Integrated Geo-Techno-Economic Reevaluation and Appraisal of the Cuthbertson Field: Low-Footprint Waterflood in a Heavily-Depleted Reservoir

Abstract This multidisciplinary study centers around a fieldwide, integrated geo-techno-economic réévaluation and appraisal of the Cuthbertson Field, located in DeWitt County, Texas. This field has undergone primary development from the early 1990s, until its plug-and-abandonment (P&A) in 2010. Albeit heavily-depleted after a two-decade-long primary-recovery period through 13 "old fashioned" vertical wells, the reservoir still has commercially-viable, "easy oil" secondary-recovery prospects via a meticulously-optimized low-footprint waterflood program, ensuring minimal environmental disturbance. A novel fieldwide-development-optimization scheme which integrates geology, technology, and economics was used to design an improved oil recovery (IOR) strategy, optimizing decisions to maximize long-term economic returns and considering features and attributes, unique to the Cuthbertson Field. It was concluded that the best approach is drilling a horizontal well for water injection and another horizontal well for hydrocarbon production. A vertical well drilled near one of the pre-existing leases, targeting a shallower brackish-water interval, which can supply the water necessary for the waterflood program. Simulations performed using a three-dimensional (3D) reservoir model built on an industrial-grade software indicated an incremental 0.8-MMbbl added to the field’s cumulative-oil production, raising its oil-recovery factor (RF) from 12% to 28%, along with an incremental 0.4-Bscf cumulative-gas production raising the gas RF from 36% to 48%. The architecture of each of the three proposed wells was designed considering the local mud window, which was used along with key drilling parameters and the necessary surface facilities to evaluate for the IOR strategy’s total cost. The oil and gas production forecasts (flowrates and cumulative recoveries) were used to calculate the expected discounted-cashflow outputs for each of three crude-oil-and-natural-gas-price scenarios, until the projected abandonment time. Typical economic-performance yardsticks, such as the net-present value (NPV), internal rate-of-return (IROR), return-on-investment (ROI), and payout period were conservatively appraised for calculating the project’s economic limit and expected profitability for each of the three crude-oil-and-natural-gas-price scenarios.