薄互层水力裂缝垂向扩展控制因素试验研究

新疆油田某地区油藏的储隔层岩性组合复杂，呈现突出的薄互层产状特征，研究合、分压判断条件有利于提高压裂效率，增强储层动用程度与压后改造效果。水力裂缝在薄互层中的穿层与裂缝扩展行为受薄互层地质特征与压裂施工参数的影响。基于此，开展了薄互层物理模型压裂试验，研究界面胶结、岩层分布、岩层厚度、压裂液黏度与注液排量对薄互层中水力裂缝垂向扩展的影响分析。试验结果表明：薄互层的地层特征界面胶结与岩层分布是水力裂缝垂向扩展的主要控制因素，界面胶结强度对裂缝垂向扩展行为的影响强于岩层分布；由于弱胶结界面的存在，水力裂缝垂向扩展穿层时可发生方向偏转，抑制裂缝垂向扩展；提高压裂液黏度与注液排量有利于薄互层中水力裂缝的穿层垂向扩展。

Experimental study on controlling factors of vertical propagation of thin interbedded hydraulic fractures

The lithologic combination of the reservoir interlayers in a certain area of Xinjiang Oilfield is complex, showing prominent thin-interbedding occurrence characteristics. The study of the judgment conditions of combined and separated pressure is beneficial to improve the fracturing efficiency, enhance the production degree of the reservoir and the effect of post-pressure reconstruction. The behavior of hydraulic fracture penetration and fracture propagation in thin interbeds is affected by the geological characteristics of thin interbeds and fracturing operation parameters. Based on this, fracturing experiment on thin interbed physical model was carried out to study the influence of bedding interface cementation, rock layer distribution, rock layer thickness, fracturing fluid viscosity and injection volume on the vertical propagation of hydraulic fractures in thin interbeds. The experimental results show that the stratigraphic characteristics of thin interbeds, bedding interface cementation and rock distribution are the main controlling factors for the vertical propagation of hydraulic fractures. The influence of bedding interface cementation strength on fracture vertical propagation behavior is stronger than that of rock distribution. Due to the existence of weak cemented bedding interface, the direction of hydraulic fracture can be deflected when it propagates vertically through the bedding, which can inhibit the vertical propagation of fracture. The increase of fracturing fluid viscosity and injection volume is beneficial to the vertical propagation of hydraulic fractures in thin interbeds.