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Role of Preexisting Rock Discontinuities in Fracturing Fluid Leakoff and Flowback
Transport in Porous Media ( IF 2.7 ) Pub Date : 2020-09-12 , DOI: 10.1007/s11242-020-01472-3
Anna Ipatova , Dimitry Chuprakov

During hydraulic fracturing, thousands of barrels of fluid are injected into the rock surrounding the created fractures. Observations show that later during flowback, only a small fraction of the injected fluid volume is produced back. In tight naturally fractured formations, this can be explained by the leading role of preexisting rock discontinuities in the transport of fluids in such rocks. In this work, we investigate the mechanics of injected fluid flow in and out of preexisting rock discontinuities during a typical operational sequence of fracturing treatment, well shut-in and flowback. The mechanics of fluid flow in compliant discontinuities, where conductivity is sensitive to stress changes, is different from that in a stiff rock matrix. To understand and quantify rock pressurization, fluid leakoff and flowback rates, we develop a numerical model of fluid flow in a system of arbitrarily oriented discontinuities. Using this model, we predict spatial distribution of the injected fluid in a naturally fractured rock at any time after the beginning of the fracturing treatment as well as after the well shut-in and during flowback. The model explains the trapping of injected fluid in the discontinuities during production. We validate the model by comparison with field data and provide rough estimates of the volumetric fracturing fluid accumulation in the rock discontinuities after the treatment. The spatial extent of rock “flooding” around hydraulic fractures is found to depend on the density and orientation of rock discontinuities.

中文翻译:

先前存在的岩石不连续性在压裂流体渗漏和返排中的作用

在水力压裂过程中,数千桶流体被注入到形成的裂缝周围的岩石中。观察表明,在返排后期,只有一小部分注入的流体体积被生产回。在致密的天然裂缝地层中,这可以通过预先存在的岩石不连续性在此类岩石中的流体输送中的主导作用来解释。在这项工作中,我们研究了在压裂处理、关井和返排的典型操作顺序中注入流体流入和流出预先存在的岩石不连续性的力学。导电性对应力变化敏感的柔顺不连续体中的流体流动力学与刚性岩石基质中的流体流动力学不同。了解和量化岩石加压、流体泄漏和回流率,我们在任意定向的不连续系统中开发了流体流动的数值模型。使用该模型,我们可以在压裂处理开始后以及关井后和返排期间的任何时间预测天然裂缝性岩石中注入流体的空间分布。该模型解释了生产过程中注入流体在不连续性中的捕获。我们通过与现场数据进行比较来验证模型,并粗略估计了处理后岩石不连续性中体积压裂液的积累。发现水力裂缝周围岩石“溢流”的空间范围取决于岩石不连续性的密度和方向。我们在压裂处理开始后、关井后和返排期间的任何时间预测注入流体在天然裂缝性岩石中的空间分布。该模型解释了生产过程中注入流体在不连续性中的捕获。我们通过与现场数据进行比较来验证模型,并粗略估计了处理后岩石不连续性中体积压裂液的积累。发现水力裂缝周围岩石“溢流”的空间范围取决于岩石不连续性的密度和方向。我们在压裂处理开始后、关井后和返排期间的任何时间预测注入流体在天然裂缝性岩石中的空间分布。该模型解释了生产过程中注入流体在不连续性中的捕获。我们通过与现场数据进行比较来验证模型,并粗略估计了处理后岩石不连续性中体积压裂液的积累。发现水力裂缝周围岩石“溢流”的空间范围取决于岩石不连续性的密度和方向。我们通过与现场数据进行比较来验证模型,并粗略估计了处理后岩石不连续处的体积压裂液聚集。发现水力裂缝周围岩石“溢流”的空间范围取决于岩石不连续性的密度和方向。我们通过与现场数据进行比较来验证模型,并粗略估计了处理后岩石不连续性中体积压裂液的积累。发现水力裂缝周围岩石“溢流”的空间范围取决于岩石不连续性的密度和方向。
更新日期:2020-09-12
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