多岩性储集层暂堵压裂缝高扩展特征试验研究

针对多岩性组合储集层的裂缝高度扩展问题,通过制备不同岩性的人工试样,并开展了室内压裂物理模拟试验,同时加入暂堵剂,分析不同岩性差异、射孔位置及排量下的水力压裂缝高扩展特征,创新了试样压后三维裂缝重构方法。研究表明,不同岩性组合试样下的主要缝高截止机制由岩石力学性质所决定,高杨氏模量岩层会阻挡缝高穿层。当层间力学性质差异较小时,裂缝发生转向扩展突破,缝高发生穿层;当层间力学性质差异较大时,裂缝扩展限制于同一岩层,缝高难以突破岩层界面。低排量下,缝高截止于应力区分界面,暂堵压裂后,裂高继续延伸突破高应力区;高排量下,裂缝沿最小主应力横向扩展,加入暂堵剂发生,裂缝转向形成新的裂缝。当射孔位置居上时,试样缝高倾向于向上扩展,暂堵压裂后形成新的起裂点;射孔位置居下,缝高扩展贯穿整个试样,暂堵压裂后形成相平行的新裂缝。研究结果为多岩性组合储集层现场压裂方案设计提供了室内试验指导。

Experimental Study on the Hydraulic Fracture Growth Characteristics with Temporary Plugging in Multi-lithology Reservoir

Aiming at the problem of fracture height propagation in multi-lithology combined reservoirs, artificial samples of different lithologies were prepared, and indoor fracturing physical simulation tests were carried out. At the same time, temporary plugging agents were added to analyze the differences in lithology, perforation positions and the high fracture propagation characteristics of hydraulic fracturing under the displacement, innovative three-dimensional fracture reconstruction method after sample compression. Studies have shown that the main fracture height cut-off mechanism under different lithology combination samples is determined by the rock mechanical properties, and the high Young"s modulus rock layer will block the fracture from passing through the layer. When the difference in mechanical properties between layers is small, the fractures will propagate and break through, and the fracture height will penetrate the layer; when the mechanical properties of the layers differ greatly, the crack propagation is limited to the same rock layer, and the fracture height is difficult to break through the rock layer interface. At low displacement, the fracture height ends at the stress separation interface. After the temporary plugging and fracturing, the fracture height continues to extend and break through the high-stress zone; at high displacement, the fracture expands laterally along the minimum principal stress, and temporary plugging agent is added to occur, and the fracture turns to form New cracks. When the perforation position is at the top, the fracture height of the sample tends to expand upward, and a new fracture point is formed after temporary plugging and fracturing; when the perforation position is at the bottom, the fracture height expands through the entire sample, and facies are formed after temporary plugging and fracturing. Parallel new cracks. The research results provide laboratory test guidance for the design of on-site fracturing schemes for multi-lithology combined reservoirs.