摘要
传统的保护裂缝性储层的钻井完井液设计以裂缝的静态宽度为依据,极少关注由应力敏感性引发的裂缝动态宽度变化行为,导致暂堵材料粒径小于储层动态缝宽,无法有效控制漏失而严重损害储层。以泌阳凹陷深层典型致密砂岩储层为研究对象,基于岩心观察和测井资料获取静态缝宽,并开展应力敏感实验,研究应力变化对静态缝宽的影响;通过有限元法模拟确定应力扰动下动态缝宽变化,进而优选屏蔽暂堵钻井完井液配方。实验表明,根据动态缝宽优选的屏蔽暂堵完井液封堵时间不超过5 min,返排恢复率达80%,滤饼承压能力达15 MPa,高质量滤饼可以快速封堵裂缝,有效预防井漏发生。钻井作业过程中储层保护试验成功与失败的案例说明,强应力敏感裂缝性储层保护必须考虑动态缝宽参数,且暂堵粒子粒径上限应随着钻井完井液密度的增加而适度放大,才能覆盖最大动态缝宽范围。
Fractures existed in tight sands, although are beneficial to the development of oil and gas, they also inevitably lead to mud losses, causing severe damage to the reservoirs into which the mud loses. Temporary plugging technology has been developed to avoid such formation damage. Conventional temporary plugging technology uses the static fracture width to design particle sizes required to plug the fractures, seldom considering the change of fracture widths under pressure. Particle sizes calculated from static fracture widths are therefore less than that best fit for fracture plugging, and cannot effectively plug fractures to avoid reservoir damage. Based on core survey and static fracture width obtained from wireline logging data, the effect of stress change on static fracture width was studied, using finite element method to determine the change of fracture width with stress, and to optimize the temporary plugging drill-in fluid formulation. Laboratory experiments showed that using the optimized temporary plugging drill-in fluid, plugging time was no longer than 5 min, percent recovery of core permeability was as high as 80%, and the pressure bearing strength of mud cake was as high as 15 MPa. This high quality mud cake plugged the fractures quickly, avoiding mud losses into reservoir formations. Field drilling operation showed that, in designing reservoir protection program, dynamic fracture width should be used, and the upper size limit of the plugging particles should be properly increased with increase in mud weight, allowing plugging of the widest fractures under dynamic conditions.
出处
《钻井液与完井液》
CAS
北大核心
2014年第6期28-32,97,共5页
Drilling Fluid & Completion Fluid
基金
国家重点基础研究发展计划(973计划)(2010CB226705)
国家科技重大专项(2011ZX05018-005-003)
