古生界海相页岩储层井壁稳定影响因素分析

Paleozoic Marine Shale Reservoir Wellbore Stability Influence Factors Analysis

古生界海相页岩主要发育有水井沱组、鲁家坪组、牛蹄塘组以及五峰-龙马溪组等页岩储层。由于不同储层矿物成份、地质特征以及岩石力学特征不同,因而,会对井壁稳定产生不同的影响作用。通过对古生界海相页岩储层进行矿物成份、水化作用、岩石力学实验以及数值模拟,分析影响古生界海相页岩储层井壁稳定的因素,结果表明：①古生界海相页岩储层均不含易水化膨胀的蒙脱石;②古生界海相页岩储层具有非水敏性特征,水化作用不是影响井壁稳定的主要因素;③水基钻井液会降低古生界海相页岩储层岩石强度,降低幅度在6.4%-37.33%之间;④大倾角、层理弱面对井壁稳定有显著影响,会导致钻井液安全密度窗口会大幅减小。

The Paleozoic marine shale mainly developed Shuijingtuo group, Lujiaping group, Niutitang group and Wufeng-Longmaxi group. Because of its different mineral compositions, geological characteristics and rock me- chanical characteristics, the influence to wellbore stability is difference. Paleozoic marine shale reservoir wellbore stability influence factors were analyzed through mineral composition, water sensitivity, rock mechanics experiments and numerical simulation. Result shows：① Paleozoic marine shale reservoir without montmorillonite which easily hydration expansion; ② Paleozoic marine shale reservoir with non-water sensitivity, and hydration is not the main influence factor to wellbore stability; ③ Water-based drilling fluid decreased Paleozoic marine shale reservoir rock strength 6.4% to 37.33% ; ④ Highly steep angle and weak plane have a strong influence on wellbore stability, which can decrease range of drilling fluid density.