Abstract

Acidification as an effective means of reservoir modification, it is necessary to investigate the influence of acid on the mechanical properties and fracture initiation and extension of oil shale. We conducted acidification test using hydrochloric acid, and performed numerical simulation and multi-factor analysis for hydraulic fracturing. Results show that acidification greatly reduced the elastic modulus and tensile strength by 66.2% and 65.9%, and the void ratio of the oil shale increased from 0.0036 to 0.046. Meanwhile, with increasing acidification time, the fracture morphology extended from oblong to long-narrow and the initiation pressure dropped from 14.03 MPa to 9.39 MPa. We found that the tensile strength of the oil shale was the major factor affecting fracture initiation and extension. Further, an optimal acidification time existed, which was between 48 h and 96 h, wherein acid should be injected again at 48 h to improve the acidification efficiency.

摘要

酸化作为油藏改造的有效手段，有必要研究酸化对油页岩力学性质和裂缝起裂延伸的影响。进行盐酸酸化试验，对水力压裂进行数值模拟和多因素分析。结果表明，酸化使弹性模量和拉伸强度大大降低了66.2%和65.9%，油页岩孔隙率从0.0036增加到0.046。同时，随着酸化时间的增加，裂缝形态由长圆形扩展到长窄，起裂压力从14.03 MPa下降到9.39 MPa。我们发现油页岩的抗拉强度是影响裂缝起裂和延伸的主要因素。此外，存在最佳酸化时间，