天然裂缝复杂程度对致密储层破裂特征的影响

The Effect of Pre-existing Fracture Complexity on Rupture Characteristics of Tight Reservoir

地层内部总存在孔隙、裂隙、层理、裂缝、断层等结构特征从而体现为地层地质非均质性,并在人工注采过程中发生不同尺度的破裂而体现为跨尺度的裂缝时空延展特征和致裂机理。以致密油为代表的非常规油气藏开采开发在我国油气产能中占比越来越大,并往往利用水力压裂储层改造技术产生人工裂缝以增强油气渗流而实现其规模经济开发;同时,这类低渗透油气藏亦是CO_(2)压裂、注入和封存的重要对象。文章基于真三轴大型物理模型水力压裂实验和工程尺度下水力压裂微地震监测结果,通过不同尺度裂缝/裂隙活动所致声发射和微地震事件的时空展布研究岩体多尺度裂缝的破裂特征。研究表明,无论是相对稳定的真三轴水力压裂,还是实际地质工程尺度下的水力压裂微,岩石原生裂缝、裂隙分布趋势和方位对裂缝扩展具有主控作用。

Pre-existing microscale fractures,cracks and pores in geological layer,which makes the rock or/and stratum heterogeneity,response the difference of rupture characteristics under artificial injection.The exploitation and development of unconventional oil and gas reservoirs represented by tight oil and gas accounts for an increasing proportion of China’s oil and gas production capacity,and artificial fractures are often produced by hydraulic fracturing to enhance oil and gas flow and achieve the scale of economic production,they also are the important target for CO_(2)injection and geological storage.Based on the true triaxial hydraulic fracturing experiment and the microseismic data in geological setting,this paper studies multiscale rupture process in sandstone through the temporal and spatial characteristics of acoustic event and the microseismic event.The results show that the pre-existing fractures in rock dominate the rupture pattern under the stable triaxial hydraulic fracturing stress and geological settings.