Reducing fresh water needs at the Bakken play
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Equinor's Bakken asset has now successfully piloted a well stimulation using 100% returned water on two wells in Williams County, North Dakota. Our approach for such a test is unique among Williston Basin operators.
This comes just four months after receiving approval from the North Dakota regulatory body to conduct the pilot.
“If this pilot proves successful overall after total analysis we could have an opportunity to significantly reduce our environmental footprint and still maintain cost efficiency,” states Torstein Hole, senior vice president of US onshore (UON) in Development and Production North America.
“Continuously improving our operational practices is imperative to our overall onshore success—and technology plays an important role here.”
How it works
The aim of the pilot was to reduce the amount of freshwater used in developing shale resources, which can be as high as 4 million gallons per well in traditional hydraulic fracturing designs.
Through the research and development of technology, industry experts are now able to create the desired fluid viscosity, limiting water treatment to simple filtration at the wellsite.
The reduction of freshwater is achieved by utilising this technology to purify returned water, which contains impurities that exceed typical freshwater requirements for fluid systems used in hydraulic fracturing treatments.
“Equinor’s onshore business is part of the rapidly advancing shale industry, where technologies are constantly being developed and applied to improve results. Only two years ago, this achievement would have been unthinkable. Previous approaches in the industry to purify water have included very expensive treatment systems,” explains Bakken asset completions engineer Darren Schmidt.
“Now a minimal cleaning approach combined with an advanced fluid system has become the standard.”
Necessary steps
The full implementation of this pilot began in 2013, and has involved a significant level of collaboration with multiple service companies and the state regulatory body to seek the most environmentally robust and cost-effective solution.
In addition, the process required collaboration between production, facilities, completions and regulatory teams within the company.
“Because of the local storage and containment requirements in North Dakota, the operation necessitated the use of two locations,” Schmidt says.
“We stored returned water at one well location, and staged fracturing operations at the other. Our team chose to utilise the freshwater line between locations to transfer returned water underground, which is the safest way to transport between locations.”
This solution required the shut-in of a section of the freshwater line, and coordination of continued freshwater service to affected production operations.
In addition, all returned water in the vicinity of the location was redirected via pipeline from injection facilities to the fracturing location. This ensured the amount of water needed for a typical hydraulic fracture stimulation would be met.
“Because this was such a unique pilot operation, the team coordinated with regulators to create a thorough containment design and specific emergency response plan,” Schmidt says.
Additional benefit
Moving forward the team will work closely with the research, development and innovation (RDI) unit to watch production performance, complete ongoing laboratory studies and determine best practices in achieving the desired production, economic and environmental performance for wells with 100% returned water application.
“We are still at an early phase, but know on an annual basis there is roughly enough supply of returned water to meet the stimulation demands of our current operations,” states Schmidt.
“If we can prove commerciality of this pilot, freshwater reduction potential could be huge. We are excited to analyse the final results.”