动态裂缝堵漏试验装置的研制与应用

Development and Application of Dynamic Fracture Plugging Test Device

由于地层压力和井筒压力的异常变化,致使应力敏感裂缝性地层裂缝形态复杂多变,钻井液漏失问题更加严重,采用传统静态裂缝堵漏试验优选的堵漏配方难以高效封堵应力敏感性漏失裂缝。为此,研制了一套动态裂缝堵漏模拟试验装置,可通过控制裂缝内的流体压力与裂缝面闭合压力差实现裂缝动态变化过程中的堵漏模拟。对裂缝启动压力、裂缝面闭合压力、裂缝出口漏失体积/漏失速率、封堵层反向承压能力、封堵层抗钻井液冲刷时间等参数进行评价,完成了阶梯加压模式和连续加压模式下的堵漏模拟试验。试验结果表明:当堵漏配方相同,但裂缝面闭合压力不同时,裂缝启动压力不同;当堵漏材料中的大尺寸颗粒和中等尺寸颗粒含量相当时,该堵漏材料在动态裂缝内易滞留、易架桥,且形成的封堵层承受井筒波动压力的能力较强。研究结果可为治理井下复杂事故提供参考。

Due to the abnormal changes in formation pressure and wellbore pressure,the fracture morphology of stress sensitive fractured formations is complex and variable,and the problem of loss of drilling fluid is even more serious;in such a case,it is difficult to efficiently plug stress sensitive loss fractures using the optimal plugging formula selected from traditional static fracture plugging test.Therefore,a set of dynamic fracture plugging simulation test device was developed,which can achieve the simulation of plugging in the dynamic change process of fracture by controlling the difference between the fluid pressure in the fracture and the closure pressure of the fracture surface.Moreover,the parameters such as fracture initiation pressure,fracture surface closure pressure,fracture outlet loss volume/rate,reverse pressure bearing capacity of plugged zone,and drilling fluid flushing resistant time of plugged zone were evaluated;and plugging simulation tests under both stepped and continuous pressurization modes were completed.The test results show that even if the plugging formula is the same,when the fracture surface closure pressure is different,the fracture initiation pressure is different;when the content of large and medium-sized particles in the plugging material is equivalent,the plugging material is prone to retention and bridging in dynamic fractures,and the formed plugged zone has a strong ability to withstand wellbore fluctuating pressure.The research results provide reference for the treatment of complex downhole accidents.