基于三维扫描技术的页岩暂堵压裂物理模拟实验

Physical simulation experiment on shale temporary plugging and fracturing based on 3D scanning technology

杨恒林,吕嘉昕,谭鹏,付卫能,饶加富

中国石油集团工程技术研究院有限公司，北京 102206 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

页岩水力裂缝扩展形态及表征方法是评价暂堵压裂效果的基础，常规裂缝形态监测手段（如示踪剂法、声发射法）难以准确反映水力裂缝的起裂与扩展规律。因此，文中结合三维扫描技术，开展真三轴暂堵压裂物理模拟实验，研究不同排量下页岩暂堵压裂水力裂缝的起裂与扩展规律；通过获取裂缝体积与面积等参数，定量表征页岩暂堵压裂的裂缝网络复杂程度，从而评价压裂改造效果。结果表明，暂堵剂可有效促进页岩水力裂缝转向、分叉，以及多裂缝的形成，水力裂缝面曲率变化反映不同注液阶段暂堵剂的累积作用效果。不同排量下，页岩暂堵压裂的裂缝形态和裂缝网络复杂程度不同：小排量条件下，暂堵剂封堵初次裂缝，形成平行于初次裂缝的简单缝；大排量条件下，暂堵剂封堵初次裂缝，形成平行于初次裂缝并伴随天然裂缝张开的复杂缝。现场可通过增大排量提高暂堵剂在裂缝中的运移距离和封堵程度，增加远端天然裂缝的激活概率。

The hydraulic fracture propagation shape and characterization method for shale are the basis for evaluating the effect of temporary plugging and fracturing. Conventional fracture shape monitoring methods such as tracer method and acoustic emission method cannot accurately reflect the law of hydraulic fracture initiation and propagation. In view of this, combined 3D fracture scanning technology, true triaxial hydraulic fracturing physical simulation experiment were carried out to study the initiation and propagation of temporary plugging and fracturing hydraulic fractures of shale under different displacements. Fracture area and volume parameters were used to quantitatively evaluate the complexity of shale temporary plugging and fracturing fractures and the effect of temporary plugging and fracturing. It is shown that the temporary plugging agent can effectively promote the shale hydraulic fracture turning, bifurcation and the formation of multiple fractures. The curvature of the hydraulic fracture surface reflects the cumulative effect of the temporary plugging agent at different injection stages. Different displacements had different effect on morphology of shale temporary plugging and fracturing fracture and the complexity of the fracture network. Under the condition of small displacement, the temporary plugging agent plugs the first fracture, forming a simple fracture that opens parallel to the first fracture. Under the condition of large displacement, the temporary plugging agent plugs the first fracture, forming a complex fracture that opens parallel to the first fracture and is accompanied by the opening of natural fractures. In the oilfield, the migration distance and blocking degree of the temporary plugging agent in the cracks can be increased by increasing the displacement, and the activation probability of the remote natural cracks can be increased.

10.6056/dkyqt202201020