The International Information Center for Geotechnical Engineers

Thursday, 13 December 2018 01:00

Water storage after fracking related to seismic hazard

The hydraulic fracturing water cycle: USGS The hydraulic fracturing water cycle: USGS.

New study shows that the storage of water produced from oil and gas exploitation using hydraulic fracturing is correlated with earthquake hazard.

Petroleum industry produces about 10 times more water than oil. The storage of this water is connected with increased seismicity, according to researchers from the University of Texas at Austin.

In conventional oil and gas exploitation, the water is injected back into the reservoir. However, during hydraulic fracturing, a method used to extract oil in tight reservoirs, water produced cannot be stored back due to low porosity of the rock. Therefore, the water is injected in the nearby softer geologic formations.

The study shows that the risk of seismic incidents increases due to increased pore pressure that the water storage provokes. Scientists focused on regions where water was stored after oil exploitation and recorded a rise in seismic activity. A crucial parameter, except for the quantity of water, is the location of the storage inside the ground.

For example, in Oklahoma, a region with increased activity, the water was stored in deep formations that were connected with active faults and triggered earthquakes due to the stresses induced. Recently, water injection rates dropped in an attempt to reduce seismicity. The research confirms a 70% reduction in the earthquakes occurred on 2017 (over than M 3.0) compared with such incidents in 2015. 

"Everything they (the Oklahoma Corporation Commission) did is supported by what we have in this article. The decisions they made, the directives that they put out, are supported by statistical associations we found." said Kyle Murray, adjunct professor at the University of Oklahoma and co-author of the study.

Despite this direct correlation that exists in Oklahoma, authors emphasize that the problem is more complicated. For example, Bridget Scanlon, senior research scientist at UT's Bureau of Economic Geology and lead author, states that water storage may lower the potential earthquake risk in shallow formations. In this case, the problem would be the contamination of the overlying aquifers.

Read 218 times Last modified on Thursday, 13 December 2018 15:25

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