As companies seek to minimize costs in their hydraulic fracturing operations, they must examine the methods they employ to handle, treat, and use produced water and freshwater sources. In a presentation held at the 2016 Unconventional Resources Technology Conference, Barry Donaldson, vice president of global sales and marketing at Tetra Technologies, discussed possible cost-effective water management strategies.
Donaldson’s presentation, “Simple, Environmentally Friendly, and Economical Methods to Maximize the Reuse of Produced Water for Frac Operations,” focused on infrastructure planning. He said operators must consider building water storage and treatment facilities on-site along with their production facilities, taking into account the volume of water that may need to be injected over the life of the field.
By anticipating the total water volume, the location of each fracture, and the type of fracture, operators can better determine the quality of water and the treatment needed to support their operations. A central gathering facility for produced water may lower operational costs.
“You need to consider, just like you would with your production facilities, how you’re going to get your water, where you’re going to put it, and does it need to be central to where your operations are going to be over the life of the well,” Donaldson said. “Instead of having to go to tanks and trucking it somewhere, just put it in the infrastructure to move it to a specific location where you can store it and then, on top of that, is there a treatment strategy that you can develop into that infrastructure plan.”
The primary objectives for water treatment are to produce an environmentally friendly, cost-effective fluid that is clean enough for downhole use. To achieve those ends, Donaldson highlighted three types of commonly used techniques to blend fresh water and produced water.
Batch processing, the natural mixing of predetermined volumes of fresh water and produced water in a storage tank, must be performed prior to injection. Donaldson said the lack of real-time mixing may add to treatment costs, and by not stimulating the mixing process, the water may stratify in the tank after a certain period of time. Volumetric blending involves the simultaneous pumping and injection of fresh and produced water. This allows for real-time mixing, preventing possible stratification, but the output quality of the mixed water is not as easy to control.
“You pump those volumes and hope the input quality and output quality stay the same. It’s real time, but the water variations from the input and output aren’t controlled, so you’re going to have more variation as you pump that water,” Donaldson said.
A parameter-controlled blending process involves the measurement of the input quality of fresh water and produced water and the use of an automated system that adjusts the output volumes based in real time to ensure a consistent water mixture during injection. Though real-time monitoring and automation may add more cost on the front end, Donaldson said this process is optimal for companies willing to invest in the necessary infrastructure.