涠西南流沙港组页岩储层地质特征及可压性评价

涠西南凹陷流沙港组页岩油资源丰富，但该储层地质条件复杂，储层可压性评价难度较大，亟需开展相关研究。本文综合岩心物性分析、核磁共振、扫描电镜、岩石热解、X射线衍射和力学实验等资料，分析了流沙港组页岩油储层地质特征，采用耦合脆性指数、水平应力差异系数和裂隙密度的可压性评价模型对不同类型油页岩进行可压性评价。研究表明，流沙港组页岩孔隙度主要集中在1%~5%，渗透率多小于0.1×10-3 μm2，储层表现为低孔低渗特征。孔径以微孔、介孔为主，主要集中在0.001~0.05 μm，页岩储集空间类型包括晶间孔、有机质孔、粒间孔和微裂隙4种孔隙类型。流二段泥页岩、油页岩的有机质类型分别为Ⅱ1-Ⅱ2型、Ⅰ-Ⅱ1型，普遍处于成熟阶段。储层岩石主要由长英质矿物组成，平均黏土矿物含量为33.24%。夹层型和互层型油页岩脆性较基质型和纹层型油页岩好，岩石储层各向异性较强。可压性评价结果显示：基质型和纹层型油页岩可压性指数较低，页岩油动用难度大；夹层型油页岩可压性指数为51.16%，具有一定的压裂改造潜力；互层型油页岩可压性指数最高，达到了57.03%，建议优先进行储层压裂改造。本研究对深入理解流沙港组页岩油储层地质特征和后期压裂施工具有重要意义。

Geological Characteristics and Evaluation of Fracturability of Weixinan Liushagang Formation Shale Reservoirs

Shale oil resources are rich in the Liushagang Formation of the Weixinan Depression, but the reservoir''s geological conditions are complex and evaluating its fracturability is difficult, making relevant studies urgently needed. In this paper, the geological characteristics of shale oil reservoirs in the Liushagang Formation were analyzed by combining core physical analysis, nuclear magnetic resonance, scanning electron microscope, rock pyrolysis, X-ray diffraction, and mechanical experiments. A fracturability evaluation model with coupled brittleness index, horizontal stress difference coefficient, and fracture density was used to evaluate the fracturability of different types of oil shales. The results show that the Liushagang Formation shale has low porosity (mainly in 1%~5%) and low permeability (mostly less than 0.1×10-3 μm2) and the reservoir shows the characteristics of low pore and low permeability. The pore size is mainly micropore and mediumpore, mainly concentrated in 0.001~0.05 μm. The shale reservoir space type includes four pore types: intercrystalline pore, organic matter pore, intergranular pore, and microfracture. The organic matter types of mud shale and oil shale in the second member of the Liushagang Formation are Ⅱ1-Ⅱ2 type and Ⅰ-Ⅱ1 type respectively, which are generally in the mature stage. The reservoir rocks are mainly composed of felsic minerals, with an average clay mineral content of 33.24%. The brittleness of interlayer and interbedded oil shale is preferable to that of matrix and lamina oil shale, and the rock reservoir has a stronger anisotropy. It was shown by fracturability evaluation that: the low fracturability index of matrix and lamina oil shale makes it difficult to use for shale oil; interlayer oil shale has a fracturability index of 51.16%, with some potential for fracture transformation; the fracturability index of interbedded oil shale is the highest, reaching 57.03%, making it recommended to prioritize reservoir fracture transformation. This study has great significance in the in-depth understanding of the geological characteristics of the shale oil reservoir in the Liushagang Formation and the subsequent fracturing construction.