油基钻井完井液侵入对页岩储层应力敏感性的影响  

Impacts of oil-based drilling/completion fluids invasion on the stress sensitivity of shale reservoirs

作　　者：康毅力[1] 林冲[1] 游利军[1] 王巧智[1,2] 陈强[1] 

机构地区：[1]"油气藏地质及开发工程"国家重点实验室.西南石油大学 [2]中海油能源发展股份有限公司工程技术分公司钻采工程研究所

出　　处：《天然气工业》2015年第6期64-69,共6页Natural Gas Industry

基　　金：国家科技重大专项(2011ZX05005-006-008HZ);国家科技重大专项(2011ZX05018-005-003)

摘　　要：页岩气藏水平井钻井完井过程中,油基钻井完井液易沿裂缝侵入储层,滤液对裂缝壁面的浸泡、固相颗粒堵塞微裂缝必然影响页岩储层应力敏感行为。为此,选用四川盆地志留系龙马溪组页岩作为实验岩样,开展了流体浸泡人工缝页岩岩样的应力敏感性实验,并对比了不同流体浸泡后的页岩应力敏感性差异。结果表明,白油、pH值为12的碱液、油基钻井完井液滤液浸泡后的岩样,平均应力敏感性系数较干岩样分别增大8%、26%、15%,应力敏感程度增强;高pH值油基钻井完井液对页岩的侵蚀作用弱化了页岩基块力学性质,溶蚀缝面微凸体,使页岩结构变得疏松,进一步促使裂缝产生、扩展并诱发微粒释放和微粒运移,导致页岩裂缝在外力作用下更易变形,从而强化页岩应力敏感性。该研究成果可为页岩气藏钻完井过程中的储层保护工作液选择及设计提供基础参数。During the drilling and completion of horizontal wells in shale gas reservoirs, oil-based drilling/completion fluids are liable to invade into formations along the fractures. Soaking of fracture surfaces by filtrates and plugging of micro fractures by solids may inevitably have negative impacts on the behaviors of shale reservoir stress sensitivity. Taking the Silurian Longmaxi Formation shale in the Sichuan Basin as samples, stress sensitivity experiments were carried out on samples soaked in different fluids to evaluate and compare their stress sensitivities. Research results show that average stress sensitivity coefficients of white oil soaked samples, lye soaked samples with pH value of 12 and oil-based drilling/completion fluids soaked samples are 8 %, 26% and 15 % higher than that of dry samples respectively. Moreover, stress sensitivities were all increased. Oil-based drilling/completion fluids with higher pH have erosive effects on shale formations by weakening their mechanical properties. In addition, dissolution of asperity of fracture surfaces may generate loose structures in shale and further promote the generation of fractures, expand and induce releasing and migra tion of micro-particles. Eventually, it strengthens the stress sensitivity of shale and makes fractures in shale more prone to deformation under external forces. The research results may provide basic parameters for the design and optimization of reservoir protection work fluids in shale gas drilling and completion.

关 键 词：页岩 油基钻井完井液 储层损害 应力敏感性 碱液 高PH值 

分 类 号：TE254[石油与天然气工程—油气井工程]