Well Completion Strategy and Optimization in a North Dakota Bakken Oilfield
- Dennis Michael Zander (Fidelity E&P Co.) | Rocky Allen Seale (Packers Plus) | Daniel Snyder (Packers Plus)
- Document ID
- Society of Petroleum Engineers
- SPE Middle East Unconventional Gas Conference and Exhibition, 31 January-2 February, Muscat, Oman
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 1.8 Formation Damage, 2.5.2 Fracturing Materials (Fluids, Proppant), 2 Well completion, 5.8.2 Shale Gas, 5.1.5 Geologic Modeling, 1.6 Drilling Operations, 5.8.4 Shale Oil, 5.1.1 Exploration, Development, Structural Geology, 1.10 Drilling Equipment, 4.6 Natural Gas, 2.2.2 Perforating, 2.5.4 Multistage Fracturing, 1.6.6 Directional Drilling
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First discovered in 1951, development of the Bakken formation in the Williston Basin has been problematic and inconsistent. However, technological advancements in horizontal drilling and completions in the past decade have steadily improved production results and consistency on a well by well basis. So much so, that the United States Geologic Survey (USGS) reported in 2008 that the undiscovered, technically recoverable oil in the Bakken was between 3 to 4.3 billion barrels.
How many fracture stages to run and how far apart to space stages in horizontal wells are prevalent questions asked by the oil and gas industry. This study provides insight into the advantages of various stage numbers and optimum stage spacing by analyzing up to 21 months of production results from horizontal wells targeting the Bakken in the Stanley Field, North Dakota. These wells were completed with open hole, mechanical systems (OHMS) and production is compared to offset wells and field averages.
Advancements in OHMS completion and fracturing technology have enabled maximized production from this asset. The lessons learned and methodology can be utilized for other unconventional oil and gas plays around the world.
Description of the Bakken. The Bakken Formation dates back to the late Devonian to early Mississippian Age and covers about 200,000 square miles of the Williston Basin, which is located in Montana, North Dakota, Manitoba, and Saskatchewan (Figure 1). It is the largest onshore sedimentary basin in the United States (Pollastro et al., 2008).
Bakken oil was first discovered in 1951 but it was not until the 1970s that the Bakken formation was recognized as a potentially large oil and gas reserve. In recent years, advancements in horizontal drilling have made it possible to demonstrate technologically and economically recoverable reserves. Currently, Bakken reserves are estimated at 3.65 billion barrels of oil, 1.85 trillion cubic feet of gas, and 148 million barrels of natural gas liquids; and reserves are growing larger as technology advances (Pollastro et al., 2008).
The Bakken formation is made up of three members. The Upper and Lower members are organic-rich shales that provide the source of, and trap for, the hydrocarbons in the the Middle member (Figure 2) (Pitman et al., 2001). A mix of dolomite, siltstone and sandstone, the Middle member has both low porosity and permeability values, averaging 5% and 0.04 mD, respectively (Pitman et al., 2001). However, higher porosity and permeability values are associated with natural fractures, which contribute to the ability to recover reserves (Pitman et al., 2001; Olsen et al., 2009). In the study area, the Bakken target is at a depth of between 9,500 and 10,500 ft. and can reach up to 135 ft. thick (Powell, et al., 2007).
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