates the collapse mechanism and preventive measures through a combination of theoretical analysis and engineering verification， based on three borehole collapse accident cases in Tongzhou District， Beijing. Based on Rankine’s earth pressure theory， a stress balance model of the borehole wall before and after mud loss is established， and a formula for calculating the critical depth to maintain borehole wall stability is derived. The results indicate that the fundamental cause of borehole wall instability is the decrease in hydrostatic pressure caused by total mud loss， which fails to balance the lateral earth pressure of the formation. The collapse modes can be classified into local collapse and overall collapse. The former occurs from top to bottom above the critical depth due to insufficient hydrostatic pressure， while the latter requires extreme geological conditions such as a fractured bedrock roof， well-developed karst caves or underground rivers， and an overburden dominated by non-cohesive soils. Engineering practice demonstrates that preventive measures， including the rational design of conductor casing depth， small-diameter pilot drilling， and advanced casing running， can effectively avoid collapse accidents. These research findings provide important guidance for drilling safety in karst areas with deep overburden.

Abstract:In core drilling projects， casing wall protection technology can ensure the stability of the hole wall. However， after completion， due to problems such as water expansion of the stratum and rock spalling， the casing often cannot be pulled out， resulting in resource waste and economic losses. As a core tool for casing recovery and in-hole accident handling， the cutting efficiency of the hydraulic cutter depends on the matching degree between the performance of the carbide cutter-bit and workpieces as well as its adaptability to working conditions. Combined with two field cases， namely the stuck-drilling accident treatment in Laiwu of Shandong and casing pulling operation in Baise of Guangxi， this paper systematically investigates the matching rules between cutter-bit properties and manganese-steel drill pipes as well as conventional casings by comparing cutting performance of YG-series， YT-series and YW-series cemented carbide bits. In view of typical failure modes including bit chipping and iron-chip jamming observed on actual failed components， three primary failure causes are summarized， that is improper material selection of cutter-bits， inappropriate cutter extending speed， and unreasonable cutter grinding status. YW2 for manganese-steel drill pipes and YT5 for high-strength casings are proposed as the priority selection schemes. The application prospect of cubic boron nitride （CBN） bits is also discussed. This study provides practical references for rational bit selection and cutting-process optimization of hydraulic cutters， and possesses important guiding significance for improving pipe recovery rate in drilling engineering.

Abstract:During the CPT static borehole testing operations conducted by the Ocean Geological Survey No.17 drilling vessel in the offshore area， long-term retention of drill pipes in the borehole caused borehole wall instability and collapse， resulting in issues such as pipe sticking and pipe burial during tripping out. Based on the equipment and technical methods employed in this engineering case study， this paper conducts an applied research on the combined application of centralizer and hydraulic internal cutter， provides a detailed exposition of the internal structure and operating principle， as well as practical experience gained in handling borehole-related incidents， which can serve as valuable references for addressing similar accidents.

Abstract:The construction of a three-dimensional comprehensive observation site for cross-fault deformation involves deploying multiple observation methods across the "surface-shallow-deep" layers along the same active fault. Relying on core construction techniques such as precision casing wall protection， precise control of borehole inclination， and deep wireline coring， a high-quality three-dimensional observation system is established. This forms a "three-dimensional array" characterized by high density， multi-frequency， and synchronous monitoring， capable of real-time detection of transient fault movements and long-term tracking of chronic strain accumulation. Drawing on the construction practices of the Cross-Fault Deformation Comprehensive Observation Site Project in Linyi City， Shandong Province， this paper introduces the construction technologies for two continuous observation stations， three comprehensive fault deformation observation piers， and one set of fault plane Newtonian force monitoring systems， ultimately establishing a three-dimensional comprehensive observation site for cross-fault deformation. The implementation of this project not only helps improve regional earthquake early warning capabilities and mitigate the losses caused by earthquake disasters， but also provides valuable data support for scientific research in fields such as geology and seismology， thereby promoting the development of related disciplines.

Abstract:As a key facility of the Beijing-Tianjin-Hebei flood control system， the Beijuma River Regulation and Storage Project faces three major technical challenges in foundation pit dewatering： highly permeable pebble strata， complex riverside boundaries， and the ineffectiveness of traditional water inflow prediction methods. In this study， a triple cross-validation method combining pumping tests， foundation pit dewatering tests and numerical simulation is adopted to realize accurate inversion of hydraulic conductivity. Initial parameters are obtained through pumping tests of dewatering wells； the feasibility of high-intensity pumping and drainage is verified by a collaborative open drainage system with 36 wells during foundation pit dewatering tests. A three-dimensional seepage model is built on the GMS platform， and the hydraulic conductivity is determined via inversion using a water level residual feedback mechanism. The study verifies that for deep foundation pits in pebble strata， the numerical simulation-driven parameter inversion method can accurately characterize complex boundaries and realize closed-loop verification between parameters and dewatering effects， providing a scientific basis for water inflow prediction.

Abstract:Aiming at the non-standardized problems in equipment layout， pipeline laying， protection facilities and marking system of drilling rig， the Quality Control Circle （QC） method is used to construct the standardized index system of rig through the analysis of current situation， causal identification and key factor control， and to formulate standardized measures such as equipment layout， pipeline laying， safety protection and visual marking. After pilot verification， the space organization， line order， safety protection and regional identification of the rig are significantly improved， and the safety and efficiency of the operation are improved. Through institutionalized documents and inspection mechanisms， the transformation of empirical results to the standard system is realized， and a replicable standardization implementation framework is formed. The research shows that the "QC" method can effectively promote the standardization of management in the complex environment of field drilling， and provide a feasible technical path and implementation framework for the standardization of geological drilling sites.