The controversy around whether wastewater injection wells cause earthquakes was finally put to legal scrutiny in a recent proceeding before administrative hearing examiners (Examiners) with the Texas Railroad Commission, which regulates oil and gas production in the state. The Examiners found that an injection well owned by XTO Energy Inc. likely did not influence a series of earthquakes that occurred near the towns of Reno and Azle from late 2013 through spring of 2014. The Examiners recommended that the permits held by XTO, an ExxonMobil subsidiary, not be revoked.
The August 31 decision results from an order issued by the Commission directing XTO to show cause why its permit should not be revoked, following a study released by Southern Methodist University (SMU) researchers in April that concluded XTO’s well had contributed to several small earthquakes near towns atop the Barnett Shale. At a hearing in June, XTO presented substantial evidentiary critiques of the SMU study, including scientific research demonstrating that the earthquakes are being caused by “natural tectonic forces” in the Fort Worth Basin area that have been expressed throughout history. XTO asserted that the SMU study ignored a deep fault, from which the earthquakes are originating.
XTO also disputed the validity of the fluid pressure modeling in the SMU study because: 1) the model employed was not capable of accounting for the complex geological and hydrological features of the rock formation and fault system underlying the injection well, 2) the model domain failed to include the Precambrian crystalline basement rock in which the earthquakes originated, and 3) it failed to consider multi-phase flow. The Examiners, Marshall Enquist, an administrative law judge, and Paul Dubois, the technical examiner, agreed that the evidence presented confirms the deficiencies in the study identified by XTO.
The proposal for decision issued after the June hearing concluded that the weak temporal correlation between injection and seismic activities was “too small to imply a causal relationship without further corroborating evidence” and found there was insufficient evidence to determine that the XTO injection wells were likely to have contributed to the earthquakes, essentially rejecting the conclusions published by the authors of the study.
The Commission will hold a public meeting at which commissioners will vote to adopt the examiner’s recommendation, but a date for that meeting has not been set. XTO and the Commission have fifteen days from the issuance of the proposal for decision to file exceptions to the examiners’ recommendations, and another ten days to file replies.