Alaska's Next Mega Field: Leveraging Unconventional Simulation Workflows for Conceptual Field Development

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Abstract Along Alaska's North Slope, an operator has discovered multi-billion barrels of resources in proven oil-bearing reservoirs. A joint project with an energy services company aims to leverage integrated unconventional workflows, including horizontal well planning, hydraulic fracturing design, and comprehensive geological and reservoir modeling, to develop a conceptual field development plan for one of the reservoirs. This will facilitate the exploitation in the Ahpun area, near the Trans-Alaska Pipeline and Dalton Highway, ideal for year-round phased development. The unique geology of this tight oil reservoir required an unconventional workflow for the field development plan. Seismic interpretation was conducted to define horizons and attributes for reservoir facies and properties. Log analysis was performed for porosity, water saturation, and sonic data, along with geomechanics for elastic rock properties. Hydraulic fracture modeling and sector reservoir simulation were used for history matching, well spacing evaluation, and production forecasting. An uncertainty analysis was carried out to derive P10/P50/P90 production ranges based on the uncertainty of reservoir properties and fracture geometry. A rig schedule and pad drilling plan was developed to scale the production forecast for the development area. A 26-million-cell 3D static model covering 740 square miles was constructed using seismic horizons, well tops, and petrophysical logs. Secondary data conditioning to seismic attribute volumes improved property models away from well data. Hydraulic fracture modeling and production history matching for one horizontal well showed relatively low cluster efficiency and a smaller effective half-length. Improved fracture design was proposed which incorporates limited entry techniques, larger proppant volume, and managed flowback to improve cluster efficiency and effective fracture half length. Well spacing sensitivity cases evaluated estimated ultimate recovery (EUR) from 1 to 15 wells per section. EUR per well deviated from the plateau, starting at eight wells per section. With a 660-ft well spacing, the P50 EUR per well for 10,000-ft lateral length was estimated at 0.47 MMSTB oil, 8.3 BCF gas, and 0.83 MMSTB NGL, totaling 1.3 MMSTB liquids. Oil recovery per section was projected at 8%, with gas recovery at 44%. Uncertainty analysis highlighted that fracture geometry and water saturation are key factors influencing the EUR estimate. Fluid uncertainty affects gas production and gas-oil-ratio trend with free gas coming out of solution. The P10/P50/P90 production forecast profile was projected with a rig schedule and pad drilling plan for the full field in the Ahpun West Alkaid reservoir. This work applied the unconventional workflow and techniques to the development of tight oil fields in Alaska. Comprehensive reservoir modeling was performed with the integration of domain expertise, including geophysics, petrophysics, geology, stimulation, and reservoir engineering. The results highlight the conceptual field development plan for the Ahpun West Alkaid reservoir, offering valuable insights and a reference for future oil development in similar tight oil fields in Alaska.

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