页岩油致密储层一体化压裂裂缝穿层扩展特征

Fractures cross-layer propagation characteristics of integrated fracturing in shale oil tight reservoir

崔壮,侯冰,付世豪,吕嘉昕

中国石油大学（北京）油气资源与探测国家重点实验室，北京 102249 中国石油大学（北京）石油工程教育部重点实验室，北京 102249

State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China MOE Key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249, China

准噶尔盆地吉木萨尔凹陷纵向上连续发育多套致密砂泥岩产层组，采用穿层压裂技术改造时，对水力裂缝垂向扩展规律认识不清，因此，文中基于水力裂缝三维穿层扩展模型，研究了应力差和岩性界面强度对水力裂缝扩展的影响。结果表明：根据水力裂缝与岩性界面作用方式的不同，裂缝呈钝化缝、T形缝、鱼骨缝和穿层缝等4种扩展形态；当垂向应力差异系数为0.2~0.5、层间最小水平主应力差异系数小于0.12时，水力裂缝易沟通岩性界面，垂向应力差异系数越小，裂缝越易穿透岩性界面扩展至相邻层位；随着无因次岩性界面强度增加，水力裂缝沿岩性界面转向减少，当无因次岩性界面强度在0.15~0.25时，是否会形成鱼骨缝或穿层缝，由垂向应力差异系数决定，而与水平最小主应力差异系数无关。根据研究成果优选压裂层位，可实现多岩性叠置页岩油层系增产改造的目标。

In the Jimsar Sag of Junggar Basin, multiple sets of tight sand and mudstone production groups have been continuously developed longitudinally, and the vertical expansion of hydraulic fractures is unknown when the cross-layer fracturing technology is used. Based on the three-dimensional cross-layer propagation model of hydraulic fractures, this paper studies the effects of stress difference and lithological interface strength on fracture propagation. The results show that according to the different modes of action between hydraulic fractures and lithological interfaces, the fractures show four expansion patterns: passivation fractures, T-shaped fractures, fishbone fractures and panetrated fractures. When the difference coefficient of vertical stress is between 0.2 to 0.5 and the difference coefficient of minimum horizontal principal stress between layers is less than 0.12, the hydraulic fracture is easy to communicate with the lithologic interface. The smaller the difference coefficient of stress between layers is, the more easily the fracture can penetrate the lithologic interface and extend to the adjacent horizon. As the strength of the dimensionless interface increases, the diversion of hydraulic fractures along the lithological interface decreases. When the lithologic interface strength is between 0.15 to 0.25, the difference coefficient of vertical stress determines whether fishbone fractures or penetrated fractures are formed, but has nothing to do with the difference coefficient of minimum horizontal principal stress. Optimizing the fracturing zone according to this will achieve the goal of stimulation and improvement of multi-lithology superimposed shale oil formations.

10.6056/dkyqt202201019