Performance Evaluation of Horizontal and Multilateral Wells, Steelman Frobisher Beds Pool: A Probabilistic Quick-Look Approach

In mature fields such as the Steelman Frobisher Beds Pool wherein terminal oil production decline from existing legacy vertical oil wells had long begun, operators are constantly looking for innovative ways to increase productivity, optimize recovery, and reduce environmental impacts. Horizontal (HZ) and multilateral (ML) wells can help achieve these goals. Generally, HZ wells have proved viable in developing thin-pay reservoir horizons and management of reservoirs with bottom-water. The need to improve reservoir contact, accelerate oil production, and reduce surface footprint of drilling operations has driven the deployment of ML wells. To foster increased deployment of ML wells in Saskatchewan and in line with the province’s goal to increase production to 600,000 barrels of oil per day (bopd) by 2030, the Government of Saskatchewan introduced the MLWP (Multi-Lateral Oil Well Program) effective April 2024.

The Steelman Frobisher Beds Pool was discovered upon drilling and testing of the Frobisher Beds via the 101/09-34-003-04W2/00 (License Number: 54B013) well. Oil production from the pool began in March 1954. The main productive reservoir targets within the Frobisher Beds comprises of the generally tight, argillaceous cryptocrystalline-dolomite and lime-mudstone interval of the Frobisher Marly/” State A” and the compartmentalized Frobisher Vuggy (mainly the Huntoon/Bluell and Griffin/Sherwood) interval. Most of the recently-drilled ML wells target multiple horizons/benches. As of year-end December 2024, reported cumulative oil production (Unit plus Non-Unit) from the pool was 7,256,311 m3, or R.F. (recovery factor) of ~10 % of estimated OOIP (original oil-in-place). Hence, based on the remaining OIP (oil-in-place), the upside potential in terms of improved oil recovery opportunities is significant.

A quick-look probabilistic approach was utilized to analyze the performance of HZ and ML wells (403 wells with a total of 728 laterals) completed within the Steelman Frobisher Beds Pool. Using actual production data, the distribution of selected parameters [IP 90 oil (initial production, oil, within the first 90 days onstream), IP90 produced water and EUR (estimated ultimate recovery), respectively] was generated. P10, P50 and P90 estimates of IP90 oil for HZ and ML wells were calculated as 3,351 m3; 1,392 m3 and 213 m3 compared to 949 m3, 295 m3 and 20 m3 for non-HZ wells. Individual PDP (Proved Developed Producing) reserves for 56 HZ and ML wells drilled between January 2023 and August 2024 were forecasted; “best estimate” EUR values for P10, P50 and P90 are 8x103 m3, 30x103 m3 and 101x103 m3, respectively. For comparative purposes, the P10, P50 and P90 estimates of the EUR of 403 legacy vertical wells were calculated as 41,294 m3; 4,503 m3; and 33 m3, respectively. The EUR values can be used as a basis for PUD (proved undeveloped) reserves in future development planning within the pool. The generated distributions also provide a basis for estimating some valuation metrics, scheduling accretion and benchmarking EUR estimates from decline curve analyses or other type well method. Nonetheless, pool-wide cumulative recovery is 10% OOIP. Hence, the results warrant an investigation into options for optimal (re)completion and reservoir depletion strategies (including infill drilling/modified well spacing, waterflood, IOR (improved oil recovery) and reservoir management). Some implications of focusing on increasing IP (initial production) rates versus EUR via HZ and ML wells are also highlighted.