Abstract Extensive research has been conducted over the past two decades to improve hydraulic fracturing methods used for hydrocarbon recovery from tight reservoir rocks such as shales. Our focus in this paper is on thermal fracturing of such tight rocks to enhance hydraulic fracturing efficiency. Thermal fracturing is effective in generating small fractures in the near-wellbore zone - or in the vicinity of natural or induced fractures - that may act as initiation points for larger fractures. Previous analytical and numerical results indicate that thermal fracturing in tight rock significantly enhances rock permeability, thereby enhancing hydrocarbon recovery. Here, we present a more powerful way of simulating the initiation and propagation of thermally induced fractures in tight formations using the Cohesive Zone Method (CZM). The advantages of CZM are: 1) CZM simulation is fast compared to similar models which are based on the spring-mass particle method or Discrete Element Method (DEM); 2) unlike DEM, rock material complexities such as scale-dependent failure behavior can be incorporated in a CZM simulation; 3) CZM is capable of predicting the extent of fracture propagation in rock, which is more difficult to determine in a classic finite element approach. We demonstrate that CZM delivers results for the challenging fracture propagation problem of similar accuracy to the eXtended Finite Element Method (XFEM) while reducing complexity and computational effort. Simulation results for thermal fracturing in the near-wellbore zone show the effect of stress anisotropy in fracture propagation in the direction of the maximum horizontal stress. It is shown that CZM can be used to readily obtain the extent and the pattern of induced thermal fractures.

中文翻译：

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使用粘性带法 (CZM) 进行页岩热压裂模拟

摘要 在过去的 20 年中，人们进行了广泛的研究，以改进用于从页岩等致密储层岩石中采油的水力压裂方法。我们在本文中的重点是对此类致密岩石进行热压裂，以提高水力压裂效率。热压裂可有效地在井筒附近——或在天然或诱导裂缝附近——产生小裂缝，这些裂缝可作为较大裂缝的起始点。先前的分析和数值结果表明，致密岩石中的热压裂显着提高了岩石渗透率，从而提高了油气采收率。在这里，我们提出了一种使用粘性带法 (CZM) 模拟致密地层中热致裂缝的萌生和扩展的更强大的方法。CZM 的优点是： 1) 与基于弹簧质量粒子法或离散元法 (DEM) 的类似模型相比，CZM 模拟速度快；2) 与 DEM 不同，岩石材料的复杂性，例如与尺度相关的破坏行为，可以纳入 CZM 模拟；3) CZM 能够预测岩石中裂缝扩展的程度，这在经典的有限元方法中更难确定。我们证明了 CZM 为具有挑战性的裂缝扩展问题提供了与扩展有限元方法 (XFEM) 相似精度的结果，同时降低了复杂性和计算工作量。近井区热压裂模拟结果表明，应力各向异性对裂缝沿最大水平应力方向扩展的影响。