Abstract:The high- water jet technology has the superiority of the wide range of working medium and environmental protection, and can be used to break the submarine gas hydrate formations. In this paper, LS-DYNA finite element program is used to simulate the fragmentation process of submarine gas hydrate formations with high-pressure water jet under submerged condition. The effects of four key parameters (jet velocity, nozzle diameter, target distance and incident angle) on the erosion volume of hydrate formations are studied. The following conclusions are drawn: the fragmentation of hydrate sediments needs to meet the requirement that jet velocity is higher than the critical velocity; the erosion volume gradually increases with the increase of jet velocity; the increase of nozzle diameter will lead to the increase of the radial erosion volume of formations, thus increasing the overall erosion volume; the increase of target distance will increase the energy loss of water jet in the process of water movement, leading to the decrease of erosion volume; the erosion volume will increase first and then decrease with the increase of nozzle incidence angle, eventually tending to be stable. When the incident angle is 10°, the erosion volume can reach the maximum value.

Abstract:In order to cope with the difficulty in maintaining the borehole verticality and core recovery due to great alternation of strata, liquefaction of soft strata and sand, poor cementation and loose structure of sand encountered in drilling of the standard 200m geo-technical investigation boreholes in the Xiongan New Area, comprehensive measures such as proper configuration of the drilling string, optimization of drilling parameters have been adopted to prevent drilling deviation. At the same time, effective technical measures such as dry core drilling in loose strata, isolation in core barrels, diversion of the mud pump discharge for core ejection have been adopted to ensure the drilling quality, leading to very obvious technical results.

Abstract:This paper focuses on the research and application of anti-high temperature seawater drilling fluids additives and systems at home and abroad,some suggestions for the research directions of key technologies of high temperature seawater drilling fluids are put forward. The future direction researches of ultra-high temperature seawater drilling fluids technology is high temperature and salt resistant drilling fluids additives(such as：salt - resistant filtration reduction agent、tackifier、Anti - collapse inhibitor、lubricant), systems, testing instruments, environmental protection, etc.

Abstract:Drilling leakage is not only a common phenomenon, but also one of the important factors that affect drilling safety and penetration rates. This paper studies the mechanism of severe leakage, plugging measures, plugging materials and technology, and analyzes the severe leakage problems and countermeasures in drilling at home and abroad. Meanwhile, the methods to treat the severe drilling leakage at home and abroad are summarized, and its advantages and disadvantages are also analyzed. The new technologies to solve the karst cave leakage can be summarized into three major categories: the polymer gel plugging, chemical plugging and cement plugging. Moreover, this paper emphatically introduces the lab testing and field application results of a new chemical gel plugging technique and an intelligent gel plugging technique, with the success rate of field application up to 98%.

Abstract:Jiaoye 197-4HF was a three-section long reach horizontal well drilled from the No.197 platform in the Fuling Pingqiao Shale Gas Field. The long horizontal section of the well was located in the shale member of Longmaxi Formation in Silurian. Great challenges were faced in drilling: (1) It was easy to form cuttings beds over the long horizontal section with high torque friction; (2) The shale was easy to hydrate and expand, resulting in wellbore instability; (3) Micro-fissures were developed in shale formation, leading to large loss of drilling fluids. In order to ensure the normal drilling operation, the appropriate formulation of the oil-based drilling fluid was optimized through indoor comparative experiments in the early stage. Field application showed that the optimized drilling fluid formulation fully met the requirements of the field work, achieving safe and smooth completion of the third-section horizontal drilling.

Abstract:The heterogeneity of the sand-shale interbeds in the lower part of the oilfield produced strong vibration of the downhole drilling string, leading to short life of PDC cutting teeth and easy hole deviation. At present, PDC drill bits are designed with 5 blades or 6 blades with 16mm cutting teeth to reduce the downhole tool vibration to ensure the life of the PDC bit, but the drill bit aggression is reduced and the mechanical drilling speed is lower. Based on the characteristics of lower formation in KKM Oilfield, a 4-blade 19mm composite PDC bit was selected. The drill bit provided high rock breaking efficiency and aggression capacity, which can greatly increase ROP. At the same time, through the bottom hole assembly dynamic analysis, the bisector + single stable single bending (0.5°) drilling tool combination was optimized. The application of three stabilizers can achieve strong vibration reduction effect, which can effectively improve the anti-deviation ability and reduce the downhole vibration with the small-angle downhole motor tool, and also with large-size PDC bit, the goal of drilling the lower section in one run was achieved. The ROP was increased by 115.35%.

Abstract:The uncertainty of fishing schedules makes operation costs uncontrollable, and it is of vital importance to formulate a proper economic decision point. This paper takes a certain fishing well in Bohai Oilfield as an example. Sidetracking from above the fish was necessary without fishing, or from below the casing shoe with fishing. Abandoning fishing or fishing blindly was not the most economical solution. The two concepts i. e., the economic operation period and the decision-making period, were proposed by quantifying the fishing period. Through field fishing attempts, the difficulty of the operation was analyzed during the decision-making period, and it was determined whether the operation can be completed within the economic period; thus minimizing overall operation costs and improving economic benefits of oilfield development. This decision-making method was applied at Well A in Bohai Oilfield, saving a total of nearly 4.2 million. The calculation method for the economic fishing period and the decision-making period proposed in this paper is worthy of promotion.

Abstract:In the downhole operation of oil, gas and water wells, the ball is widely used for pipe pressure testing, sealing and multi-stage (layer) fracturing. In order to accurately calculate the time when the ball arrives at the design point (i. e., the waiting time), the new formula of the waiting time calculation is developed by analyzing the movement process and the forces of the ball. It is pointed out the key factors affecting the waiting time include the coefficient of resistance around the ball, the ball diameter and density, and fracturing fluid properties, which provides a basis for optimizing the construction design. At the same time, a new type of tubular pressure test body that can reduce the waiting time and backwashing time is proposed, laying the foundation for further construction optimization.

Abstract:The curtain grouting project of No. I ore body of Great Wall Gold Mine in Qian’an is of a large-scale, and the geological structure of this mine area is complex. When curtain drilling entered the ultra-hard “slippery” dolomite stratum, the penetration rate became low, which greatly affected the construction schedule. Therefore, various construction technologies have been tested for this stratum in the drilling process, and with the analysis based on the data collected about drill bit types, drilling technologies and drilling parameters in the real drilling process, the most effective drilling methods have been established, which can provide good reference for future prospecting and the second stage curtain drilling project in this area.

Abstract:The prize fish green cultivation project of Rizhao Wanzefeng Fishery Co., Ltd. at Yellow Sea Cold Water Mass is one of the first major projects for upgrading of the old development mode to the new one in Shandong province. The planned marine area is 20km2. Site investigation is the first basic work for the construction project, and also the important basis of project site selection, design and construction. With effectively utilizing limited resources, proper verification, careful construction, innovative renovation of the drilling ship, and placement of the deep-sea casing with the gravity guide device, site investigation was successfully completed for the project, providing experiences for offshore deepwater investigation works.

Abstract:The offshore drilling platform is important facility for offshore geo-technical investigation and mineral exploration. There are many types of offshore drilling platforms, and selecting a suitable one can get twice the result with half the effort. The modular shallow sea drilling platform provides powerful functions and a wide applicable range due to its many advantages such as easy manufacture, short manufacture period, low cost, convenient transportation, efficient installation, high mobility. In this paper, the design and manufacture of the modular shallow sea exploration platform are introduced, and its advantages are analyzed and summarized based on three application cases, which provides a reference for offshore drilling operations.

Abstract:The bearing capacity of large diameter piles in Dalian is simulated with FLAC3D software, and the bearing capacity of conventional piles and bell-out piles are compared and analyzed. The results show that the FLAC3D software simulated changes in Q-s curves fit the actual measured ones for conventional piles under the same load, indicating that the established FLAC3D model is suitable for study of those piles. The FLAC3D model is used to analyze stress of bell-out piles and conventional piles under the condition of 6000kN load and the same pile diameter. Under the condition of the same stress at the top of pile, the stress at the end of pile is reduced by 50%, and the stress condition at the end of pile is improved. Under the condition of the same pile length, the bearing capacity of the bell-out pile with reduced diameter is studied. The material used is 61.2% of the conventional pile. The simulation results show that the bell-out pile with reduced diameter can meet the engineering load requirements and reduce the cost. It is suggested that the original design should be revised to provide a theoretical basis for similar projects.

Abstract:Soft ground treatment affects the quality, investment and progress of the whole project, and its importance has been recognized by more and more people. Based on the principle of three-dimensional drainage consolidation and the pull-out force of the pile itself, the 3-D consolidated cylinder was used for once-for-all rapid drainage consolidation of saturated soft ground without external load, improving the shear strength, compression behavior, water permeability and dynamic characteristics of ground.

Abstract:The relationship between the jacking force and the maximum vertical bearing capacity of a single pile is introduced with a method of estimating the maximum vertical bearing capacity of a single pile by use of the jacking force. In the stage of trial piling, friction piles in the saturated soft soil provide a low bearing capacity, since the bearing capacity of the pile is mainly determined by the frictional resistance on the pile sides after the soil is restored. According to results obtained from the static load test, a coefficient called pressure ratio can be derived through dividing the maximum vertical bearing capacity of a single pile by the jacking force on piles. By comparison, the normal pressure ratios are obtained for the Kunming area, which falls between 1.3 and 2 in the case of jacked prefabricated pipe piles, and between 2.5 and 5 in the case of jacked prefabricated square piles. The maximum vertical bearing capacity of a single pile can be estimated with multiplying the jacking force by the pressure ratio. The influence of the soil compaction effect and the excessive pore water pressure on the bearing capacity of piles is briefly introduced. Soil and pore water in the stratum are compacted in sinking the engineering piles, generating the pore water pressure which creates an upward buoyancy and causes the constructed piles to float; thus reducing the bearing capacity of the single pile.

Abstract:The pile-anchor supporting structure system is a supporting method which combines slope protection piles with soil anchor bolts. It is widely used in slope and deep foundation pit support due to its safety and economic characteristics. However, its application in ultra-deep foundation pits is still under exploration. According to the engineering geological conditions and hydrogeological conditions at the foundation pit of Fengcheng International Trade Project, taking into account of its surrounding conditions, and with comparison of several different foundation pit support plans, the pile-anchor supporting system was selected, which is technically feasible, economically reasonable, provides good overall performance and is convenient for the excavation of foundation pits and subsequent construction. Then the soil pressure calculation, cast-in-place pile design, anchor bolt design and stability checking calculation were carried out for the foundation pit supporting structure. Later deformation monitoring verified that the pile-anchor support was safe, economical and feasible for the ultra-deep foundation pit.