Water and Hydrocarbon Production in the Upper Wolfcamp Formation: Insights from Simplified Flow Models

Substantial water production associated with oil production in unconventional plays presents a challenge for the sustainable development of oil and gas resources. Recent studies have identified the origin and content of water in these unconventional formations, such as the Wolfcamp in the Delaware Basin, West Texas, but little is known regarding the mechanisms and drainage pathways through which water is produced. Understanding these mechanisms is crucial for water control and sustainable unconventional resources development. In this study, we explore whether simplified conceptual flow models can effectively capture the formation’s characteristics and reproduce production history. We first collected water production data from over 8000 wells in the upper Wolfcamp Formation of the Delaware Basin. We then hypothesize that either (a) water and oil are produced simultaneously from each layer or (b) water is produced from water-bearing layers and oil from oil-bearing layers. To test these hypotheses, we develop simplified models for both cases and predict production behavior from various model versions, incorporating different wettabilities and capillary pressures, and the presence or absence of crossflow of the models. Our findings indicate that the heterogeneous multilayer segregated flow model matches the majority of observed field water cut data. The results show that water being produced from water-bearing layers and oil from oil-bearing layers is the most plausible explanation for water and oil production in the high water cut upper Wolfcamp Formation of the Delaware Basin. Furthermore, the results suggest that crossflow between layers significantly affects oil production, with its effect depending on the ratio of the fracture height to fracture spacing. These insights contribute to the sustainable development of unconventional oil resources by identifying water sourcing, optimizing production strategies, and improving water management.