Revisiting the classical earthquake experiment in the Rangely oil Field, Colorado, 1970: insights from coupled flow and geomechanical modeling

Josimar Alves da Silva, Hannah Byrne, Andreas Plesch, John H. Shaw, & Ruben Juanes

Published August 8, 2019, SCEC Contribution #9376, 2019 SCEC Annual Meeting Poster #155

The earthquake experiment conducted in the Rangely oil field, Colorado, in 1970, was pioneering in elucidating the correlation between wastewater injection and induced earthquakes. This correlation, in spite of the wealth of data collected during the experiment, has been established only qualitatively. Here, we revisit the Rangely experiment using a coupled flow and geomechanical model to quantitatively investigate why and how water injection in the oil field induced earthquakes not only near the injector wells but also away from them.

We build a geological model for the Rangely oil field that includes the major faults in the area. We develop a flow reservoir model that simulates the pressure distribution in the field, and find good agreement with reported public pressure data. The pore pressure distribution is then used in a one-way coupled geomechanical model to obtain stress distribution along the faults in the field due to the water injection experiment.

We use changes in the Coulomb Failure Function (dCFF) to investigate the potential for fault failure, and find that water injection may have caused fault destabilization (dCFF > 0) as large as dCFF = 10 MPa in the strike-slip fault located near to the injector wells and producing wells, in agreement with earthquake locations reported during the experiment (a cluster of events that we refer to as ‘upper cluster’). In addition, our model reveals dCFF ~ 0.5 MPa (also indicative of fault destabilization) in a non-productive area in the strike- slip fault away from the injector wells as a result of poroelastic effects. This is roughly coincident with the location of the majority of the earthquakes reported during the experiment (which we refer to as ‘lower cluster’).

This combination of reported earthquake locations along with our modeled dCFF values provide an exceptional opportunity to make inferences on the prevalent value of the friction coefficient on slipping faults, and to make quantitative interpretations of induced vs. triggered seismicity from fluid injection in the subsurface.

Key Words
induced seismicity, geomechanics, flow, earthquakes

Citation
Alves da Silva, J., Byrne, H., Plesch, A., Shaw, J. H., & Juanes, R. (2019, 08). Revisiting the classical earthquake experiment in the Rangely oil Field, Colorado, 1970: insights from coupled flow and geomechanical modeling. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)