石油钻采工艺2016，Vol.38Issue(5)：545-552,8.DOI:10.13639/j.odpt.2016.05.001
焦石坝页岩气储层水平井井壁失稳机理
Mechanisms of sidewall stability loss in horizontal wells drilled for shale gas development in Jiaoshiba Block
摘要
Abstract
With beddings well developed, shale gas reservoirs in Jiaoshiba Block are characterized by high strength anisotrophy, so loss of sidewall stability is frequent in these reservoirs. Therefore, direct shearing and triaxial tests were performed on core samples taken from the Longmaxi Formation to develop a new way to characterize shale strength anisotropy based on single-group weak-plane strength theory. By combining the shale strength anisotropy characterization method and model of stress distribution on sidewall, a calculation method of sidewall collapsing pressure in shale formations has been worked out. Finally, calculation and analysis have been done with Well JY1HF as an example. The calculation results show that, with large amounts of weak bedding, shale in the Longmaxi Formation shows apparent anisotropy, and shearing slippage along weak bedding is the main mechanism of sidewall stability loss. Strength of the shale soaked in drilling fluid turns weaker, but such strength reduction is not significant; collapsing pressure calcualted by using conven-tional models decreases with the increase of deviation angle, whereas collapsing pressure calculated by using the model proposed in this paper increases first and decreases later with the increase of deviation angle, and the calculation results match well with field observation results; shearing slippage of weak bedding in shale is the key of sidewall collapsing in building-up intervals, while reduction in rock strength is not the controlling factor. The research results may provide references and guidelines for drilling design, trajectory optimiza-tion of shale gas wells in Jiaoshiba Block and other regions.关键词
页岩气/井壁稳定/坍塌压力/各向异性/层理面/焦石坝区块Key words
shale gas/sidewall stability/collapsing pressure/anisotropy/bedding plane/Jiaoshiba Block分类
能源科技引用本文复制引用
崔云海,刘厚彬,杨海平,马天寿..焦石坝页岩气储层水平井井壁失稳机理[J].石油钻采工艺,2016,38(5):545-552,8.基金项目
国家自然科学青年基金资助项目“泥页岩黏土矿物表面电化学反应及岩体膨胀数值模拟研究”（编号51204142）；国家重点基础研究发展计划（973）项目“页岩气水平井钻完井关键基础研究”（编号2013CB228003）。 （）
