Disposal of water recovered from wells that have been hydraulically fractured has become the subject of intense scrutiny from both the public in general and regulatory agencies these days.
“The use of the large volumes of water (for injection) often stresses local fresh water supplies, and the water flowing back from the well after fracturing is a briny mixture, creating a water disposal problem,” noted Paul Ziemkiewicz, director of the West Virginia Water Research Institute at West Virginia University (WVU).
Help is on the way.
An ongoing project at WVU is confronting the dilemma, with participants readying to apply a technology at the well site to resolve these issues, while assuaging expressed concerns.
The WVU research team has been evaluating methods for managing frack water withdrawals and returns from large gas wells in the Marcellus shale by converting the briny wastewater into a suitable, partial replacement of the fresh water that is currently used as the fracturing fluid of choice.
“The objective of this two-year, two-phase project is to develop and demonstrate a process for treating return frack water (RFW) from Marcellus horizontal well development that will allow an increased recycle rate, while decreasing make-up water and disposal well requirements,” Ziemkiewicz said. “It will be applicable in other places as well.”
Ziemkiewicz is principal investigator of the program, dubbed “Zero Discharge Water Management for Horizontal Shale Gas Well Development.” The effort is being funded by the U.S. Department of Energy NETL as a result of WVU’s response to an RFP issued by the agency.
The WVU research team submitted a proposal with the support of McLean, Va.-based FilterSure Inc. They had prior experience working with the principals there.
First Phase Results
During Phase I of the project, which was awarded in 2009, treatment options were evaluated for recycling RFW using actual Marcellus shale RFW.
That phase concluded with a decision to construct a prototype mobile unit based on the patented FilterSure modular multi-media technology.
“We’re tweaking it and adjusting the media to its multi-media filter,” Ziemkiewicz said. “We’re at the stage now of constructing the field unit to go out on site next month (July).
The oil and gas industry requires a treatment system with minimal operation and maintenance, occupies a small footprint and can easily be moved from site to site.
The mobile filter unit meets these criteria and will be moved to a well site in West Virginia in July; testing will proceed for three months.
Water from similar wells was used to test the FilterSure unit in the laboratory.
“A lot of people are focusing on taking out dissolved solids,” Ziemkiewicz said. “When we started looking at frack water, produced water returns from the oil and gas industry, we came up with the need to take out suspended solids – to recycle the water, the most important thing is to take out the solid particles.
“The FilterSure unit captures all particles larger than three microns; at that point there’s no problem with plugging,” he noted. “You can run it at a high volume, low maintenance mode at the well site.
“Only about 20 percent of the water comes back out after injection, so you’re diluting the next cycle by a factor of five,” he continued.
“The dilution factor takes down a lot of the dissolved solids to acceptable levels for recycling, while the filter takes out things left in suspension, such as clays and silt particles for example.”
Benefits?
The prototype unit, which will be taken to the well, is a full-scale field unit. It can be run at 150 gallons per minute in low maintenance mode at the well site.
The successful development of a technology for treatment and reuse of RFW is slated to advance shale gas development via improved economics and resolution of environmental impacts, according to Ziemkiewicz.
“Improved economics will be achieved principally by reducing the amount of trucking and disposal of RFW and costs associated with these activities,” he said. “By reusing the RFW for subsequent fractures, the need for fresh water will be reduced.
“The better you treat the RFW, the higher the blend ratio with fresh water, the less dependence and strain on local water resources,” he emphasized, “and the less impact on local infrastructure and surrounding environment.”