Hydraulic fracturing in the Bakken oil reservoir on the Canadian side of the Williston basin involves a risk of connection to the overlying water bearing formations. The Bakken reservoir is a tight dolomitic siltstone which requires multiple stage hydraulic fracturing in horizontal wells to achieve economic oil production rates. Within ten to fifty meters above the Bakken reservoir there often is a higher permeability water bearing interval in the Lodgepole limestone formation. If hydraulic fractures connect to the higher permeability interval in the Lodgepole, then water production and associated handling costs would greatly increase. Any loss of fracture fluid and proppant to the Lodgepole could also reduce effective fracture length within the Bakken and subsequently lead to lower oil production rates. To minimize the potential negative impact of partial hydraulic fracture growth out of zone, several strategies have been used. Some of these strategies include reduction of pump rate, slurry volume and fluid viscosity. Minimizing fluid viscosity without significantly reducing proppant suspension can be a challenge. To address this issue, a unique synthetic polymer water based fluid system with excellent proppant suspension characteristics has been field tested. This system has a viscosity between that of linear gel and typical crosslinked systems and has a unique breaking process. This fluid system has been used in multiple Bakken wells for over one year and field production results will be reviewed to demonstrate the effectiveness of the combined strategies in reducing water/oil ratios. The impact on oil production rates will also be reviewed. The paper will furthermore outline several challenges with deployment in the field. Fracture geometry simulation will be used to demonstrate the expected sensitivity of fracture containment to fracture fluid viscosity and pump rate.

You can access this article if you purchase or spend a download.