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我国部分含天然裂缝的混合岩性致密油储层受岩石非均质性的影响,压裂裂缝起裂与延伸规律复杂,裂缝形态认识不清,采用北美缝网压裂思路进行增产改造后产量差异较大。为此,本文采用岩性复杂、天然裂缝发育的大港油田沧东孔二段致密油储层井下岩样,进行三轴力学测试、矿物组分测试和CT扫描,对储层岩样的力学参数、矿物组分和天然裂缝展布情况进行了分析,选取其中含有水平、低角度、高角度和复杂天然裂缝的井下岩样进行真三轴压裂实验,并采用CT扫描对压裂裂缝进行监测,以研究含天然裂缝的混合岩性致密油储层压裂裂缝起裂与扩展规律。实验结果表明:(1)根据对压裂效果的有利程度,可将压后裂缝形态分为以下3类:水力单缝、沿天然裂缝开启和复杂裂缝;(2)天然裂缝是压后裂缝形态的主要控制因素;(3)实验中,水力裂缝遭遇天然裂缝时出现3种延伸模式:沿天然裂缝张开、穿过天然裂缝(直接穿过、转向后穿过)、被天然裂缝阻断,应力差大小决定了以上3种延伸模式;(4)天然裂缝发育程度严重影响破裂压力和压裂液滤失量。实验结果对认识含天然裂缝的混合岩性致密油储层压裂裂缝形态,评价此类储层缝网压裂效果提供了依据。
The mixed lithologic tight oil reservoirs with some natural fractures in China are affected by rock heterogeneity. The fracturing initiation and propagation of fracturing fractures are complicated and the fracture morphology is not clear. The North American seam network fracturing method is adopted to increase the output after the stimulation big different. Therefore, in this paper, three-axis mechanical tests, mineral components tests and CT scanning were performed on the rock samples with complicated lithology and well-developed fractures in the tight oil reservoir of the second member of Cangdong Kou in Dagang Oilfield. The mechanical parameters , Mineral components and distribution of natural fractures were analyzed. The downhole rock samples containing horizontal, low-angle, high-angle and complex natural fractures were selected for true triaxial fracturing tests, and CT fractures were monitored by CT scanning To study the initiation and propagation of fracturing cracks in mixed lithologic tight oil reservoirs with natural fractures. The experimental results show that: (1) According to the favorable effect of fracturing effect, the fractured fractures can be divided into the following three categories: hydraulic single seam, open along natural fractures and complex fractures; (2) Natural fractures are post-pressure fractures (3) In the experiment, there are 3 kinds of extension modes when hydraulic fractures encounter natural fractures: they spread along natural fractures, pass natural fractures (pass directly and turn behind), and are blocked by natural fractures. The stress difference determines the above three kinds of extension mode; (4) The degree of natural fracture seriously affects the fracture pressure and fluid loss of fracturing fluid. The experimental results provide a basis for understanding fracturing fractures of mixed lithologic tight oil reservoirs with natural fractures and evaluating fracturing effects of such fractures.