松辽盆地大情字井地区砂-页复合储层可压性评价

Fracability evaluation of sandstone-shale interbedded reservoir in Daqingzijing area,Songliao Basin

储层可压性评价是判断储层被有效改造的难易程度以及确定压裂“甜点”的有效方法。然而,目前国内外的储层可压性评价方法主要集中在单一岩性上,未考虑多岩性组合情况。选取松辽盆地大情字井地区青山口组砂-页夹层型储层为研究对象,通过对不同深度的砂岩和页岩进行X射线衍射和岩石力学实验,利用模糊层次分析法建立一种新的基于能量演化与应力-应变曲线中不同阶段脆性敏感指数的脆性评价方法。同时,对复合岩石脆性破坏程度进行分析和定量评价,将复合岩石脆性指数与矿物含量和黏聚力结合,建立多岩性复合储层的可压性评价体系。实验结果表明:复合岩样的单轴和三轴抗压强度随着页岩夹层厚度减少而降低,但脆性指数随页岩夹层厚度减少先降低后增加,可压性指数随围压增加而降低。基于连续取芯进行的力学实验和矿物含量实验,绘制可压性指数随埋深变化的曲线,将现场微地震监测结果与对应埋深储层段的可压性指数进行比较,验证了该可压性评价方法的准确性。研究结果为多岩性复合储层的压裂设计提供了关键参数和理论依据。

The evaluation of reservoir fracturability is an effective method to characterize the difficulty of reservoir effective reconstruction and to judge the“sweet spots”for fracturing.However,the current domestic and foreign evaluation methods for reservoir fracturability do not fully consider the multi-lithology combination stratification.This article takes the sand-shale interbedded reservoir of Qingshankou Formation in Daqingzi area of Songliao Basin as the research object,and carries out X-ray diffraction and mechanical experiments on sandstone and shale at different depths.A new brittleness evaluation method based on the energy evolution and different stages of brittleness sensitivity index in the stress-strain curve is established through fuzzy analytic hierarchy process.The brittleness index of composite rock is analyzed and quantitatively evaluated,and the brittleness index of composite rock is combined with mineral content and cohesive strength to establish a fracturability evaluation system for multilithology composite reservoir.Experimental evaluation results show that the uniaxial and triaxial compressive strength of composite rock samples decrease with the decrease of shale interbed thickness,but the brittleness index first decreases and then increases with the decrease of shale interbed thickness,and the fracturability index decreases with the increase of confining pressure.By conducting continuous coring,mechanical experiments and mineral content tests,the curve of fracturability index changing with burial depth is plotted,and the results of on-site microseismic monitoring are compared with the corresponding burial depth reservoir fracturability index,which validates the accuracy and feasibility of this fracturability evaluation method.The research results can provide reference for fracturing transformation of multi-lithology composite layered reservoirs.