多因素耦合作用下致密油储层层理缝差异发育机理

Differential development of the bedding fracture is an important factor for the tight oil heterogeneous distribution and single well productivity. Insight into the differential development mechanism of the bedding fracture under multi-factor coupling is extremely significant to perfect the tight oil theory and guide the exploration and development of tight oil; however, these studies are in an initial stage. The present project focuses on the Yanchang Formation of Huaqing area in Ordos Basin, carries out methods of geostatistical analysis, experimental tests, physical and numerical modeling, and coupling analysis to study the bedding fracture in tight oil reservoirs. The bedding fracture will be accurately identitied from multi-scale based on the core, thin section and scanning electron microscope. The bedding fracture identification standard system will be built based on the core electricity correction marked by imaging logs. According to this standard system, parameters of the bedding fracture will be quantitative calculated. Based on the observation of core and thin section, experiments and numerical modeling, key factors for the development and distribution of the bedding fracture in tight oil reservoirs will be determined. The multi-factor coupling analysis and its controlling on the bedding fracture will be studied, combined with the bedding fracture critical strength under different conditions, the differential development mechanism of the bedding fracture in tight oil reservoirs will be revealed. The present study will help perfecting the tight oil theory, and provide geological basis for the exploration and development of tight oil in China.

储层层理缝差异发育是造成致密油非均质分布和影响单井产能的重要因素，多因素耦合作用下揭示其差异发育机理，对完善致密油理论以及指导致密油勘探开发均至关重要，但目前国内外对该方面的研究尚处于定性描述阶段。本项目以鄂尔多斯盆地华庆地区延长组为剖析对象，采用地质统计分析、实验测试、物理模拟、数值模拟以及耦合分析相结合的方法对致密油储层层理缝开展研究。基于岩芯、薄片以及扫描电镜的精细解剖，经岩电校正后结合成像测井的刻度，构建致密油储层层理缝识别标准体系，并在此基础上量化表征其特征参数；基于岩芯描述、薄片观测、实验测试和数值模拟，系统查明致密油储层层理缝形成和发育的控制因素；构建层理缝多控因的时空耦合关系模型，查明其对致密油储层层理缝的控制效应，在物理模拟确定不同条件下层理缝形成临界强度的基础上，揭示致密油储层层理缝差异发育机理。研究成果将深化完善致密油理论，并为我国致密油勘探开发提供地质依据。

天然裂缝是油气重要的储集空间和渗流通道，对致密砂岩储层尤为重要。层理缝发育区往往成为致密油勘探开发甜点区，储层层理缝差异发育是造成致密油非均质分布和影响单井产能的重要因素。项目以鄂尔多斯盆地华庆地区延长组为剖析对象，综合采用地质统计分析、实验测试、物理模拟、数值模拟以及理论分析等方法对致密油储层层理缝开展研究，主要取得如下成果：（1）查明了致密油储层层理缝的发育特征，其多表现为近水平或低角度发育，裂缝开度较小，基本未被充填，横向上断续分布、延伸不远，垂向上彼此独立、基本无联系，其发育分布具强非均质性，可被构造裂缝切割，岩芯中发育的层理缝多存在油浸或油迹显示；（2）量化表征并分析了延长组致密油储层现今地应力状态，地应力方向主要在NNE-SSW~ENE-WSW范围内变化，水平最大主应力（SHmax）、水平最小主应力（Shmin）和垂向主应力（Sv）数值之间遵循Sv≥SHmax>Shmin关系，呈现正断型应力机制；（3）利用多条致密油储层层理缝响应敏感的常规测井曲线，重构并获取层理缝指数曲线，建立了致密油储层层理缝识别方法体系，分析了现今地应力状态、层理缝优势方位、层理缝开度、层理缝密度以及层理缝连通性等因素对致密油储层层理缝有效性的影响，提出了判别层理缝有效性的评价方法体系；（4）探讨了鄂尔多斯盆地致密油储层层理缝成因模式，认为致密砂岩储层层理缝的形成与分布受控于“应力+压力+其它（如溶蚀作用等）”模式，是多种因素共同作用的结果，揭示了致密油储层层理缝地质意义。