Overall oil and gas production remains sluggish compared to the industry’s 2014 peak, but, off the top of your head, name some unconventional plays that remain busy.

Well, there are the Permian Basin and the Marcellus Shale, of course.

Don’t forget the Midcontinent’s Stack (the Sooner Trend, Anadarko, Canadian and Kingfisher) that sprawls across northwestern and central Oklahoma. It’s the busiest part of the still-perking up Midcontinent region, which also enjoys fairly good activity in the Scoop (South Central Oklahoma Oil Province), Arkoma/Woodford and elsewhere.

A closer look at the Stack reveals it is, in fact, something of a small-scale Permian. Consider that both:

  • Are established producing regions that had strong conventional production for decades;
  • Enjoy significant midstream assets in-place;
  • Had steadily declining conventional output until the advent of the shale plays in the past decade; and
  • Both are geologic layer cakes with multiple pay zones that could bless producers with bankable reserves for years to come.

Both remained (comparatively) busy during the depths of the 2015-2016 downturn.

Multi-play/multipay

Derricks have soared above the plain—where the wind comes sweeping down -- for years, and the Sooner State’s surging crude oil production fueled the nation’s fight in World War I. Several big energy names, such as Conoco, Phillips and Citgo, got their start here. Tulsa and Oklahoma City continue to provide bases for dozens of energy firms.

But what about midstream infrastructure? Some of the very first NGL separation plants went up in Oklahoma more than 100 years ago. And there’s a reason why Nymex chose the pipeline crossroads of Cushing, Okla., as the delivery point for industry-benchmark West Texas Intermediate crude (WTI).

Today, the Midcontinent sports dozens of gathering systems, gas processing plants, pipelines of every kind, abundant oil and gas storage and several refineries.

And, about that hydrocarbon layer cake--a Stratas Advisors report on the Midcontinent categorized “the Woodford as a top-tier play within the Midcontinent region that is predominantly composed of the Anadarko, Ardmore and Arkoma basins, with the majority of current development activity occurring in the Anadarko Basin. There are multiple stacked formations within this region that are conducive to hydrocarbon trapping and recovery, including the Meramec, Woodford, and Springer formations.”

The Stack story

The bigger Permian and Marcellus may cause some to overlook the Stack. But witness producer Devon Energy Corp.’s July announcement that its Privott 17-H well in southwestern Kingfisher County, Okla., flowed a “facility-constrained” 6,000 barrels of oil equivalent per day (Mboe/d) in tests of the Meramec.

“Facility-constrained” means that, yes, the well could have done even better, there’s more on that, below.

“When compared against publicly available data in the Stack, the Privott well achieved the highest initial production rate of any well by a wide margin and is expected to recover in excess of 2 million barrels of oil equivalent [MMboe] over the life of the well,” the Oklahoma City-based producer said.

The well has a 10,000-foot lateral in the Upper Meramec with a 50:50 oil/gas cut. Do the math, and the gas component alone works out to 18 million cubic feet per day (MMcf/d). The Privott well is definitely a keeper, and is no fluke. Last December, Continental Resources Inc. said its Angus Trust 1-4-33XH well flowed 4,642 boe/d on test with a 55:45 gas-oil ratio. It has a 9,800-foot lateral. The well, in Blaine County, Okla., was immediately north of Continental’s Boden 1-15-10XH well, also in Blaine County. Boden 1-15-10XH flowed 3,508 boe/d with 28% oil, while both wells tapped the Meramec.

EnLink Midstream knows how good the Privott well is since its gathering system serves it, Ben Lamb, executive vice president of corporate development, pointed out to Midstream Business. And about that facility constraint, Lamb noted that “we had a standard 4-inch meter out there because neither of us, I think, really knew what to expect. We had to go out and install a second parallel meter to handle that single well.

“Our big lesson from the year so far in the Stack is just how much better the resource is than we initially thought it was,” Lamb said. “Look at our biggest customer, Devon. They’re talking about going into full field development mode starting with their Showboat project, which is expected to spud later this year. This means increased cash flow for us early next year.”

Showboat, in western Kingfisher County, will have about 25 wells across two drilling units, each with four landing zones in the Meramec and Woodford. To the south in Canadian County, Okla., Devon has two other big drilling programs underway—the 39-well Hobson Row project in five sections started production in the first quarter and Jacobs Row, which will have as many as seven drilling units, will start drilling in the fourth quarter.

“When EnLink significantly expanded in the Stack via a large acquisition in early 2016, we had no idea that there were going to be four landing zones that could be co-developed in the same section,” Lamb said. “We were hopeful that we would get two — maybe the Meramec and the Woodford but maybe not both everywhere. Our expectations were exceeded.”

With its second-quarter earnings, EnLink announced an expansion of its Stack infrastructure—Black Coyote—to gather crude, primarily from the Showboat project.

More cake

“Devon also brought online four additional high-rate Meramec wells in the core of the over-pressured oil window during the second quarter that benefitted from the company’s recently enhanced completion design. In aggregate, these four wells attained an average 30-day initial production rate of 2 MBoe/day. These well results were even more impressive on a per-lateral-foot basis with average well productivity of greater than 300 Boe/d per 1,000 feet of gross perforated interval,” the company added in its Privott announcement.

Alongside Devon, count other big producers, such as Continental, Cimarex Energy Co., Newfield Exploration Co. and Marathon Oil Corp., all with ambitious drilling plans for their Stack acreage. Plus, numerous smaller, private firms have plans of their own.

“There are people who are just beginning to figure out how good it can be,” Lamb said of the Stack, who then discussed that Permian comparison.

“Now clearly, there are differences. One difference is the areal extent of the Stack, as we know it today, is not as large as the areal extent of the Permian. However, the quality of the resource may be just as good or even better than what we have in the Permian. I’ve been saying for a while—and I’m not the first to say it—that the Stack is today where the Permian was around three years ago. There is so much opportunity,” he added.

Just say ‘Stack’

With flow rates like those above, it’s easy to understand why many industry analysts’ reports have “Stack” and “Permian” in the same sentence. Jefferies Group sponsored a “Stack attack” investor of the Midcontinent at the end of the second quarter and reported positive findings in visits with producers, oilfield service (OFS) companies and midstream operators.

Jefferies analysts reported “sustained activity remains the tone from Oklahoma in our investor tour meetings. E&Ps stressed breakevens of less than $40/bbl in their best locations and optimization potential elsewhere. Tightness in hydraulic fracturing points to further pricing gains and more customer-dedicated fleets. Midstream companies look for their volume-driven cash flow growth to help equity performance vs. strong oil price correlation since the start of the downturn.”

The report added, “Productivity of wells has been greatly improved from enhanced completions (shorter stage spacing, higher proppant loading, etc.). Operators suggested that work on that front is now optimizing rather than enhancing, as the focus is less on increasing the size of the frack and more on finding the best ‘recipe’ of inputs for each section of rock. We would not rule out the ability of the industry to continue improvements, but it feels to us that operators believe they are nearing the latter stages in productivity gains barring a step-change in technology.”

For the midstream sector, “Despite significant crude price volatility over the last several weeks, the midstream companies we met with shared similar views to their E&P and OFS counterparts on the energy market. While WTI prices hover in the mid-$40s and investor sentiment has grown bearish, field-level activity remains robust and there are no discussions of slowing the growth profile in the near-term. Recognizing the relationship crude prices have had on the equity performance since the time of the November 2014 OPEC announcement, to-date … the companies we met with believe investors will soon shift their attention to the volume-driven cash flow growth, and this should lead to stronger equity performance as a result.”

Kristina Kazarian, research analyst at Deutsche Bank, has referred to the Stack and Scoop as her “favorites,” along with the Permian, in recent research. Wells Fargo and Barclays research routinely mention the Permian alongside the Stack and Scoop.

Barclays opined in a recent report that “though no longer receiving the attention it enjoyed just a year ago, there have also been a number of interesting developments in the Scoop/Stack lately aimed at serving various needs on the gas and NGL value chain, particularly for dry gas and NGL takeaway from the basin and for the rich gas service to underutilized processing facilities outside the plays.”

Yes, that opinion followed a lengthy Permian discussion.

“I’ve seen published the relative returns on the Midcontinent and Permian, which seem to be the two that everyone's focusing on right now,” Craig Harris, executive vice president and chief commercial officer at Enable Midstream Partners, told Midstream Business. “At $45 crude, you’re able to make a good living if you’re a producer in the Stack and Scoop.” That creates “a lot of resilience from a pricing standpoint” that draws producers.

Infrastructure in place

That bullet point on great midstream infrastructure means cash starts flowing more quickly when a producer turns on a well. A new well may be just an easy mile or so from an existing gathering system.

Enable Midstream doubled the size of its Bradley processing plant in Grady County, Okla., in 2015 to 400 million cubic feet per day to handle increasing production from the north end of the Scoop play. (Source: Enable Midstream Partners LP)

Wells like the one Devon announced can challenge some midstream providers, Ryan Lewellyn, president and CEO of Tall Oak Midstream, told Midstream Business. Granted, it’s a nice problem to have.

“I think the biggest challenge is making sure—if you’re a producer—that you have the right midstream solution that can accommodate your needs and get production to the highest-value markets,” Lewellyn said. “That’s one thing we’ve focused on, making sure we have all the right residue outlets at our plant so we can get premium pricing for our customers’ gas — not just move it to market.”

Infrastructure means more than pipelines and tanks, Lewellyn noted. The Midcontinent has the same headaches other booming regions have.

“The biggest challenge is residue [gas] capacity. There are limited residue takeaway options out of the Stack and that’s driven by both the Scoop and the Stack being on top of each other. The new flush of production has constrained residue markets.”

But infrastructure could better for one midstream segment, he noted.

Work is underway on the expansion of Tall Oak's Carmen processing plant in Alfalfa County, Okla. (Source: Tall Oak Midstream)

“Kingfisher County, and so many great towns and areas in the region, have roads that are not built for the amount of trucking activity they’re seeing,” he said. “So I think the next thing that’s going to have to happen is, as these producers go into production mode and the Stack is more robust, is better oil gathering and water gathering at the wellhead. That means new pipelines, because the roads just cannot support the amount of trucks that it takes to service that kind of drilling and production activity we’re seeing.”

The rig count

“The thing that's been most intriguing about the Stack is, even as oil prices went from $100 to $30, rig counts were going up. Along with the Permian, it was one of the only areas in the country that saw this kind of sustained increase. Then, as we went from $55 and $60 and back down to $45, rig counts continued to rise in the Stack. It just points to the fact that it’s economic even when prices are closer to the low-$30s. So even when times are tough on the commodity price side of the equation, rigs tend to high-grade to the best areas,” Lewellyn added.

“Production continues to accelerate in the northwest Stack as producers develop liquids-rich formations including the Meramec, the Osage and portions of the Cana-Woodford,” he said.

Tall Oak primarily serves Oklahoma’s Major, Dewey, Custer, and Woodward counties, as well as a portion of northern Blaine County.

“The economics and long-term viability of the area are very strong, and we continue to see producers focus their capital on the Stack. We are leveraging our successful track record in the play to rapidly expand the capabilities of our Midcon system. Our team is dedicated to staying ahead of producer needs for high-quality gathering and processing infrastructure and for securing premium markets for their products.”

Doing that requires a major capex commitment by Tall Oak Midstream II, which operates the current system. The firm sold its original system, Tall Oak Midstream I, to EnLink Midstream in early 2016 for $1.55 billion. That system serves portions of the Stack and Cnow (Central North Oklahoma Woodford) plays.

“Producers have dedicated some 500,000 net acres in the Stack to Tall Oak, which purchased Caballo Energy’s Eagle Chief system in July 2016. Since then, it has expanded the system’s gathering network by more than 100 miles to approximately 700 miles total,” Lewellyn noted.

Tall Oak II has two processing plants, Carmen and Eagle Chief, in Alfalfa County, Okla. with a combined capacity of 60 MMcf/d. It recently started construction on a second train at Carmen that will add 200 MMcf/d of cryogenic capacity. The firm could eventually offer producers 500 MMcf/d of throughput if production warrants.

In July, the company announced the formation of Tall Oak Midstream III LLC with an initial equity commitment of up to $200 million from EnCap Flatrock Midstream and Tall Oak management. Tall Oak II will continue focusing on operating and expanding its midstream assets in the northwest Stack, according to Lewellyn. Tall Oak III will pursue midstream opportunities across North America outside that portion of the Stack.

Enlink’s commitment to the Midcontinent shows prominently in its capex budget.

“Our capital number that we’ve shared publicly this year for Oklahoma is $360 million to $460 million, and that’s out of a total budget for our company for growth capital of $610 million to $770 million,” said Lamb. “Central Oklahoma is far and away the biggest area where we’re investing capital as a company this year.”

Canadian Valley

ONEOK Inc. recently announced that it plans to double the capacity of its Canadian Valley gas processing plant in the Stack to 400 MMcf/d. The Tulsa, Okla.-based company’s Canadian Valley II project at its plant in Canadian County, Okla., is projected for a late-2018 completion.

“The expansion and related infrastructure is expected to cost approximately $155 million to $165 million and is supported by more than 200,000 acres of dedication, primarily fee-based contracts and minimum volume commitments,” ONEOK said in its expansion announcement.

The work, in conjunction with a recently announced 200 MMcf/d firm offload agreement to a third-party processor, will bring ONEOK’s total Oklahoma gas processing capacity to about 1.1 billion cubic feet per day (Bcf/d) by 2019, the company noted.

“Additionally, NGL produced from the expansion are expected to add approximately 20,000 bbl/d per day of additional volumes to ONEOK’s existing Oklahoma NGL gathering system,” it said.

ONEOK told attendees at a recent analyst conference that its Midcontinent gas network now has a 1.8 Bcf/d capacity, serving 34 gas plants. It also has 50 Bcf of gas storage at sites in Oklahoma and Creek counties. ONEOK has 200,000 Stack acres dedicated to its system, served currently by 700 MMcf/d in processing capacity.

Enabling the plays

Oklahoma City-based Enable is another big midstream player in the Midcontinent, with processing capacity of nearly 1.5 Bcf/d in the Stack and Scoop. But that’s not enough, Harris said. Its Wildcat project will add 400 MMcf/d of capacity by moving production south for processing at Energy Transfer Partners’ Godley Plant in Johnson County, Texas—built to handle Barnett Shale production.

Service is scheduled to start by the end of second-quarter 2018.

“We’re very proud of this project,” Harris said. “We think it is a prime example of one of Enable’s strengths, which is efficient use of existing infrastructure. You know, the Anadarko—the Stack—is not a new play; it’s been around a while. It has a lot of existing infrastructure. We’re pleased to own a very large footprint of that, and Wildcat is just a way to utilize not only our existing infrastructure but that of some others. That’s one of the things you’ll hear from us, the ability to provide efficient service using our existing assets—and that’s what Wildcat is.

“We are using our existing assets to get the gas, then we will be able to wheel gas from the Stack into the Scoop and then, with a modest extension, hook that up to Energy Transfer Partners from Ardmore, Okla., down into the Barnett system,” he added. “It’s a very efficient way to get gas out of the basin, which is one of the current themes that’s going on. We are seeing a tightening in the system and the need to get gas out.”

Superior infrastructure
Superior Pipeline Co. LLC, the midstream portion of Unit Corp., has been a major Midcontinent operator for years. Bill Ward, senior vice president of commercial activity, told Midstream Business the company had the good fortune to invest in Midcontinent assets early on as the unconventional plays developed.

“We can handle what we have right now,” he said. “We have spent a lot of capital in recent years providing central delivery points for our producers, and they have been connecting to us. We’re harvesting what we sowed. We built some facilities early on and we’re benefitting from that now. Our plants continue to attract new volumes and there is the possibility of expansion based on drilling results.”

In addition to the Stack, Superior’s assets serve northern Oklahoma and southern Kansas producers. Producers have dedicated nearly 1 million acres to Superior in this region. It has an estimated 200 miles of gathering lines connected to its Bellmon and Reno processing plants, which have a combined capacity of 115 MMcf/d.

The ‘Merge’ emerges
Oklahoma enjoys its own jargon-rich energy language. For example, watch for news about Newfield Exploration’s Score play (Sycamore, Caney, Osage, Resource Expansion). Another new term on the lips of the industry is “the Merge.”

When asked about the Scoop activity, EnLink’s Lamb said it depends on what you mean by the Scoop, the oily unconventional play that lies generally south and east of the Stack.

A Sunoco Logistics truck waits to take on a load at a Stack play tank battery. Sunoco operates a crude oil gathering system across northern Oklahoma that links the region's producers to the Cushing, Okla., trading hub and the Holly Frontier refinery at Tulsa, Okla. (Source: Hart Energy)

“We are not active in the old part of the Scoop; Garvin County [Okla.] and down that way,” he said. “But there's an emerging area between our area of activity in the Stack and the north part of the Scoop that some people call the ‘Merge.’ We have an outstanding position in the Merge in southern Canadian County through the northern half of Grady County [Okla.]. We have two major dedicated producers in this area who are doing really exciting things.

“The Merge has been a real bright spot for EnLink,” Lamb added. “It’s an area that we didn't really think that much about 18 months ago. It was on the fringe of our position, but it has proven to be extremely promising for our business. The wells have been really, really good in this area. There are a couple of good targets in the Merge, but a lot of it is in what is called the ‘Sycamore,’ which is similar to the Meramec in the core of the Stack.”

Superior’s Ward is another midstream observer who advised to watch the Merge.

He added, “The Merge is the new battle cry, but it hasn’t been tested as much as the Stack. Although they don’t have as many rigs in the south currently, I think producers are still testing their results. They’re still poking holes in the ground to see what they’ve got.”

Tall Oak doesn’t serve the Scoop, but Llewellyn is positive about its prospects. “The Scoop continues to be a great producer,” he said. “It seems that now all the acreage is being held and the producers down there are drilling great, liquids-rich gas wells.”

Mainline Midstream LLC, a wholly owned unit of Riverstone Holdings managed by Mainline Energy Partners LLC, announced in August it had acquired more than 1,000 miles of oil and gas pipeline and right-of-way in the Scoop/Stack/Merge.

In announcing the purchase, Mainline called the Midcontinent plays “economically attractive, and our strategy is to develop infrastructure in the play, providing outlet optionality and allowing producers to focus on the drillbit and invest their capital efficiently."

The Stack and Merge may be getting the most attention, but there’s still good activity to the south in the Scoop region. Also in August, BNK Petroleum Inc. announced encouraging results following fracking of its Hartgraves 1-6H well in the Tishomingo Field on the Scoop’s south side and said it would announce IP rates in September.

Head east
Oklahoma’s topography changes from the flat Great Plains to heavily wooded hills going east, but in either place the drilling prospects are similar. There may be new life emerging from eastern Oklahoma’s Arkoma Basin, where the same Woodford that supports much of the drilling activity across the prairies lies below ground.

“One of the more interesting things we’re seeing in the Midcontinent is to the east in Hughes and Pittsburg counties [Okla.] in the Arkoma,” Llewellyn said.

EnLink’s 200 MMcf/d Northridge gas plant and a 140-mile gathering system support production in Oklahoma’s Coal and Hughes counties. Lamb noted Northridge is “an asset that over the last couple of years hasn’t seen all that much activity, like most assets in the Arkoma.” However, that may be changing.

“I don’t want to say too much too soon, or to count our chickens before they hatch, but I’ll just say that we have seen a resurgence of interest among the producer community for the service that we’re able to provide with our Northridge system, and we think that there are some positive opportunities in Northridge’s future.”

Superior’s Panola system serves Arkoma E&Ps, including its sister producer, Unit Petroleum Co. Superior also has seen a modest uptick in throughput for its system centered on Wilburton in Oklahoma’s Latimer County, said Ward.

“It has been pretty quiet, although Unit has production over there. I’ve heard spits and spatters, things may be picking up,” he added.

Cnow, not later
Much like the Arkoma, northern Oklahoma’s recently quiet Cnow seems to be coming back to life.

Tall Oak got its start in the Cnow with the system it sold EnLink in 2016, and Lewellyn has kept a close eye on the region—although Tall Oak is not a midstream service provider there anymore.

“There’s activity in Payne County [Okla.] The story there is that while producers don’t see huge results, drilling costs are very low,” he said. “It can still be economic because it’s a shallow area. The Woodford is a lot shallower there, so you can target the Mississippian zones just on top of the Woodford and complete a well for $1.5 million to $2.5 million.”

He added that if and when crude prices rise in “the $50- to $55-plus range, that’s really going to help everyone” in the Cnow.

Take it away
The Midcontinent’s strong infrastructure allows midstream operators the ability to offer customers great optionality, several industry executives told Midstream Business. Gas liquids can move easily to either of the nation’s major NGL hubs—north to Conway, Kan., or south to Mont Belvieu, outside Houston.

EnLink offers a third option: Louisiana.

“We have an integrated liquids business that spans Mont Belvieu to the Louisiana market,” Lamb said. “For the most part, our liquids are going down out of Oklahoma to Mont Belvieu. Then, we transport them to EnLink’s fractionation complex in Louisiana that primarily serves the Mississippi River markets. At the point where we fill those fractionators up, we will have obviously a scale position of liquids in Mont Belvieu and may think about expanding our asset base to include Mont Belvieu-based fractionation.”

Residue gas capacity, as Enable’s Harris noted, is an issue as production grows but Oklahoma’s central location offers optionality on multiple transmission systems. Additional transmission system capacity may be in the works.

And what about crude oil?

Did we mention Cushing?

An oil producer cannot ask for a better market, and one from, say, Kingfisher or Grady counties, since Cushing is right over there.

And, check off the inland refineries at Ardmore, Ponca City, Tulsa and Wynnewood, Okla.; Coffeyville, Kan.; and Borger and McKee in the Texas Panhandle. Yet, ten years ago those plants had marginal economics because they relied on imported feedstock piped up from the Gulf Coast. Not anymore. Much like when they first opened around 90 years ago, there are pumpjacks outside the plant fences. They have very attractive economics, and crude transportation costs are minimal as a result.

They all feed into established product pipeline systems operated by Magellan Midstream Partners LP and Explorer Pipeline Inc., among others.

Looking ahead
So as the Midcontinent in general—and the Stack in particular—ramp up, what do industry observers see in the near future?

Michael W. Hinton, chief strategy and customer officer for commodities trader Allegro Development, told Midstream Business he’s very positive on the Midcontinent because of comparatively low costs.

“Improved technology continues to bring costs down to the point that newly drilled wells are profitable at $40/bbl market prices,” he said. “Since shale wells pay off in a relatively short time period of two to three years, one can expect drilling activity to remain at current levels or higher. Prices would have to dip well below $40/bbl for a sustained period of time to significantly impair the drilling activity.”

But there are challenges to the midstream as the positive trend continues, Hinton noted.

“The expansion and building of new gathering systems, pipelines, terminals and stations to handle the new production is lagging far behind the growth in production. In fact, due to the nature of shale oil wells’ production profiles and their locations, many will never be connected to pipelines. This means that significant truck- and rail-based transportation will continue for many years to come. This presents huge logistical challenges,” he added.

The unconventional Midcontinent plays “continue to grow, and we are continuing to see an increase in activity,” Enable’s Harris said. “These plays continue to get delineated, and the footprints continue to get larger.”

It’s the same thing that has been happening in Appalachia, he added, an area he knows well from previous assignments. “You continue to work through the rock. You continue to find incremental opportunities. The Merge is now a developing play in the Anadarko, and we’re starting to see drilling activity in that area.”

EnLink’s Lamb is equally upbeat.

“Certainly, I don’t expect every well is going to be a Privott. But just the fact that there’s a well that good, I think, obviously speaks for the quality of the resource,” he said.

“Plus, look at what Newfield, another customer of ours, is starting to do in the area. Everyone understands that the Meramec is exciting and the Woodford’s exciting. Newfield is starting to test the Sycamore, the Caney, the Osage-- some of these other horizons that haven’t been really delved into yet. We’ll see if there’s further expansion of the resource if some of those horizons turn out to be as economic as the Meramec and the Woodford.”

As promising as the Stack is, it won’t ever be equal in size to the much bigger Permian, Lamb emphasized. EnLink operates in both regions, so he can easily draw some comparisons. “The question is, just how big is the ultimate opportunity?” he said of the Midcontinent. “It looks extremely promising, and EnLink is right in the middle of it.”

Paul Hart can be reached at pdhart@hartenergy.com or 713-260-6427.


Produced Water
Still A Shaky Issue

Water handling represents a big question mark in the Midcontinent, given Oklahoma’s number of water injection-induced earthquakes. The rash of tremors has led the Oklahoma Corporation Commission to order several water injection wells shut in.

Craig Harris, executive vice president and chief commercial officer at Enable Midstream Partners, said thus far the Midcontinent’s midstream operators have not become heavily involved in water.

“We do not deal much with water handling. Most of our producers deal with their own water,” he said. “Some people are starting to look at it as an alternative to heavy truck traffic in some areas.”

But for whoever handles the millions of barrels of frack water and produced water, it’s a problem, given the particular geology of the region. Many injection wells were found to be lubricating long-dormant faults in the Arbuckle Formation, making the Midcontinent’s historically quiet geology shudder.

In August, eight earthquakes strong enough to be felt occurred in one day. The biggest, rated at 4.2 on the Richter scale, was centered on Edmond, an Oklahoma City suburb, according to the U.S. Geological Survey.

Oddly, these new quakes were not near other tremors of recent years. The agency noted that its current “investigation is focused on oil and gas wastewater disposal wells that inject into the Arbuckle Formation, the state's deepest formation. The earthquakes have been clustered close together in an area where there is a known fault. There are no Arbuckle disposal wells at or very close to the location” of the August quakes.

Oklahoma’s rash of earthquakes peaked in 2015, with more than 900 tremors rated 3.0 or higher. In January 2016, Gov. Mary Fallin approved funding to expand efforts to address the issue.

—Paul Hart