July 16, 2013 — The second quarterly ISC meeting occurred July 2, 2013 in RTH 526. It was a day-long event featuring talks and presentations, ranging from updates on project progress as well as proposed tasks for the future. Specifically, progress reports were delivered for the Blackpool (the Bowland Shale), California, and Youngstown projects.
Hydraulic Fracturing in Bowland Shale
Seismicity due to hydraulic fracturing has always been a matter of concern when developing oil and gas fields in tight formations. In 2011, two events of magnitude 2.3 and 1.5 were observed in the Blackpool area of Lancashire County in United Kingdom during vertical hydraulic fracturing operations done by Caudrilla at Preese Hall-1 well. Since this area is seismically inactive, these events resulted in shut down of all fracturing operations in the region. This study aims in co-relating the hydraulic fracturing with the seismic events observed in Blackpool region, and generating a geomechanical model using various parameters which may effect the seismic activities. The study aims in using statistical data obtained during the fracturing operation to generate a numerical co-relation, which includes magnitude of seismic event, time of events, bottom-hole pressure, injection volume, and flow back volume. The proposed model also aims to establish a temporal relationship for seismic activity prediction using the time lag between seismic events and change in bottom-hole pressure.
Seismicity in the Oil and Gas Fields: A California Case Study
Seismicity caused by fracing or water injection was recorded during case studies worldwide that has raised worries from both the scientific community and general public. The main unanswered question is whether fracing or water injection have potential to cause major earthquakes in the future, and what the future forecast will be for induced seismicity in the state of California. In this report, we demonstrate how we can differentiate tectonic seismicity from an induced one in an area where both activities are present. We have analyzed all seismic events recorded between January 1980 and June 2013. At this stage of research, our focus is on the San Joaquin Basin where many wells have been completed within the major fault zones. We correlate hydraulic fracturing jobs—after January 2011—with the recorded seismicity to find a possible relationship.
Our results show that most of hydraulic fracture jobs in this area did not cause an earthquake with magnitude of 1.7 or above. We have also shown that b-value analysis could be a useful tool to detect induced seismicity and tectonic seismicity if inherent error is eliminated with careful investigation. Induced seismicity statistics and prediction studies illustrate that oil and gas field operations probably did not cause magnitude 4 or above at the initial study area at San Joaquin basin.
An Induced Seismicity Event Case Study: Youngstown, Ohio
On 31 December 2011, a magnitude 4.0 earthquake was reported in Youngstown, Ohio, an area with no historical record of seismicity. This was the most powerful of a series of tremors believed to have been brought on by fluid injection from the nearby Northstar #1 saltwater disposal well, which had ceased operation the day before out of such concerns.
Our results thus far have led us to believe that the event of 31 December was likely induced. As such, we have taken the Youngstown event to serve as a representative of induced seismic events in classically stable continental margin environments. We have analyzed available data to gain a better understanding of the subsurface physics of induced events. We will use data from sources and our own analysis to work towards a local velocity model and local attenuation curve of magnitude propagation, as well as the development of a predictive model based upon the local geophysical data. Above all, we intend to provide a clear outline of how to apply this analysis technique to events in other locations, with an eye toward a broad, comparative investigation down the road.