People often ask about America’s shale plays and what makes them different when it comes to how produced water is managed. With activity in all basins on the rise, now is a valuable time to discuss this topic.
Each play has its own challenges, but also unique opportunities. Produced water management is different in each play either due to disposal cost, fresh water availability, regulations, induced seismicity, or all of the
above. Although each play is different, there are many similarities. Here’s a summary of each play’s respective water management approach.
Unique in many ways, the Marcellus is primarily a gas play. It has the highest produced water disposal costs as there are few disposal wells in Pennsylvania. This is not because of restrictions but geology. The lack of disposal wells in Pennsylvania means most produced water is trucked across state lines. In Ohio, where water has been trucked, new reports of induced seismicity have restricted disposal wells, driving up costs.
Produced water volumes generally decline for wells in the Marcellus. However, with few treatment and recycling facilities in Pennsylvania, there is far less capacity than is needed. Produced water pits are difficult to permit and uncommon resulting more aboveground tank storage.
With higher disposal costs for operators and well permit requirements, most produced water is recycled in Pennsylvania even though fresh water is abundant and cheap. Companies generally use slickwater for hydraulic fracturing. The average frac uses about 275,000 bbl and roughly 90 fracs are completed each month.
Water salinity in the Bakken is among the highest of any play. Here, operators rely on on disposal wells more than any other play even though it is primarily a fresh water play. Produced water recycling rates in the Bakken
are among the lowest.
North Dakota is renowned for its cold winters. As a result, weather is a bigger consideration here than in most other plays. Fresh water is also abundant and cheap and that tends to offset the need to recycle.
Completions in the Bakken have transitioned from mostly crosslink gel and hybrid fracs to slickwater, one of the most dramatic frac method changes of any play. Slickwater has gone from 20 percent utilization in early 2016 to more than 60 percent in 2018. In other plays, transition to slickwater is typically followed by an increase in recycling, but that has not occurred in the Bakken. Average frac is about 200,000 bbl. and about 90 fracs are run each month.
SCOOP and STACK
Oklahoma’s SCOOP and STACK plays also rely heavily on disposal wells for produced water. However, concerns over induced seismicity have affected this play more than any other. Regulations now limit the number of wells within certain geographical areas. These rules are designed to reduce the density of disposal wells but are also driving up the cost of disposal.
As in the Bakken, in the SCOOP and STACK there has been a shift from gel fracs and hybrids to slickwater, but the change is not as dramatic as it is in the Bakken. Slickwater was used in about 20 percent of fracs in early 2016 and that grew to about 50 percent in 2018.
Several produced water recycling projects are planned here and the number is expected to continue growing. There are reports of local agency opposition to use of lay-flat hose for produced water transfer along roadsides and this may stall or slow down some recycling projects. Evaporation is being seriously considered here as well. A government and oil companysponsored study evaluating the economics of evaporation technologies was recently completed.
The average frac is about 275,000 bbl. and about 100 fracs are completed per month, nearly doubling the number of completions run in early 2016 when the average was about 50 fracs per month.
In south Texas, the Eagle Ford play shows some of the lowest salinity water. As a result, the Eagle Ford and Powder River Basin in Wyoming are probably the best candidates when considering discharge-quality produced water because of the lower salinity. Recall that higher salinity waters limit conventional desalination options.
Eagle Ford wells generate a low ratio of produced water and flowback. This partially explains why recycling was not encouraged. Slickwater accounts for more than 50 percent of all frac completions. The average frac is about 250,000 bbl. and there are more than 160 fracs completed each month.
By sheer volume, the Permian is by far the largest of all shale plays. Unlike others, waterflooding provides a significant outlet for produced water. Disposal wells are also prevalent. The ratio of produced water to oil is greatest in the Permian. A few years ago, the ratio was more than 8:1. Today it is closer to 4:1. Because of the high ratio the total produced water generated in the Permian is between 450 and 500 million bbl. per month. However even as frac counts increased, the water to oil ratio has trended down and older wells are seeing a decline in produced water generated.
Remarkably, the increase in the Permian well count has not significantly moved the needle on overall produced water generated each month. Produced water volumes are more than double the water required for fracturing operations in the Permian. So even if 100 percent of produced water was recycled the need for alternative uses would remain.
Today, those alternatives include waterflooding and disposal wells. Of the total frac water demand from all plays across the U.S., the Permian accounts for 60 percent. With a lack of available produced water in other plays, the Permian accounts for at least 75 percent of the total produced water market.
Although slickwater is the most prevalent frac method in the Permian, it accounts for about half of all fracs completed. There are concerns that some Permian disposal zones are pressuring up, but others are not. More than 400 fracs are completed each month and the average frac uses more than 500,000 bbl.
Considering those facts, it is obvious why the Permian is king when it comes to water management.
Other plays are not covered here due to less activity. They include: the Barnett, Fayetteville, Haynesville, Mississippi Lime, Niobara/DJ Basin and Powder River Basin. Of these, the Powder River is gaining some steam and by next year, could see a place among the major plays.
In our discussion of each major play, we noted the increase use of slickwater in frac operations. Why is this important? Slickwater is the frac method most compatible with produced water making the decision to use recycled produced water much simpler.
The higher salinity of produced water can increase friction, but an increase in the dose rate of friction reducer is all that is needed to com pensate. Salt-tolerant friction reducers are more expensive but allow up to 100
percent produced water fracs.
Gel fracs are much less compatible with produced water. Switching from gel fracs to slickwater can allow the operator to double or even triple the amount of produced water per frac. Gel fracs don't allow more than 30 percent produced water; slickwater fracs can go to 100 percent.
There are many salt-tolerant gels and different crosslinkers that allow for 100 percent produced water gel fracs, but higher costs have limited this practice while 100 percent produced water fracs with slickwater are becoming more common.
In the Bakken, where the most dramatic shift to slickwater fracs has taken place, there is no change in produced water recycling due to plentiful, inexpensive freshwater and high-saline produced water.
In the SCOOP and STACK plays, recycling has increased due to more slickwater fracs and new restrictions on disposal.
In the Permian, the transition to slickwater and scarce freshwater has driven recycling growth.
Each shale play comes with plentiful opportunities and each has its own challenges. But for sheer size, the king of all plays continues to be the Permian.
Authored by Mark Patton
Mark Patton is president of Hydrozonix. He has more than 25 years’ experience in the development, design, implementation and operation of treatment technologies. Mr. Patton’s oil and gas background includes treatment systems for waters, wastewaters, drilling muds, tank bottoms and process residuals. He holds one produced-water patent with two additional patents pending.
Mr. Patton earned his B.S. in chemical engineering from the University of Southern California in 1985.