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Numerical Simulation of Multicrack Propagation Dynamics in Supercritical CO2 Fracturing of Tight Reservoirs

Dianfa Du, Peng Liu, Jinchi Teng,Zilin Zhang,Yuan Li,Yujie Tang, Xinrui Li, Yuan Zhao

Energy & Fuels(2022)

China Univ Petr East China

Cited 1|Views7
Abstract
Supercritical carbon dioxide (SC-CO2) fracturing technology, as a promising waterless fracturing technology, plays an increasing role in the development of tight reservoirs. Based on computational fluid dynamics software, the flow state of CO2 in the reservoir was analyzed, the characteristics of CO2 were characterized, a numerical simulation method of SC-CO2 fracturing based on cohesive units was proposed, and a fluid-solid coupling numerical model of SC-CO2 multistage and multicluster fracturing was established. The dynamic interaction between fractures in the process of segmented and multicluster fracturing was studied, and the final shape of multicrack propagation was discussed. The results indicated that the interaction between cracks generated by single stage and three-cluster fracturing will keep the two main cracks away from each other, which is helpful to increase the control area of the cracks. The perforation phase angle is an important parameter to control crack morphology, and an improper perforation phase angle setting may turn new cracks into existing cracks. During two-stage and four-cluster fracturing, the directions of adjacent perforation cracks in each stage are distributed at intervals; the geometric distribution of cracks in the left and right clusters is relatively uniform, and the crack lengths generated by the two inner perforation positions in each stage are significantly greater than the crack lengths outside. The three-stage and single-cluster fracturing is conducive to the formation of a crack network, the crack length is basically linearly distributed with time, and the maximum crack width increases slightly in sequence for the three stages. The more the fractured perforations per cluster for the same wellhead injection rate, the lower the crack width. This study is expected to provide theoretical guidance for SC-CO2 multistage and multicluster fracturing in tight reservoirs.
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要点】:本文通过数值模拟研究超临界二氧化碳(SC-CO2)在致密储层水力压裂过程中的多裂缝传播动力学,提出了一种基于粘合单元的SC-CO2压裂数值模拟方法,并建立了SC-CO2多阶段和多簇压裂的流固耦合数值模型,探讨了分段和多簇压裂过程中裂缝间的动态相互作用,以及多裂缝传播的最终形态。

方法】:采用计算流体动力学软件分析储层中CO2的流动状态和特性,基于粘合单元提出SC-CO2压裂的数值模拟方法,并建立流固耦合的数值模型。

实验】:通过模拟不同阶段和簇数的压裂过程,研究了裂缝间的相互作用和裂缝形态的控制因素,发现分段和多簇压裂有助于增加裂缝控制面积,优化射孔相位角可以防止新裂缝合并到现有裂缝中,多阶段和单簇压裂有利于裂缝网络的形成,裂缝长度随时间线性分布,最大裂缝宽度在不同阶段中逐渐增大,而相同井口注入率下,簇内射孔数越多,裂缝宽度越低。研究为致密储层SC-CO2多阶段和多簇压裂提供了理论指导。