Analysis of Decline Curves on the Basis of Beta-Derivative

Abstract

Summary This paper presents a new simplified method for forecasting oil and gas production during transient and boundary-dominated flow (BDF), which does not require the use of complex analytical or numerical modeling tools. The method is based on the behavior of the beta-derivative (β), where two approximate straight lines are obtained during transient flow and BDF with slopes mt and mb, respectively. The method is applicable not only to vertical wells in conventional reservoirs producing during BDF but also to hydraulically fractured vertical/multifractured horizontal wells in unconventional reservoirs with prevailing transient (linear) flow. Upon selection of an appropriate βBDF—which mainly depends on the type of flow regime (i.e., radial or linear)—and using the proposed equations, type curves can be generated that provide a convenient method for obtaining the slopes of beta-derivatives for transient flow (mt) and BDF (mb) through a type-curve matching process. The method is validated by comparing results against oil and gas numerical simulations of vertical and hydraulically fractured vertical wells. The developed method is not biased toward any flow regime or presence of skin. Flow regime and skin effects are embedded in the βBDF and mt parameters. Transient flow and BDF are accounted for through the slopes mt and mb, respectively. Corroborated with the use of numerical simulation and field data from the Western Canada Sedimentary Basin and Mexico, the proposed method provides reliable production-rate forecasting while staying away from the complexities of analytical or numerical modeling.