连续油管下入煤层U型井疏通水平通道可行性研究

Feasibility Study of Coiled Tubing Runs into a Coal Seam U-shaped Well to Dredge the Horizontal Channel

新型深层煤炭开采工艺是采用U型井结构建立地下气化炉生产粗煤气,是一种清洁的煤炭开采利用技术。但是粗煤气中的固相杂质容易堵塞生产井连通通道,需要进行水平通道疏通作业。为了研究连续油管从生产井下入煤层U型井疏通水平通道的可行性,建立了连续油管下入受力分析模型,给出了连续油管过弯道可行性分析方法和连续油管极限下入深度计算方法,并采用四阶Runge-Kutta法对连续油管下入受力分析模型求解。以QT系列连续油管为研究对象,分析了连续油管从生产井下入水平通道过程中的摩阻、正压力、轴向载荷等力学特性,并讨论了连续油管过弯道可行性及其极限下入深度。结果表明:连续油管下入煤层U型井-生产井时,在造斜段所受摩阻与正压力最大,在井口位置所受轴向拉力最大。为满足连续油管在煤层U型井-生产井与水平通道连接处的强度及摩阻要求,生产井在连接处的井斜角需大于65°,生产井和水平通道方位差值需大于157°。另外,外径较小、钢级较大的连续油管可通过的安全夹角范围更大。考虑连续油管在水平段的累计摩阻及屈曲自锁,25.4~50.8 mm外径连续油管的极限下入深度均满足煤层U型井从生产井下入连续油管进入50~100 m水平通道修井作业的需求。研究结果可为煤层U型井连续油管下入水平通道作业提供一定的指导。

The new deep coal mining technology adopts U-shaped well structure to establish underground gasifier to produce coalbed methane,which is a clean utilization technology for coal mining.But the connecting passage between injection well and production well is easily blocked by crude coal gas,which usually needs to be dredged.In order to study the feasibility of unblocking horizontal channel of U-shaped wells in coal seam under coiled tubing,a force analysis model of coiled tubing was established,the feasibility analysis method of coiled tubing through the bend and the calculation method of the limit depth of the coiled tubing were given,and the four-order Runge-Kutta method was used to solve the force analysis model of coiled tubing.The mechanical characteristics of QT series coiled tubing,such as friction,press force and axial load were analyzed,and the feasibility and the limit depth of coiled tubing were discussed.The results show that the friction and plus pressure of the inclined section and the axial tension of the wellhead are the biggest when the coiled tubing goes into the U-shaped well-production well in the coal seam.In order to meet the strength and frictional resistance requirements of coiled tubing at the joint of U-shaped well and horizontal passage,the angle of inclination at the joint of production well should be greater than 65°,and the difference between production well and horizontal passage should be greater than 157°.In addition,the outer diameter is smaller,the steel grade is larger coiled tubing can pass the safety angle range is larger.Considering the cumulative frictional resistance and buckling self-locking of the coiled tubing in the horizontal section,the limit entry depth of the 25.4~50.8 mm outer diameter coiled tubing can meet the need of workover in the 50~100 m horizontal channel from the production well to the coiled tubing well.The research results can provide some guidance for the operation of run coiled tubing in horizontal channel of coal seam U-shaped well.