Time-Dependent Stresses From Fluid Extraction and Diffusion With Applications to Induced Seismicity

Abstract

Over recent decades, it has become clear that the extraction of fluids from underground reservoirs can be linked to seismicity and aseismic deformation around producing fields. Using a simple model with uniform fluid extraction from a reservoir, Segall (1989, “Earthquakes Triggered by Fluid Extraction,” Geology, 17(10), pp. 942–946) illustrated how poroelastic stresses resulting from fluid withdrawal may be consistent with earthquake focal mechanisms surrounding some producing fields. Since these stress fields depend on the spatial gradient of the change in pore fluid content within the reservoir, both quantitative and qualitative predictions of the stress changes surrounding a reservoir may be considerably affected by assumptions in the geometry and hydraulic properties of the producing zone. Here, we expand upon the work of Segall (1989, “Earthquakes Triggered by Fluid Extraction,” Geology, 17, pp. 942–946 and 1985, “Stress and Subsidence Resulting From Subsurface Fluid Withdrawal in the Epicentral Region of the 1983 Coalinga Earthquake,” J. Geophys. Res. Solid Earth, 90, pp. 6801–6816) to provide a quantitative analysis of the surrounding stresses resulting from fluid extraction and diffusion in a horizontal reservoir. In particular, when considering the diffusion of fluids, the spatial pattern and magnitude of imposed stresses is controlled by the ratio between the volumetric rate of fluid extraction and the reservoir diffusivity. Moreover, the effective reservoir length expands over time along with the diffusion front, predicting a time-dependent rotation of the induced principal stresses from relative tension to compression along the ends of the producing zone. This reversal in perturbed principal stress directions may manifest as a rotation in earthquake focal mechanisms or varied sensitivity to poroelastic triggering, depending upon the criticality of the pre-existing stress state and fault orientations, which may explain inferred rotations in principal stress directions associated with some induced seismicity.

Induced Seismicity by Groundwater Extraction at the Dead Sea Fault, Jordan

“…Although fluid extraction decreases pore pressure and increases effective pressure and thereby strengthen the rocks, mechanical coupling in heterogeneous cross‐sections may enhance seismicity. As shown by Segall (1989) and later expanded by Lambert and Tsai (2020), fluid extraction results with stress fields that is consistent with reverse faulting above and below the pumped layer and normal faulting along the reservoir boundaries. González et al.…”

Monitoring natural gas storage using Synthetic Aperture Radar: are the residuals informative?

“…There are volume decreases to the north, south, and west of the gas storage site that might be due to stress transfer from the area of injection. That is, the stress changes due to volume increases and fracture aperture changes in an elastic or poroelastic medium can induce complicated stress changes in the surrounding region (Segall 1989, Lambert and Tsai 2020, Kettlety et al 2020) that can produce associated volume changes. These effects have been observed in experiments involving fluid withdrawal from a sub-horizontal fracture zone, in both estimated fracture volume change and in borehole pressure measurements (Karasaki et al 2000, Vasco et al 2001.…”