Numerical Simulation of Enhanced Oil Recovery in the Middle Bakken and Upper Three Forks Tight Oil Reservoirs of the Williston Basin
- Fabian Oritsebemigho Iwere (Schlumberger) | Robin Noel Heim (Schlumberger) | Bilu Verghis Cherian (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Americas Unconventional Resources Conference, 5-7 June, Pittsburgh, Pennsylvania USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 1.2.3 Rock properties, 5.4.1 Waterflooding, 1.6 Drilling Operations, 5.1.1 Exploration, Development, Structural Geology, 5.2.1 Phase Behavior and PVT Measurements, 5.8.6 Naturally Fractured Reservoir, 2 Well Completion, 2.5.1 Fracture design and containment, 5.2 Reservoir Fluid Dynamics, 3 Production and Well Operations, 4.1.5 Processing Equipment, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.4 Enhanced Recovery, 2.5.2 Fracturing Materials (Fluids, Proppant), 2.2.2 Perforating, 5.5 Reservoir Simulation, 6.5.2 Water use, produced water discharge and disposal, 4.6 Natural Gas, 5.8.4 Shale Oil, 4.1.2 Separation and Treating, 5.4.2 Gas Injection Methods, 5.6.9 Production Forecasting, 5.1 Reservoir Characterisation, 5.7.2 Recovery Factors, 5.5.8 History Matching
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The United States Geologic Survey (USGS) reported in 2008 that undiscovered technically recoverable oil in the Bakken was about 3.6 billion barrels across the U.S. portion of the basin, considering recent successful application of horizontal wells and multistage hydraulic fracturing technologies. As the development of the unconventional resources in the Williston Basin continues beyond the phases of exploration and lease evaluation, optimum well spacing and recovery factor will become forefront considerations in the formulation of asset development strategies. Based on our studies the reservoir producing mechanism is primarily solution gas drive and primary oil recovery factor is lower than 15% of the original oil in-place. This low recovery or very high oil volume remaining in place is a strong motivation to investigate the application of enhanced oil recovery methods in this basin.
This paper describes the construction of numerical simulation models using typical fluid and rock properties for the Bakken and Three Forks, assuming both naturally fractured and single porosity systems and their combinations. Multistage hydraulic fracture properties are determined from well completion engineering and coupled with the flow models. The flow models are constrained by well operating practices implemented by operators across the basin during primary oil production.
The results of pressure maintenance methods to arrest the rapid reservoir pressure decline due to large pressure drawdown necessary to produce oil and water, as well as gas (including carbon dioxide) and water injection methods to improve oil recovery are presented.
The Bakken Formation in the Williston Basin has three members, namely the Upper Bakken Shale, Middle Bakken and Lower Bakken Shale. The Lodgepole overlays the Upper Bakken Shale while the Lower Bakken Shale overlays the Three Forks Formation, Figure 1. Both the Upper and Lower Bakken Shale are organic rich dark shale which are both the source and traps for the hydrocarbons. The Three Forks formation also has three members; the Upper, Middle and Lower Three Forks. All three members are highly laminated dolomite/claystone/shale sequences. The Upper Three Forks has the best reservoir quality of the three as water cut for wells completed in these zones generally increases with depth. The thickness of the Bakken and the Three Forks increases toward the center of the Basin along the Nesson Anticline. The Middle Bakken and Upper Three Forks with the best reservoir quality (porosity and oil saturation) are the primary targets for development.
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