Technologies May Ease Frac-Related Water Concerns June 26, 2006, New Technology Magazine
Category: Archived News Published on 2006-06-29 [Daily News] With an ever-increasing share of Western Canada’s natural gas supply coming from low-permeability reservoirs, there is a growing need for fracture stimulations.
This means a greater need for fresh water to mix frac fluids and increased costs related to disposal of used frac water. Also, there is growing uneasiness about the impact of shallow frac jobs on nearby oil and water wells, but there’s no wholly satisfactory way of modelling the impact of shallow frac treatments. … Fracturing typically requires 20 to 25 cubic metres of water per zone. With producers typically fracing multiple zones in each well drilled, the average fresh water use is estimated at 100 to 150 cubic metres per well, said Fulton. About 5,000 to 7,000 wells were drilled in southeastern Alberta and southwestern Saskatchewan each year from 2001 to 2005. The estimated water consumption is about one million cubic metres per year. Common water sources include municipal supplies, irrigation canals and other fresh-water bodies. Fulton said essentially all water used for shallow-gas well fracturing is withdrawn from the South Saskatchewan River Basin, where water allocations are being closely scrutinized. While water consumption for fracing might not be a big part of the overall picture, Fulton pointed out it is occurring in an area where water resources are already over-allocated. Some of the water used in frac jobs stays in the formation and the rest is trucked to disposal wells. “Every drop of fresh water that went into that [frac] fluid is lost to the water cycle,” said Fulton. He said the total cost of water supply and disposal is enough to justify recycling. Based on the results of a 2004 market study, Newalta built and operated a frac water recycling pilot plant at Brooks last year. Newalta’s process consists of chemical preconditioning, followed by a two-stage membrane treatment. About 1 000 cubic metres of frac water from five producers was processed over five months. The pilot project showed that 80-85% of frac water now trucked to disposal wells can be recovered to use in other frac jobs. Fulton said this would reduce fresh water consumption for well stimulation by more than 40%, and reduce wastewater injection into disposal wells by over 80%. Newalta is now looking for opportunities for full-scale field trials, which would demonstrate fluid performance economics and the ability to integrate the process into the logistics of completions and stimulations in the field. … “Water availability is now a constraint to well completions,” and disposal options are also declining, said Patrick Horner, an Aqua Pure process engineer, referring to the Barnett bottleneck. …
Besides cost and logistical concerns for producers whose wells are being fraced, there are questions about the impact of shallow frac treatments on nearby water and hydrocarbon wells. The Alberta Energy and Utilities Board recently announced new pre-fracturing reporting requirements and restrictions on shallow fracturing near water wells. These steps were taken following incidents where shallow fracturing operations affected nearby oilfield wells, according to Pat McLellan, president of Advanced Geotechnology Inc. While there are several ways of modelling frac treatments, McLellan said there is no proven, calibrated model or numerical simulator with a history of successful predictability for shallow CBM, shale gas and tight-sands fracing. “We do not have a robust design process to confidently predict the size, shape and growth rate of the stimulated zone as a function of pressure, injection rate and time,” McLellan said about shallow fracing. To improve the design process for shallow fracture stimulations — and to reduce the risk of affecting shallow groundwater and hydrocarbon zones — Advanced Geotechnology is spearheading a joint industry research project. The project just got off the ground, but new participants are still welcome, said McLellan. The goal of the joint industry project is to develop a design process and predictive tools or models for engineering frac jobs at depths of less than 600 metres in CBM, shale gas and sandstone reservoirs. McLellan said the aim is to reduce the economic and environmental risks associated with inefficient well stimulation treatment, design and implementation. The first phase of the project is to review existing research, analyze recent Alberta incidents, critique modelling options and develop and test an analytical and/or numerical model. McLellan said the second phase — which will be determined at the end of phase one — could include simulator development, expanding existing commercial tools, a field trial with an operator or commercialization through one or more service companies. [Emphasis added]