Role of Deep Fluid Injection in Induced Seismicity in theDelaware Basin, West Texas and Southeast New Mexico
特拉华盆地的地震活动率从2017年的每年10次本地震级（ML）3.0及以上增加到2022年的超过185次，这一增长与油气生产和废水回注到生产层位浅层或深层地层的活动相吻合。迄今为止，最大震级达到ML 5.4的地震事件发生在延伸到接收了超过四十亿桶注入的基底以上的地层中的断层上。
在这里，我们展示了该区域注入地质学、孔隙压力演化、断层稳定性和诱发地震之间的联系。我们发现，注入目标主要是具有低（<5体积%）基质孔隙度和由裂缝增强渗透性的白云岩化平台碳酸盐岩，这些岩石在流动属性上具有固有的非均质性。我们使用一个全面的三维地质模型，该模型填充了储层属性，用于流体流动模拟，并通过动态注入数据进行全局校准。从1983年到2023年，深层注入的孔隙压力变化高达5 MPa，局部增加了原生孔隙压力状态的10%。模拟结果表明，发生在深层注入附近30公里范围内的地震经历了小幅度（<0.1 MPa）的孔隙压力增加，表明这些断层对有效应力变化高度敏感，并且比通常假定的0.6具有更低的摩擦稳定性。这些结果在理解美国最活跃、地质最复杂的盆地之一中诱发地震的应力变化方面起到了关键作用。
CMG软件应用情况：
在这项研究中，CMG-STARS软件包被用来评估孔隙压力历史。流动模型有20层，从宾夕法尼亚系到前寒武纪基底，受到地层解释的约束。模型角落点网格是270×220平方公里，有123×116×20个单元，大约是1.6×1.6平方公里，包括285,360个活跃单元。平均单元厚度为103米，85%的单元厚度在24到183米之间。网格单元在南北方向上对齐。流体属性如粘度和密度被计算为温度、压力和盐度的函数。CMG-STARS软件用于模拟与深层注入相关的孔隙压力变化，并分析其对地震活动的影响。
Abstract
Rates of seismicity in the Delaware Basin of Texas and New Mexico increased from 10earthquakes per year of local magnitude (ML) 3.0 and above in 2017 to more than 185 in 2022, coincident within creasing oil and gas production and wastewater re‐injection into strata shallow or deeper than producing intervals. Events of large magnitude—up to ML 5.4 to‐date—occur on faults extending into formations above the basement that have received more than four billion barrels of injection. Here, we demonstrate the link
between injection geology, pore pressure evolution, fault stability, and induced seismicity in this region. We find that the injection targets are largely dolomitized platform carbonates with low (<5 vol.%) matrix porosity and fracture‐enhanced permeability with inherent heterogeneity in flow properties. A comprehensive, three‐dimensional geological model populated with reservoir properties is used for fluid flow modeling, with global calibration supplemented by dynamic injectivity data. Pore pressure changes with deep injection are up to5 MPa from 1983 to 2023, increasing the native pore pressure state by 10% locally. Modeling results show that earthquakes occurring at distances of up to 30 km from deep injection have experienced small (<0.1 MPa) pore pressure increases, indicating that the faults hosting these earthquakes are highly sensitive to changes ineffective stress and have lower frictional stability than the 0.6 generally assumed. These results serve as a critical step in understanding the stress changes that induce earthquakes in one of the most seismically active and geologically complex basins in the US.
Plain Language Summary
Earthquakes have become more frequent in areas with historically little seismicity and are coincident in space and time with an increase in oil and gas production and the re‐injection of waste water. Larger‐magnitude earthquakes occur on deep faults and generally within the crystalline basement. They are likely caused by wastewater injection into carbonate rocks above the basement, causing changes in pressure and stress on nearby faults. Results from this modeling work show that deep fluid injection increases pressure by up to 10% near deep injection wells
作者单位：
澳大利亚埃迪斯科文大学工程学院