定向钻进连续取心钻具设计及取心参数仿真分析

Design and simulation analysis of continuous coring parameters in directional drilling

摘要:

在战略性矿产资源勘探取样过程中,传统的垂直孔面临着单孔投资高、获取地质信息有限等难题,无法满足高效增储勘探的需求。为此,基于绳索取心和定向钻井技术,设计了一种定向钻进连续取心钻具,能够高效精准的获取地下三维空间的地质岩心。针对该技术在硬岩中钻进效率低、钻具易折断、岩心难以连续获取等技术难点,采用仿真模拟的方法分别研究了钻压、转速、造斜率对定向取心钻进的影响。仿真分析结果表明,钻压、转速与钻进速度、造斜率和弯接头应力成正比,当钻压大于30 kN、转速大于230 r/min时即可满足6°/30 m的造斜需求。综合考虑钻具使用寿命,优选钻压为25~30 kN,转速为230~300 r/min。随着造斜率增大,岩心与岩心管之间的接触应力也随之变大,但最终的接触应力会保持在稳定范围内。当造斜率为9°/30 m时,最大的接触应力为514.7 MPa,均小于岩心管材质的屈服强度。上述仿真模拟为定向钻进连续取心钻具的钻进参数与造斜能力协调优化提供理论支撑。

Abstract:

In the process of strategic mineral resources exploration and sampling, the traditional vertical hole faces some difficulties, such as high investment in a single hole and limited access to geological information, which cannot meet the needs of high efficient exploration. Therefore, the directional continuous coring technique is proposed based on wireline coring and directional drilling technology, which can efficiently and accurately obtain geological cores in underground three-dimensional space. To solve the technical difficulties of low drilling efficiency in hard rock, complex force on drilling tools and difficulty in continuous core acquisition, the effects of weight on bit and rotation speed on drilling efficiency, drilling speed and build-up rate on directional coring were studied by simulation. The simulation analysis results show that the weight on bit and rotation speed are proportional to the drilling speed, build-up rate and bend-joint stress. When the weight on bit is more than 30 kN and the rotation speed is more than 230 r/min, the build-up rate of 6°/30 m can be satisfied. The formation stress under the action of weight on bit is more concentrated and the extension depth is small, while the formation stress distribution under the action of rotation speed is wide, reflecting different rock breaking effects. Based on the comprehensive consideration of drilling tool life, the preferred weight on bit is 25~30 kN and the preferred rotation speed is 230-300 r/min. The contact stress between the core and core tube becomes larger with the increase of build-up rate, but the final contact stress will be kept within the stable range. The maximum contact stress was 514.7 MPa at build-up rate of 9°/30 m. This contact stress was less than the yield strength of coring tube. The above simulation provides theoretical support for the coordinated optimization about drilling parameters and deviation capacity of directional continuous core drilling tools.