复杂煤体结构煤储层水平井复合管柱完井方法研究

Study on horizontal completion with composite tubular string in coal reservoir with complex coal structure

针对煤体结构破坏变形程度差异性与物理特征非均质性强,水平井眼钻遇煤储层的煤体结构复杂,单井完井与增产技术方法单一等问题,为了实现水平井分段完井与适应性增产,提出了复杂煤体结构煤储层水平井复合管柱完井技术,设计了外层套管与筛管复合完井管柱、内层作业油管柱与配套分段完井工具,完善了双管柱受力和相关水力计算模型。在山西省阳泉地区15号煤层开展了复合管柱完井现场试验:将长度为659.5 m的复合管柱下入水平井中至1591 m井深,煤层水平井眼被封隔为4段,采用双管柱结构完成了水力循环解除管柱遇阻、洗井、胀封管外封隔器及煤层分段完井等作业环节的现场测试。基于该试验水平井的工程数据,采用有限差分法计算了双管柱受力,并进行了相关水力计算,结果表明:内层管柱增加了完井管柱下入过程中的侧向力,井下管柱与井壁之间的摩擦阻力增加了5642.75 N。喷头压降与内层管柱水力循环压耗是影响井下双管柱水力循环压耗的主要因素,双管柱下入过程中水力循环排量控制在16~20 L/s,以清除井眼内固相颗粒及维持井壁稳定;洗井作业时排量提升至20~24 L/s,以消除井壁煤层的钻井液伤害。通过研究与现场试验,证明了煤层气水平井复合管柱完井技术具有先进性和可行性,为复杂煤体结构煤储层水平井多样化与适应性增产改造工程提供了可靠的作业基础。

Aiming at the problems such as large deformation difference of coal structure,strong heterogeneity of physical properties,complex coal structure during horizontal drilling,single completion&stimulation technology and so on,a completion technology with composite tubular string for coalbed methane(CBM)horizontal well is proposed.Completion tools,inner operation tubing and outer completion string are designed.The outer completion string is composed of casing and screen pipe.The mechanics and hydraulics calculation model of dual tubular string are optimized.A field test of this completion technology had been accomplished in No.15 coal seam in Yangquan,Shanxi Province,China.A dual tubular string of 659.5 m was run into the depth of 1591 m,and the horizonal well section in coal seam is divided into four sections by external casing packers(ECP).The tests of dual tubular string running,hydraulic circulation removing dual tubular string blocking and sticking,well washing,ECP expansion sealing and segmental completion in coal seam were accomplished.Based on the engineering data of this well,the force of dual tubular string was calculated by finite difference method,and the related hydraulic calculation was carried out.The results show that the inner tubing increases the lateral force of completion string,and the friction resistance on downhole tubular string increases by 5642.75 N.The pressure of completion tubular string is mainly affected by hydraulic loss of inner tubing and nozzles.The recommended displacement of hydraulic circulation is 16~20 L/s to remove rock and cuttings and maintain wellbore stability during completion string running.The displacement is increased to 20~24 L/s to eliminate the damage of drilling fluid to shaft wall during well washing operation.The research and field test verified the feasibility and innovation of the completion technology with composite tubular string for horizontal well,which provides a reliable basis for horizontal well diversified and adaptive stimulation in coal reservoir with complicated structure.