Reasonable volumetric fracturing effect evaluation is the key to effective stimulation of fractured reservoir. Traditional fracturing effect evaluation is mainly conducted by the SRV (stimulated reservoir volume), fracture length, fracture width and other indicators, ignoring the influence of failure mode on fracturing performance. In this paper, the different fracture modes including main fractures, branch fractures and self-supporting fractures contained in the fracture network and their contributions to fracturing effect were studied in depth by numerical simulation. The results show that the main fracture formed by tensile failure has the largest width but simple shape and relatively small distribution range, while the branch fracture has a slightly smaller width but effectively expands the main fracture. Although the self-supporting fracture by shear failure is not connected, it can still improve the overall flow conductivity. The angle and number of natural fractures in fractured reservoir have a significant effect on fracture network scale and fracturing effect. When the number of natural fractures is larger, both of the number and proportion of branching fractures and self-supported fractures are larger, although the isolated self-supported fractures account for a larger proportion, the overall flow conductivity of the final fracture network is stronger. When the angle of natural fractures is larger, the natural fractures in uniform stress field are easier to be connected by hydraulic fractures and the final fracturing effect is better. The research methods and results have a certain guiding significance for the evaluation of volumetric fracturing effect in fractured reservoirs and are conducive to the reasonable selection of favorable fracturing areas and engineering parameters.

合理的体积压裂效果评价是裂缝性油藏有效改造的关键。传统压裂效果评价主要通过SRV（改造储层体积）、裂缝长度、裂缝宽度等指标进行，忽略了破坏模式对压裂效果的影响。本文通过数值模拟，深入研究了裂缝网络中包含的主裂缝、分支裂缝和自支撑裂缝等不同裂缝模式及其对压裂效果的贡献。结果表明，拉伸破坏形成的主裂缝宽度最大但形状简单，分布范围相对较小，而分支裂缝宽度略小但有效扩展了主裂缝。剪切破坏自支撑裂缝虽然没有连通，但仍能提高整体导流能力。裂缝性油藏天然裂缝的角度和条数对缝网规模和压裂效果有显着影响。当天然裂缝数量较多时，分支裂缝和自支撑裂缝的数量和比例均较大，虽然孤立的自支撑裂缝占比较大，但最终缝网的整体导流能力较强. 天然裂缝夹角越大，均匀应力场中的天然裂缝越容易被水力裂缝连通，最终压裂效果越好。