Published on : Jul 31, 2019
Brine is a byproduct of oil and gas production. It is in the form of toxic wastewater. Well-drillers generally dispose off the brine by injecting it in deep rock formations. These injections at times can cause earthquakes. Most of the time these quakes are small, however some of them have been quite large and have caused massive damage.
It has been difficult to predict the exact degree of seismic activity due to this brine injection. Predicting such activities involve lot of variables such as flow of brine through rocks, regional stress on geological faults, and quantity of brine injected among others.
Now a group of scientists from Department of Energy at the Arizona State University have developed a novel method to determine the seismic activity from brine disposal.
Traditional Approach was Key for Finding Solution
To find the solution, the research team, led by Guang Zhai, took a very traditional approach. The team looked at several different brine amounts that were injected in the rock formations. They also checked how it disturbed the crustal stresses and led an earthquake on a given stress fault.
The key was developing a physically sound model that could blend the ability of the rock to transport the injected wastewater and rock’s elasticity and ability to handle fluid pressure. The model collated the data from the last 23 years of wastewater injections at over 700 Oklahoma wells.
To make the model more realistic, researchers included rocks that mirrored the mechanical properties of those in Oklahoma. The result was positive that could successful predict the changes in the crustal stress due to wastewater injection.
Researchers used a well-known physical model of how the quakes begin so that they could relate the stress disturbances to the size and number of the quake.
Now with this method, well-drillers can now predict the probability of the size of an earthquake with the prior information about amount of brine injected in the rock formations.