基于三维重构技术的裂缝扩展规律研究

Study on propagation law of fractures based on 3D reconstruction technique

水力压裂裂纹的起裂、贯通、扩展行为与地层应力状态、储集层岩石的岩性、颗粒结构等多重因素有关,因此常规均质模型无法准确地反映岩石参数及其裂缝扩展规律。而基于真实油藏砂岩,利用切片实验、电镜扫描探针实验、CT扫描实验等,获取准确的岩石矿物颗粒物理力学性质和孔隙(裂隙)结构信息,并通过模拟退火法进行了岩石模型的三维重构,针对数字岩心,开展了均质和非均质两种不同数值模型下的水力压裂裂缝扩展数值模拟研究。研究表明:对模型裂缝的扩展起主要作用的是颗粒以及裂隙;水平应力差越小,裂缝起裂压力越高,裂缝扩展长度越小;通过模三维重构技术建立非均质模型的结果更有参考价值。该方法对于水力压裂裂缝扩展机理的深入精确研究具有一定的指导意义。

The behaviors of initiation, penetrating and propagation of fractures in hydraulic fracturing is related to mul- tiple factors of the formation stress state, the lithology of reservoir rock, the grain structure, and so on. Therefore, the rock parameters and the crack propagation law can not be reflected by the conventional homogeneous model. Based on actual reservoir sandstone rocks, using CT scanning, slicing experiments, electron microscopy scanning and x -ray diffraction with probe experiments, it was obtained the accurate physical and mechanical properties of rock mineral particles and the struc- ture information of fractures or pores. And then the 3 D reconstruction of the rock model is built by simulated annealing al- gorithm. Aiming at digital cores, it was carried out study on numerical simulation of fracture propagation based on homoge- neous and heterogeneous models. The results showed that the particle and crack played a major role in fracture propaga- tion. The smaller the horizontal stress difference is, the higher the fracturing pressure is, and the smaller the fracture length is. The heterogeneous model built by the 3 D reconstruction technology has great reference value. This method has a certain guiding meaning in propagation mechanism of fractures in hydraulic fracturing.