G构造深部地层井壁稳定研究

Wellbore Stability Study of G Structure

何阳子 邱康 熊振宇 李乾

HE Yangzi QIU Kang XIONG Zhenyu LI qian

中国石油化工股份有限公司上海海洋油气分公司石油工程技术研究院，上海　200120

Petroleum Engineering Institute, Shanghai Offshore Oil & Gas Company, SINOPEC, Shanghai 200120, China

在东海西湖凹陷G构造勘探开发作业过程中，花港组以下深部地层多次发生由井壁失稳引发的起下钻遇阻、井壁掉块等井下复杂情况。该文选取伊顿法计算了地层孔隙压力纵向剖面，发现异常压力主要集中在花港组以下深部地层。并根据莫尔库伦准则进行井壁稳定钻后分析，该构造地区井壁失稳的主要原因是钻井液密度低于地层坍塌压力导致的力学失稳，以及由钻井液泥浆性能引起的泥岩水化。为确保后续钻井作业安全，建议在G构造相关区块开展钻前压力预测研究，并优选油基钻井液以避免泥岩水化。

During the exploration and development of G structure in Xihu Sag in East China Sea, the deep strata below Huagang Formation has suffered from many underground complicated situations, such as stoppage of drilling and block of shaft wall caused by shaft wall instability. In this paper, the longitudinal profile of formation pore pressure is calculated by using Eaton method, and it is found that the abnormal pressure is mainly concentrated in the deep strata below Huagang Formation. According to Mohr Coulomb criterion, the main reason for borehole wall instability in this structural area is the mechanical instability caused by drilling fluid density lower than formation collapse pressure and mudstone hydration caused by drilling fluid mud properties. In order to ensure the safety of subsequent drilling operations, it is suggested to carry out pre-drilling pressure prediction research in the relevant block of Structure G, and optimize the oil-base drilling fluid to avoid mudstone hydration.

https://doi.org/10.3969/j.issn.1008-2336.2020.04.058