The modern horizontal multistage well is a main contributor to the recent transformation of North American oil and gas production. The large fracturing stage volume that defines unconventional wells, crossed against the increasing numbers of stages and laterals per pad, has dramatically increased the demand for fracturing materials such as sand, friction reducers, and gelling agents, and most especially water. At the same time, operators face increasing accumulations of produced water, which presents as water cut from more mature assets. It is therefore natural to propose using produced water as mixwater for fracturing fluids in new completions, but in practice this plan has met with two major barriers: first, regulatory and logistical hurdles concerning the storage, handling, and potential environmental impacts of the volume of produced water required to complete a modern well (millions of gallons per lateral), and second, technology gaps in the applied chemistry of completion fluids, particularly in crosslinked gels.
This paper reports the completion of a two-lateral well in the Williston Basin where produced water, filtered but otherwise untreated, was used throughout the slickwater and crosslinked components of about sixty hydraulic fracturing stages.
Proppant was successfully placed in all perforated zones in the Bakken and Three Forks formations, using a “hybrid” design that employed seven million gallons of water (of which 2.2 million gallons were crosslinked). Production figures for the well are satisfactory, and this is discussed in the context of fluid-related completion quality. This paper will concentrate on the development and implementation of a metal crosslinked fracturing fluid that shows excellent stability at typical Bakken conditions. We will present a comparison to conventional guar-borate systems.
The promise of this approach has many potential benefits. First, completion costs are decreased as freshwater sourcing and produced water disposal charges cancel each other. Second, far fewer truck trips are necessary to transport water. Third, the industry no longer requires fresh water sources or disposal wells where this technique is employed.