Water. desalination + reuse

TECHNOLOGY Recycling Flowback and Produced Water in Tight-Oil Development _________ Roberta Wasylishen, president, RW Project Consulting Inc, Canada, ___ Editor's Note: One of the most lively presentations at the recent International Desalination Association conference in Banff, Canada, came from local consultant Roberta Wasylishen, who described what is was like for a water engineer to get access to oil & gas projects in order to do a water treatment assessment. This article is based on her investigation and includes information on frac, flowback and produced water. TECHNOLOGICAL ADVANCES in horizontal drilling and multi-stage hydraulic fracturing are the primary mechanisms facilitating tight-oil (shale oil) production within low permeability reservoirs throughout the Western Canada Sedimentary Basin (WCSB) 1. The combination of technological innovation, an improved royalty scheme within Alberta and regulatory changes permitting tighter down-spacing of wells has accelerated industry's interest in the development of tight-oil reserves 2. However, the expedited rate of tight-oil development is creating new challenges, including identifying sustainable supplies of source water for hydraulic fracturing and management of water-based hydraulic fracturing flowback fluids. Recycling flowback can offset hydraulic fracturing fresh water requirements while avoiding the cost associated with flowback disposal. Despite the potential socioeconomic and cost-saving benefits, the Canadian Petroleum Producers Association (CAPP) documented that in 2011 only 5% of water-based flowback fluids were being recycled to support shale-gas, tight-gas and tight-oil hydraulic fracturing activities throughout Western Canada 3. In an effort to improve these metrics, Penn West Exploration in support of the Petroleum Alliance of Canada (PTAC) initiated a research study in 2011. The project included four primary objectives: l l l Assessment of reuse opportunity potential for hydraulic fracturing in tight oil Establish desired water quality guidelines needed to support reuse initiatives Characterization of fresh water (frac water), flowback and produced waters Development of a baseline treatment methodology. The research is primarily intended to bridge the information gap between operators and water treatment technology vendors on what is important, why it is important and how we can approach flowback and produced water reuse opportunities in tight-oil developments. l HydRaulic FRactuRing OveRvieW The purpose of hydraulic fracturing is to increase the exposed production flow area of the formation by pumping a pressurized fluid into the well to produce narrow cracks (fractures). These fractures serve as channels within the formation to permit flow of the trapped hydrocarbons to the wellbore 4, page 6. This may be achieved by pumping a base fluid consisting of water, foam or oil containing small concentrations of chemical additives as well as proppant (sand) material. As the pressurized fluid is pumped into the well, the newly formed fractures are supported open by the proppant. Placement of the proppant into the newly formed fractures during the hydraulic fracturing stimulation facilitates enhanced permeability within the formation as the well transitions to production mode 4, page 5. Once the hydraulic fracturing stimulation is complete, a portion of the original frac fluid combined with comingled constituents from the formation water flows back to the surface where it is either treated for reuse or trucked off site for disposal. HydRaulic FRactuRing Fluid SelectiOn Selection of the base fluid for hydraulic fracturing | 26 | Desalination & Water Reuse | August-September 2013

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