Hydraulic fracturing becomes a key technology for unconventional oil and gas development. As a fracturing fluid, CO₂ displays considerable advantages, particularly in shale gas exploitation. However, little research has quantitatively analyzed the effectiveness and efficiency of CO₂ fracturing in naturally fractured reservoirs. In this study, a CO₂ fracturing model is established in naturally fractured reservoirs. A series of fracturing cases in single- and multiple- fracture(s) are conducted based on the simplified three-dimensional displacement-discontinuity-method. Compared to induced fractures by slickwater and gel, the results show that CO₂ fracturing can generate relatively longer but narrower fractures due to the low breakdown pressure and pressure drop in fractures. The pressure drop in the single fracture by CO₂ fracturing is respectively 60.48% and 78.88% lower than that by slickwater and gel fracturing at the same injection time. Simultaneously, in naturally fractured reservoirs, CO₂ fracturing can activate more natural fractures to connect with each other and create a larger stimulated reservoir volume. For a single fracturing, the active natural fractures volume of CO₂ fracturing is 3.7 and 9.2 times that of slickwater and gel fracturing, respectively. For multiple fracturing, the active natural fractures volume of CO₂ fracturing is 2.5 and 4.4 times that of slickwater and gel fracturing, respectively. Additionally, the sensitivity analyses in natural fracture spacing and length show that both natural fracture spacing and length can significantly determine natural fractures' distribution and connectivity. By CO₂ fracturing, a reservoir with relatively smaller natural fracture spacing and longer natural fracture length can be activated more natural fractures. The present work can help the scholars and the readers better understand the effectiveness and efficiency of CO₂ fracturing, especially in naturally fractured reservoirs.

水力压裂已成为非常规油气开发的关键技术。作为压裂液，CO _2具有相当大的优势，特别是在页岩气开采中。然而，很少有研究定量分析天然裂缝储层中CO ₂压裂的有效性和效率。在这项研究中，在自然裂缝储层中建立了一个CO ₂压裂模型。基于简化的三维位移-间断法，进行了单裂缝和多裂缝的一系列压裂案例。与滑水和凝胶诱发的裂缝相比，结果表明CO ₂由于低的破裂压力和裂缝中的压降，压裂可产生相对较长但较窄的裂缝。在同一注入时间下，CO ₂压裂产生的单个裂缝的压降分别比滑水和凝胶压裂产生的压降低60.48％和78.88％。同时，在天然裂缝的油藏中，CO ₂压裂可以激活更多的天然裂缝，使它们相互连接，并产生较大的增产油藏。对于单次压裂，CO ₂压裂的活动自然裂缝体积分别是滑水和凝胶压裂的3.7倍和9.2倍。对于多次压裂，活性天然裂缝的CO _2量压裂分别是滑水和凝胶压裂的2.5倍和4.4倍。此外，天然裂缝间距和长度的敏感性分析表明，天然裂缝间距和长度都可以显着确定天然裂缝的分布和连通性。通过CO ₂压裂，具有相对较小的天然裂缝间距和较长的天然裂缝长度的储层可以活化更多的天然裂缝。目前的工作可以帮助学者和读者更好地理解CO ₂压裂的有效性和效率，特别是在天然裂缝性油藏中。