酸蚀条件下微型钻头联合高压水射流破岩机理研究

With the increasing difficulty of oil and gas exploration, oil and gas well stimulation is the key factor of oil and gas exploration. Fishbones multilateral stimulation technology is the oil and gas well stimulation developed in recent two years, rock fragmentation is achieved efficiently by combining micro conical bit with high-pressure water jet, accompanying by the fracture acidified by acidizing fluid. Cracks will be quickly initiated and expanded inside rock with high-pressure water jet. The cracks are then acidified by acidizing fluid, thus the rock strength will be further decreased, achieving the purpose of fragmenting rock quickly and efficiently. By combining theoretical analysis with experiments, the rock mechanical characteristics with high-pressure water jet is researched and the corresponding mathematical model of rock crack propagation and damage is established. The optimal parameters of water jet are determined and the rock breaking efficiency of the fishbones multilateral stimulation technology is validated by high-pressure water jet erosion experiments. Numerical simulation of ABAQUS and TOUGHREACT is combined to simulate the physical mechanism of micro conical bit on rock and the chemical erosion mechanism of acidizing fluid on rock. The physical-chemical coupling mechanism of rock fracture propagation is investigated and validated by high-pressure water jet erosion experiments, providing a theoretical basis for rock fragmentation with high-pressure water jet under acidizing conditions.

随着油气勘探开发难度的不断增加，油气增产措施是油气勘探开发的关键环节。鱼骨刺井增产系统是近两年发展起来的新型增产措施，其碎岩是通过微型钻头联合高压水射流，同时辅以酸化液酸蚀裂缝进行高效破碎的。岩石在高压水射流条件下，内部会快速产生裂纹并扩展，酸化液刻蚀裂缝，进一步降低岩石强度，达到快速高效破碎岩石的目的。通过理论分析和实验相结合的研究手段，研究微型钻头高压水射流作用下岩石的受力特征，建立微型钻头高压水射流作用下岩石裂纹扩展、岩石损伤的数学模型；进行鱼骨刺井系统喷嘴高压水射流实验，确定最优水射流参数，验证鱼骨刺井针管的破岩高效性。运用ABAQUS和TOUGHREACT数值模拟，对微型钻头破岩的物理作用和酸化液对岩石的化学侵蚀进行联合仿真，探讨岩石裂纹扩展的物理-化学耦合作用机理，并通过高压水射流酸蚀实验验证，为酸化液辅助破岩提供理论基础。

油气勘探开发难度不断增大，提高破岩效率是油气勘探开发的关键环节。本项目针对酸蚀条件下钻头联合高压水射流辅助碎岩这一科学问题，以快速降低岩石强度、提高钻进效率为最终目的，通过理论分析、数值模拟和实验研究相结合的方法，对鱼骨刺井喷酸增产系统进行了优化设计，探讨了鱼骨刺井高压水射流作用下岩石的力学行为，构建了THMCD耦合模型系统的揭示了多场耦合作用下碳酸盐岩储层酸化压裂过程热流固、损伤演化、PH值和离子浓度的变化，探究了酸化压裂增透机理，分析了磨料射流辅助PDC齿破岩动力学特性，为钻头联合高压水射流辅助钻井提速提供了理论依据。