Improving Well Productivity and Profitability in the Bakken--A Summary of Our Experiences Drilling, Stimulating, and Operating Horizontal Wells

Abstract

fax 01-972-952-9435. AbstractThis case study will summarize the lessons learned during the stimulation and operation of horizontal laterals completed in the Middle Bakken formation of North Dakota and Montana. This paper will compare the production histories of these wells to offset wells completed with other techniques to evaluate best industry practices. Insight will be shared as to the effect of lateral length, wellbore azimuth and stimulation design on well production and overall well economics.The Bakken formation of the Williston Basin is undergoing significant development in Manitoba, Saskatchewan, Montana, and North Dakota. Numerous operators are active in the area, with a wide variety of development approaches. The industry has not yet reached consensus on optimal drilling and stimulation strategies.Results indicate significant progress in improving well production, while reducing the drilled lateral length and the treatment size. Efforts to improve diversion and optimize proppant type and size appear to provide more effective fracture treatments, while eliminating production problems related to the flowback of frac sand. This paper will provide the following benefits to readers:• Operators in the Bakken have experienced significant problems with flowback of frac sand, requiring frequent pump changes, conservative production strategies, and expensive cleanouts prior to restimulation. This paper will describe the steps taken to eliminate proppant flowback into the wellbore and the estimated economic impact.• This paper will provide a case study comparing the production from wells completed with a variety of strategies. • The results suggest many current laterals drilled in the Bakken are ineffectively stimulated and demonstrate that significant increases in well profitability are possible with more optimized treatments. • Optimizing fracture treatment designs for horizontal wells requires an estimation of the fracture geometryparticularly a description of the intersection between the wellbore and the fracture. A fracture treatment designed under the assumption of a longitudinal frac will be entirely inadequate if the actual fracture propagates in a transverse orientation. This paper will describe our understanding of the fracture geometry and how that has affected treatment designs.

Improved Production and Profitability Achieved with Superior Completions in Horizontal Wells: A Bakken/Three Forks Case History

“…In the Middle Bakken, there is evidence that hydraulic fracture treatments have broken into offset wells from the treated well, pumping sandladen crosslinked slurry to surface [Wiley 2004, Eberhard 2005, Besler 2007]. This observation confirms that in some locations, creation of very long transverse fracs occurs, and that these fractures can exhibit surprisingly good containment within the Middle Bakken interval.…”

“…This N-S orientation is believed to be in the approximate direction of the minimum horizontal stress, which facilitates the initiation of multiple transverse fractures from the wellbore [Besler 2007]. Although some early modeling studies predicted that a single longitudinal fracture could achieve equivalent production from the Bakken [Wiley 2004], most operators have found advantages in creation of multiple transverse fracs as they provide superior rates and improved ultimate recoveries.…”

“…Transverse fracs can provide an excellent way to efficiently contact the reservoir, however at the intersection of the created transverse fracture and the wellbore, high fluid velocities are experienced which lead to large pressure losses in the propped fracture [Shah 2010]. As previously discussed by Dedurin (2006) and Besler (2007), oil velocity in a transverse fracture can exceed one million times the oil velocity in the formation. This operator offsets these high velocities and pressure losses with higher quality proppant, higher proppant concentrations near wellbore, and the creation of more hydrocarbon entry points.…”

“…There are numerous field examples in which ceramic proppant provided far superior production and total recovery of reserves than lower quality proppants [Vincent 2009]. Field studies in the Bakken [Besler 2007] and in the Pinedale [Huckabee 2005 andVincent 2007] have shown a low density ceramic to outperform a broadly sieved intermediate density ceramic (IDC) when utilized at depths of 10,000 to 12,000 ft TVD. This benefit is partially due to the 20% greater volume provided by a similar mass of a low density ceramic, and partially due to more uniform particle size.…”

“…This operator has also exclusively utilized ceramic proppant which is more resistant to crushing under drawdown. Many operators using frac sand in the Bakken have reported extensive problems with flowback of frac sand [Besler 2007] and some operators report that more than 300,000 lbs of sand must be cleaned from laterals prior to restimulation. In some Bakken wells completed with frac sand, as much as 50% of the original proppant has been subsequently removed from the wellbore in repeated cleanouts.…”