丁山地区页岩储层裂缝分布预测及页岩气保存条件评价

Prediction of Fracture Distribution in Shale Reservoirs in the Dingshan Area and Evaluation of Shale Gas Preservation Conditions

针对丁山地区龙马溪组裂缝发育分布及页岩气保存条件影响认识不清的问题,通过三轴岩石力学实验,对研究区进行古构造应力场模拟,并通过莫尔-库伦准则计算岩体破裂系数,对研究区裂缝分布规律进行预测,并优选页岩气勘探目标有利区。结果表明:差应力较小的区域以及二级或三级裂缝发育区为页岩气储层裂缝优势发育区,具有良好的保存效果;在裂缝分布预测结果的基础上,根据优选的12个评价参数建立丁山地区保存评价体系和评价标准,通过权重法和叠加法将研究区划分为2类有利区,且均具有构造部位平缓、埋深大、差应力小、远离大断裂、压力系数大、裂缝发育规模小、倾角小、发育期次早等特点。研究结果可为下一步页岩气勘探和保存条件评价提供重要参考价值。

In response to the poor understanding of the fracture development and distribution and the influence of shale gas preservation conditions in Longmaxi Formation,Dingshan Area,the paleotectonic stress field in the study area was simulated through triaxial rock mechanics experiments,rock fracture coefficient was calculated by the Mohr-Coulomb criterion of rock failure,the fracture distribution pattern in the study area was predicted,and the favorable target area of shale gas exploration was optimized.The results showed that the areas with low differential stress and the areas developed with secondary or tertiary fractures were the dominant development areas for fracture development in the shale gas reservoirs,with good preservation effect.Based on the prediction results of fracture distribution,a preservation evaluation system and evaluation standards for Dingshan Area were established with the 12 selected evaluation parameters,and the study area was classified into two types of favorable areas by the weighting method and superposition method,and all of them have the characteristics of gentle tectonic positions,deep burial depth,low differential stress,far distance from large fractures,high pressure coefficient,small scale of fracture development,small dip angle,and early development period.The results of the study provide important reference for subsequent shale gas exploration and preservation condition evaluation.