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沁水盆地深部复杂结构煤储层钻完井及压裂工艺研究

Study on drilling and fracturing technology for deep complex structurecoal reservior in Qinshui Basin

  • 摘要: 为了探求适于深部复杂结构的煤储层中煤层气高效开发工艺,以沁水盆地柿庄北区块为例,基于水源钻机定向井组开发过程中,实施的PDC钻头+螺杆钻技术、低固相聚合物钻井液、煤层段“低排量、低转速、低泵压”钻进、小井组同步水力波及压裂等工艺实践,探讨了构造复杂的深部煤层钻进过程中,引起井内煤壁段坍塌的主要因素,优化了钻完井、水力压裂工艺参数。研究表明钻井液入侵与压力波动是影响煤壁垮塌的主要原因,分段钻井液性能和煤层段最佳钻进参数:钻压20~30 kN,转速25~30 r/min,排量16~18 L/s;采用小井组同步水力波及压裂工艺可以形成有效的裂缝延伸,有效裂缝长度为250~350 m。研究认为,施工至复杂煤体结构的煤层段时在调整好钻井液性能的基础上,采用“低转速、低泵压、低排量”平稳钻进,且可根据井距采用单井压裂+同步水力波及压裂的组合施工,以获得最佳的压裂效果。

     

    Abstract: In this paper, an efficient development technology for coalbed methane for complex coal structure in deep mines is proposed. The application of this technology was conducted on northern Shizhuang region of Qinshui basin. This technology is based on the practice of PDC bit cooperating with screw drill, low solids polymer drilling fluid, drilling with low displacement, low rotational speed, and low pump pressure in coal seam, and synchronous hydraulic fracturing in small well group during the development of directional well group with the water source drill rig. The main factors that cause coal wall to collapse when drilling deep coal seams with complex coal structure were discussed. Then the drilling and hydraulic fracturing parameters were optimized. The study shows that the main factors that cause coal wall to collapse are the drilling fluid invasion and pressure fluctuation. The drilling fluid performance in different formations and drilling parameters can be optimized when the drilling pressure is 20~30 kN, rotational speed is 25~30 r/min, and displacement is 16~18 L/s. The effective fracture extension can be formed by using synchronous hydraulic fracturing technology of small well group, and the effective fracture length was 250~350 m. The study results suggest drilling with low speed, low pump pressure and low displacement to ensure stable drilling for coal seam with complex coal structure. The best fracturing effect can be achieved by applying the combination of single well fracturing and synchronous hydraulic fracturing according to the well spacing.

     

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