June 4, 2021, Mella McEwan, firstname.lastname@example.org, Midland Reporter-Telegram
Induced seismicity – manmade earthquakes – have been rattling the Permian Basin, including 13 around the Midland area during the month of April.
While there are a number of reasons for induced seismicity, the most common is injection of produced water into wells at or near sensitive subsurface formations, said Joshua Adler, founder and chief executive officer of Sourcewater Inc.
Speaking with the Reporter-Telegram by telephone, Adler noted that in the first quarter of 2021, the number of earthquakes at 3.0 magnitude or greater in Texas is already 60 percent of all earthquakes recorded last year. He attributes that in part to increased activity this year. But also, he said, “my sense is the space in the subsurface formation where the water goes is filling up.”
That space is not infinite, he noted, and at a certain point as those sites fill up, pressure rises rapidly in order to maintain the same rate of injection.
“If you keep pushing water, that pore space will break down and cause the water to go where it shouldn’t go or where you didn’t mean for it to go. One place is the nearest fault lines.”Not only could that lubricate the lines and cause them to shift, resulting in an earthquake, but that water could also find its way into producing oil and gas reservoirs nearby, watering out the wells.
Sourcewater has built a 3D database of all known geologic fault lines in the Permian Basin – about 2,000 – mapped every 200 feet. The company has also built an analysis of the true depth of every injection well so companies proposing to drill injection wells can not only see where fault lines are but which formations are already filling up.
“If it’s a risky disposal site, shut it down, cut the rate in half or send the water to another third party or dictate which wells that third party can use,” he advised. That information can let operators make better, more-informed decisions.
Another key point from Adler is that there are more than two formations for water disposal.
The focus has been on the San Andres – which has a long history of water disposal and is filling up – and the Ellenburger, which is more expensive and in some areas has high seismicity risk. Just like the Permian has multiple formations to produce oil and natural gas, it has some 47 formations that can take water, Adler said.
“There are a lot of other options,” he said. “You need to know where they are, what the possibilities are and what the risks are. We’re not going to run out of room to put water.” It’s important, Adler concluded, to understand the subsurface in order to know where to put water, not just find oil and natural gas.
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