煤层气储层伤害机理与水平井双层管柱筛管完井技术

煤储层具有高吸附性、低渗透性、易压缩与易破碎的特征，煤层气水平井钻完井过程中常常造成煤储层伤害，导致煤层渗透率和单井煤层气产量大幅度降低。通过实验分析，揭示水平井钻完井液中的固相颗粒、流体流动诱导产生的固相成分对煤储层微裂隙堵塞成因，阐明煤层气水平井钻完井中储层伤害的机理。在此基础上，提出水平井双层管柱筛管完井技术，分析其减轻煤储层伤害的机理，即通过冲管水力冲击作用消除水平井壁钻井液泥饼，清除井壁附近堵塞微裂隙煤粉，并在近井地带产生应力增渗作用。相对于煤层气常规的多分支水平井及分段压裂水平井，水平井双层管柱筛管完井的稳定日产气量、稳产周期均大幅提升。该技术在沁水盆地南部部分区域推广应用显示，3号煤层气井平均日产气量提升到20 000 m3，同时实现15号煤层气的开发突破，平均日产气量提升到10 000 m3以上。研究成果对于降低煤层气水平井钻完井过程中的储层伤害，提高煤层气井产量具有重要的理论和实践意义。 

Damage mechanism of CBM reservoirs and double-layered screen pipes in the horizontal well completion

Coal reservoirs have the characteristics of high adsorption, low permeability, easy compression and easy breakage. At the drilling and completing stage of horizontal coalbed methane wells, coal reservoir damage often occurs and leads to a significant reduction in coal seam permeability, thereby resulting in single well production. Through experimental analysis, the solid phase particles in drilling and completion fluids for horizontal well and the solid phase components induced by fluid flow are found to block the micro-fractures in the coal reservoir, and the damage mechanism for coal reservoir is elucidated to the drilling and completion reservoir of the horizontal well of coal-bed methane. On this basis, the completion technology for horizontal well is proposed with double-layered screen tube to analyze the mechanism of mitigating the coal reservoir damage, the mud cake of horizontal well wall drilling fluids is eliminated by the hydraulic impact of the flushing pipe, the micro-fissure pulverized coal near the well wall is removed, and the stress and permeation effect is generated in the near well zone. Compared with the conventional multi-branch horizontal wells and segmented fracturing horizontal wells of coalbed methane, the stable daily production and stable production period have been greatly improved with the double-layered screen pipe in the completion of horizontal wells. The application of this technology in some areas of the southern Qinshui Basin shows that the average daily output of No.3 coalbed methane well has increased to 20 000 m3. Moreover, a significant breakthrough has been made in the development of No.15 coalbed methane with the average daily output increasing to more than 10 000 m3. The research results have important theoretical and practical significance for reducing reservoir damage during the drilling and completion of coal-bed methane horizontal wells and enhancing the production of coal-bed methane wells.