层理性页岩油储层钻井过程中井壁稳定性差,易发生井壁坍塌、卡钻等事故。为揭示层理面对页岩油储层井壁坍塌扩径的影响规律,基于MG-C强度准则和多弱面准则,构建了页岩油储层钻井井周受力数值模型和坍塌区域预测方法,计算了单一弱面和多弱面在不同应力机制下的坍塌扩径规律。研究表明:多弱面的存在使基质和弱面破坏同时发生,引发井壁坍塌形态复杂化,弱面诱发的井壁坍塌扩径要显著高于基质;相较于走滑应力机制,正应力机制下井壁坍塌随应力比变化更显著,坍塌风险更高;正应力机制下,当应力比超过1.5,井壁扩径率超过100%,且急剧增大。研究成果可为在不同区域应力机制的钻井过程中,预防页岩油储层井壁垮塌提供理论指导。
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