Abstract
The presented study focuses on the Permian Delaware Basin Wolfcamp A (WCA) formation with the objectives: 1) to understand how completion practices and geology influence the productivity of existing wells using machine learning technique and state-of-art model explainer - SHapley Additive exPlanations (SHAP); 2) to predict the EUR of future wells and assess the technically recoverable oil in a focus study area (5,000 sq. mi, ~40% of the Delaware Basin by area) of Delaware WCA formation. Our results show that hydraulic fracturing water use intensity (HFI), true vertical depth, lateral length, sandstone facies, and formation thickness are the top five variables driving the first year productivity (stb/1000ft). For the existing producing wells in the AOI, median EUR using multi-segmental Arps model is ~30% higher than median EUR using the physics-based model (475 thousand barrels (Mstb) vs. 320 Mstb) and such differences decrease as the observed production period increases, indicating the large uncertainty that decline curve analysis will bring to EUR estimation for both existing wells and future wells. Our predictive and technically recoverable resource analyses assume that future wells will be drilled under the current technology in terms of lateral length, HF water use, proppant use, and well spacing. Based on the first year productivity analysis and the average decline curves predicted by Arps and physics-based model, the expected EUR of future wells in the AOI ranges from 140 Mstb to 780 Mstb. The technically recoverable oil in the AOI is in range between 10 billion barrel (Bstb) to 22 Bstb and the corresponding area wide recovery factor is in a range between 9% and 19%.
Production of oil and natural gas from U.S. unconventional resources has soared in recent years with the Permian becoming the largest producing basin. The Permian Basin is less mature compared to other unconventional plays in the U.S., such as Bakken and Eagle Ford plays, in part due to the vast size of the area, thickness of organic-rich deposits and multiple economic targets. In 2019, oil production from the Permian Basin accounted for ~35 percent of the total U.S. crude oil production and ~15% percent of total U.S. natural gas production (EIA, 2019a, 2019b). While production is expected to slump in 2020, the recent high rate of oil and gas production from the Permian raises the question: how long can recent production rates be maintained, irrespective of changing oil prices with time? To help answer the question, we need to understand what factors influence production. With that understanding, and by developing an understanding of the remaining inventory, we can better forecast future production in the undeveloped area of the basin and develop a view of remaining potential.
