title: Gas injection may have triggered earthquakes in the Cogdell oil field, Texas.
abstract: Between 1957 and 1982, water flooding was conducted to improve petroleum production in the Cogdell oil field north of Snyder, TX, and a contemporary analysis concluded this induced earthquakes that occurred between 1975 and 1982. The National Earthquake Information Center detected no further activity between 1983 and 2005, but between 2006 and 2011 reported 18 earthquakes having magnitudes 3 and greater. To investigate these earthquakes, we analyzed data recorded by six temporary seismograph stations deployed by the USArray program, and identified 93 well-recorded earthquakes occurring between March 2009 and December 2010. Relocation with a double-difference method shows that most earthquakes occurred within several northeast-southwest-trending linear clusters, with trends corresponding to nodal planes of regional focal mechanisms, possibly indicating the presence of previously unidentified faults. We have evaluated data concerning injection and extraction of oil, water, and gas in the Cogdell field. Water injection cannot explain the 2006-2011 earthquakes, especially as net volumes (injection minus extraction) are significantly less than in the 1957-1982 period. However, since 2004 significant volumes of gases including supercritical CO2 have been injected into the Cogdell field. The timing of gas injection suggests it may have contributed to triggering the recent seismic activity. If so, this represents an instance where gas injection has triggered earthquakes having magnitudes 3 and larger. Further modeling studies may help evaluate recent assertions suggesting significant risks accompany large-scale carbon capture and storage as a strategy for managing climate change.
authors.affiliation: School of Earth Sciences and Resources, China University of Geosciences, Beijing 10083, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Gan
authors.forename: Cliff
authors.initials: C
authors.lastname: Frohlich
mesh_terms: D002245:Carbon Dioxide; D055866:Earthquakes / Q000266:history*; D019652:Extraction and Processing Industry / Q000379:methods*; D005740:Gases; D049674:History, 21st Century; D061329:Oil and Gas Fields; D013781:Texas
chemical_list: D005740:Gases; D002245:Carbon Dioxide
keywords: carbon sequestration; fluid injection; triggered seismicity