Abstract
The estimation of reserves and performance prediction are two vital tasks for the development of gas reservoirs where the evaluation of gas in place or well-controlled reserves, as the foundation of the performance analysis of gas wells, turns to be exceedingly significant. Advanced production data analysis or modern rate transient analysis (RTA) methods mainly depend on the iterative calculations of material balance quasitime (tca) and type curve fitting, the essence of which is to update the average reservoir pressure data time and again. The traditional Arps’ decline models are of empirical nature despite the convenience and applicability to the constant bottomhole pressure (BHP) condition. In order to avoid the implicit iteration, this paper develops an explicit method for estimating the average reservoir pressure on the basis of dynamic material balance equation (DMBE), termed “flow integral method,” which can be applied to various gas production systems under boundary-dominated flow (BDF). Based on the flow integral method and the decline parameter evaluation, we employ the hyperbolic decline model to model the gas well performance at a constant BHP. The analytical formulations of decline rate and decline exponent are deduced from the DMBE and the static material balance equation (SMBE) considering the elastic compressibilities of rock pore and bound water. The resulting decline parameter method for explicit estimation of gas reserves boasts a solid and rigorous theory foundation that production rate, decline rate, and average reservoir pressure profiles have reference to each other, and its implementation steps are explained in the paper. The SMBE can, combined with the estimated pressure profile by the flow integral method, also be used to determine gas reserves which is not limited to the constant-BHP condition and can calibrate the estimates of the decline parameter method. The proposed methods are proven effective and reliable with several numerical cases at different BHPs and a field example.
Highlights
The production performance analysis of gas wells runs through the gas reservoir development
Equation (35) reveals that gas reserves can be estimated according to the intrinsic relationship between production rate, decline rate, and average reservoir pressure, but it needs to know the relation of formation pressure to time
(4) The production data matching in the decline parameter method could be superior to the analytic calculations of qi, decline rate (Di), and na in the modified Stumpf method based on the straight line of q1−na vs. gas production (Gp) which is only suitable for early boundarydominated flow (BDF) data
Summary
The production performance analysis of gas wells runs through the gas reservoir development. The density function, in reality, ignores the viscosity term in pseudopressure, while the treatment of pseudotime factor is consistent with the traditional definition of pseudotime They evade the iteration of gas reserves for the first time and use the coincidence of liquid solution and numerical simulation results (or gas well data) in the early stage when changes in gas properties are not obvious to select the dimensionless reservoir radius in liquid-type curves, and the differences during BDF are employed to determine the λ and β profiles. The static material balance equation is introduced to deduce the analytic expressions of decline rate and decline exponent; we explain the rationales behind the traditional hyperbolic model to characterize the production decline data of constant-BHP gas well and the fundamentals of the decline parameter method available for reserve estimation. The innovations of the article are outlined and the conclusions are drawn
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
