Case Study: Industry Partnership Defines Fracture Completion Best Practices in North Dakota Bakken Play

Bakken Research Consortium identifies key controls for economic production from unconventional oil reservoirs

Challenge: Unravel geological and geomechanical factors that affect fracture initiation and propagation in the Middle Bakken and Three Forks plays, using best-in-class technologies.

Solution: Drilled three parallel laterals; ran high-end logs to characterize reservoirs; compared single-stage fracture completion in one lateral with multistage frac in another.

Result: Documented effective multistage completion techniques, which have become common practice since 2008 and boosted oil production and estimated ultimate recoveries.

Understanding reservoir complexities, completion strategies

After several years of successful drilling and completion of horizontal wells on the Montana side of the Williston Basin, operators began seriously exploring the North Dakota Bakken play in 2006. Although the Bakken is more extensive in North Dakota, it is also more lithologically heterogeneous.

Initially, the industry did not fully understand reservoir complexities or optimal hydraulic fracture completion strategies. It was common at the time to run a perforated liner and try to fracture-stimulate the entire lateral in one continuous stage. But results were disappointing, production was inconsistent, and North Dakota Bakken development lagged behind that of Montana.

Operators experimented with various drilling and completion technologies and fracture fluids, but each new player’s learning curve in this exciting new oil resource proved long, expensive, and redundant. The key challenge was to better understand and control fracture initiation and propagation in the Middle Bakken and Three Forks formations.

Identifying factors affecting hydraulic fracture stimulation

In the fall of 2007, the Bakken Research Consortium was formed by Schlumberger petrotechnical services as the primary technical partner and project leader, with seven operators and three other technical contributors, including the US Department of Energy. The consortium also received a grant from the North Dakota Oil and Gas Research Council.

The objective was to apply best-in-class technologies to improve understanding of the geological, drilling, and completion principles necessary to optimize production. The study area is on the eastern flank of the Nesson anticline in Williams County, North Dakota. A vertical pilot hole and three horizontal wells were drilled 1,500 ft apart in early 2008.

A high-end log suite was run to fully characterize matrix mineralogy, porosity, permeability, mechanical properties, and stress states. The central lateral was cored, and a downhole geophone string was installed to monitor microseismic events caused by hydraulic fracture stimulation of the two outside laterals. One was completed in a single stage with a preperforated liner—the current industry practice. The other was completed with swell packers, a blank liner, and six plug-and-perf frac stages using a hybrid fluid design. Chemical and radioactive tracers were used to tag frac fluids and proppants for each stage.

Developing industry completion best practices, boosting oil production

Multidisciplinary analysis, modeling, and simulation found that stress variations within the lateral impact fracture initiation, and fluid type coupled with a clear understanding of rock properties affects fracture height growth. Because of significant variations in reservoir lithology, proper well placement is essential in this play. Most important, the team demonstrated unequivocally that multistage completions provide better fracture stimulation than a single-stage completion.

Consortium members immediately used these findings to optimize their completion strategies. Today, completions with an increasing number of fracture stages are common. According to the North Dakota Department of Minerals, significant increases in estimated ultimate recovery (EUR) and oil production rates over the past few years are primarily a result of the introduction of multistage fracturing in 2008.

One consortium operator, for example, completed its first 12-stage fracture job of a short lateral in late 2008. This change increased EUR relative to single-stage completions by more than 284,000 bbl. By November 2010, the company had drilled 39 consecutive long-lateral Bakken and Three Forks wells in North Dakota, with up to 38 fracture stimulation stages, producing an average of 2,777 bbl over the first 24 hours of operation.

Download: Industry Partnership Defines Fracture Completion Best Practices in North Dakota Bakken Play (2.15 MB PDF)

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Schlumberger DCS and industry partners studied three horizontal wells in the North Dakota BakkenDrainage boundary based on microseismic (gray) with hydraulic fracture patterns.North Dakota Bakken production
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