Posted 5/26/15 (Tue)
By John D. Taylor
Rick Chaffee stands in front of a dozen enormous liquid storage tanks at a Salt Water Disposal (SWD) facility, a couple miles west of Crosby, explaining how saltwater, a byproduct of oil production, is handled there.
Chaffee is Secure Energy’s Facility Manager for Processing, Recovery and Disposal at the Crosby facility.
Chaffee is understatedly proud of the facility’s ability to take what is basically a hazardous oilfield waste and deal with it in a rational, controlled way, keeping people safe, yet furthering the development of the Bakken’s job-producing oil resources.
Secure’s Crosby SWD facility can handle up to 20,000 barrels – 840,000 gallons – of saltwater per day, Chaffee says, but it averages about 11,000 barrels – some 462,000 gallons – daily. Altogether, the facility can hold some 12.7 million barrels of saltwater. To get a visual sense of this, 5 million barrels of water represents a football field of water, about 2.5 miles high.
Strings of semi-trucks haul loads of saltwater to Secure’s Crosby SWD facility because regional oil wells produce two to six barrels of saltwater for each barrel of oil they pump out, according to Chaffee.
Some of the saltwater Crosby’s SWD receives is flowback, some of it produced water.
In addition, if the rock strata contains radium, then technologically enhanced naturally occurring radioactive materials (TENORM -- what was in Noonan’s filter sock dumping incident) could also be present in both flowback and produced water. Frequently, when produced water is rich in salty chlorides, it indicates radium is present.
Both produced water and flowback must be separated from the oil, and in many cases this is done with a battery of settling tanks located at the well site. Since oil is lighter than water, it floats, allowing it to be skimmed off. This oil goes to market, the water is trucked to a SWD, like Secure’s.
At Crosby SWD, Chaffee said, Secure also uses a battery of settling tanks. A dozen tanks are located on the west side of the facility, along N.D. 5. Ten of these tanks are for settling.
The SWD takes saltwater in at three pump houses located east of the settling tanks, Chaffee said, the first step of the cleaning process.
The pump houses send the water to the settling tanks – flowback to one set of tanks to sit longer; produced water to other tanks – and over time, solids settle, oil floats and saltwater remains in between.
Solids from settling go to a full service disposal facility, Chaffee said, like Secure’s 13-mile Corner site, where “mud” is spun out using centrifugal force, then run through filters. Any radioactive solids above 5 picocuries per gram, the Environmental Protection Agency’s standard for background radiation, is collected and taken to radioactive waste disposal sites in Idaho or Colorado. Other solids are landfilled at Secure’s 13-mile facility.
Back at Crosby SWD, skimmers gather the oil residue that floats to the top of the settling tanks and sends this into two oil-storage tanks. Secure sells this oil, Chaffee said.
Next, the settled water runs through a 10 micron filtration system, to remove any additional particles of waste. These filters, after 2,000 barrels have passed through, are changed and sent to a landfill
After processing this wastewater, the SWD pipes it as deep as two miles under the earth’s surface, into the Dakota Sands formation, a layer of deep earth Chaffee describes as porous rock, sand and saltwater, where it is safely out of sight and out of mind.
When saltwater is added to saltwater, the salt can become a super-saturated solution, Chaffee said, turning into a solid, like cooked sugar maple sap becomes maple syrup.
SWDS, county wide
Currently, Divide County oil wells are averaging about three barrels of saltwater per one barrel of oil produced, Chaffee says, so there is quite a bit of water returning to the rock strata.
Older oil fields continue to give more saltwater than oil, especially those near Lignite, and some in Tioga, too, Chaffee said. “They’ve done this since I’ve been a kid.”
Altogether, Divide County has about 30 SWD injection wells, North Dakota Industrial Commission (NDIC) records show.
Some are old, like Stoneview Township’s 1976-built Thomas Olson 1 SWD, operated by Condor Petroleum. Others came in with the oil boom, like Secure’s Crosby SWD, which was built in 2011, Chaffee said. Others are brand new, such as Secure Energy’s Peterson Disposal in Blooming Prairie Township, put into operation in February.
Blooming Prairie, Stoneview and Gooseneck townships all have three SWDs each. Hayland, Plumer, Border, Coalfield, Troy, Clinton, and Mentor townships have two each. Palmer, Smokey Butte, Sioux Trail, Twin Butte, Westby, DeWitt and Ambrose have one each.
Is it safe?
To send millions of gallons of saltwater some two miles deep into the earth and store it involves quite a bit of effort.
First, you have to drill a hole some two miles down into the earth, into the Dakota Sands rock formation.
Chaffee calls drilling technology “incredible,” thanks to fracking, and described how well drillers have the means to drill deep with incredible accuracy. For example, in a recent repair job, drillers were required to go down several thousand feet, hit an 8-inch pipe, shatter it and bring the pieces up, then replace the pipe. Their first shot is a couple of inches off the center of the 8-inch pipe, but their second shot hits the exact spot.
Next there’s groundwater to deal with. Most groundwater is found well above 2,000 feet.
For the first 2,000 feet of a saltwater injection well, when the saltwater pipelines travel through groundwater resources, Chaffee said, there are a number of safety factors built into the operation to prevent contamination.
First, two layers of heavy-duty piping – an exterior pipe protecting an interior pipe – are used to keep saltwater out of groundwater. The interior pipe is cemented in place by concrete. The exterior pipe is held in place in the bore hole by a specialized concrete, developed by Halliburton, and designed to mimic natural soil, yet block any upward flow of saltwater.
At the tip of this dual piping, a donut-like float, a pressure monitor, surrounds the two pipes and can alert SWD operators on the surface that saltwater might be backing up, pushing against the donut and raising the pipe. If any pressure is detected on the “donut,” Chaffee said, the injection process is shut down immediately.
On the surface, he said, Secure is “really careful.”
“If there’s anything over a gallon spilled, we respond,” he said. “Anything over a barrel, we call NDIC.”
An abundance of spill and containment barrels, with absorbent pads to soak up spills, and “boomers” made from absorbent pads, used to soak up larger spills are readily available in bins around the facility.
Two bermed containment areas – one surrounding the entire facility; another inside it, surrounding the holding tanks – protect the site. The interior berm can hold 15 barrels of saltwater, the exterior berm as much as half of everything in the tanks.
Also, to prevent water from the surface entering the injection well, all the rainwater and snow melt at the facility is contained and monitored. This goes into a small lagoon on the southwest corner and is monitored by NDIC. If it passes NDIC’s muster, it is pumped “over the fence.” If it doesn’t it gets treated again.
“If there’s a visible sheen on this water, we take care of it, clean it up,” Chaffee said.
Finally, and perhaps most important, is the constant monitoring done by Chaffee and his crew. Filters, pressures, pumps, flows into the well, nearly everything is checked at least once every two hours around the clock. If it isn’t working right, it is shut down.
Crosby SWD needs only 300 to 400 psi in pressure to inject saltwater into the deep earth. Other facilities require more pressure.
“Our network of water disposal wells discard fluids safely and responsibly,” the company’s website states. Chaffee says Crosby is proof of this because they have not had a single issue since opening.