The latest United States Geological Survey (USGS) and U.S. Energy Information Administration (EIA) data show that the number of “felt” Oklahoma earthquakes —those registering magnitude 2.8 or greater on the Richter scale — have continued to decline at the midway point of 2018, even as oil production in the Sooner State soars to record levels.
The monthly average of M-2.8 or greater earthquakes so far in 2018 is 76 percent below the monthly average in 2015, when seismic activity peaked in the state. In fact, the number of felt earthquakes this past June was 86 percent below Oklahoma’s most seismically active month of June 2015.
Felt seismic activity thus far in 2018 is also 21 percent below rates observed over the first half of 2017, continuing a steady downward trend that began three years ago after measures were taken to reduce wastewater injection volumes in seismically-active regions of the state.
These declines have come even as drilling activity has ramped up considerably in the state over the past two years. Oklahoma oil production has reached record levels — 17.7 percent above 2015 monthly production — while average weekly rig counts have increased nine percent. Put another way, seismic activity in Oklahoma continues to trend downward even as shale development booms in the Sooner State, further dispelling the misleading media narrative that fracking is to blame for the state’s increased seismic activity.
In its latest effort to clear up public confusion regarding the distinct differences between hydraulic fracturing and wastewater disposal the USGS recently noted:
“Only a few of the over 2000 magnitude 3 and larger earthquakes since 2009 that have occurred in Oklahoma have been connected to hydraulic fracturing. The majority of earthquakes in Oklahoma are caused by the industrial practice known as “wastewater disposal”. Wastewater disposal is a separate process in which fluid waste from oil and gas production is injected deep underground far below ground water or drinking water aquifers. In Oklahoma over 90% of the wastewater that is injected is a byproduct of oil extraction process and not waste frack fluid.”
The Oklahoma Corporation Commission has also explained:
“Most of the wastewater comes not from hydraulic fracturing operations, but rather from producing wells. The water exists in the producing formation and comes up with the oil and natural gas.”
A vast majority of Oklahoma wastewater is what is known as produced water, also called brine or formation water. Brine is co-produced along with oil and natural gas by virtually every well in the United States, regardless of whether the well has been hydraulically fractured or not.
The Tulsa World recently reported that wastewater injection volumes in earthquake-prone areas of Oklahoma have declined roughly 63 percent (3 million barrels per day to 1.1 million barrels per day) from their 2014 peak.
How can this be happening at the same time shale development is surging in the state?
Not only did Oklahoma regulators implement measures in 2015 that either shut in or reduced volumes of injection for more than 700 disposal wells throughout a 15,000-mile “Area of Interest” — reducing wastewater injection volumes 40 percent from 2014 levels — development in the state has also shifted from the Mississippi Lime formation to the SCOOP and STACK formations.
Wells developed in the Mississippi Lime typically co-produce a large amount of saltwater, sometimes 10 to 15 barrels for every barrel of oil produced, according to Oklahoma Geological Survey (OGS) director Jeremy Boak. Back when oil prices were above $100, such wells suddenly became far more economical, leading to an increase in drilling in these regions and, subsequently, a significant increase in produced water from day-to-day production that needed to be disposed of in Class II disposal wells.
In contrast, the SCOOP and STACK formation yield far less co-produced saltwater than the Mississippi Lime, and most formations in general. Even though wells developed in the SCOOP and STACK typically require hydraulic fracturing to be brought into production, the fact that they produce little brine — and subsequently less wastewater disposal volumes — explains why seismic activity in Oklahoma is decreasing significantly even though production from the region is booming.
Coupled with the fact that wastewater disposal from the Mississippi Lime formation has decreased dramatically, some researchers are optimistic that Oklahoma seismic activity could return to background levels in the near future.
This data is just the latest evidence that pragmatic mitigation measures to address Oklahoma’s induced seismicity are proving effective, a sharp contrast to calls by “Keep It In the Ground” groups to ban oil and gas development in the state, an extreme measure that would have devastated Oklahoma’s economy.
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Source: Energy In Depth