Simplified Approach for Estimating Pressure and Temperature Profiles for Gas Wells: Verification With Literature Case

Abstract

Abstract Production from deep gas reservoirs is increasing. Most deep gas reservoirs contain sour gas, which restricts the use of pressure and temperature tools at deep reservoir's pressure and temperature. Few programs are available for estimating the pressure and temperature profiles of production wells in such an environment. Moreover, some of the programs use rigorous approach that depends on input data, which in many cases are not available. This has led users to sometimes, use the default input values or apply linear interpolation between downhole and surface data. These actions may give unrealistic pressure and temperature profiles, especially for compressible fluids in general and specifically for gas wells. This paper develops a simplified approach using production data to construct temperature and pressure profiles. The approach modifies the Cullender and Smith method for calculating a pressure profile, to account for heat transfer during the transport of fluid within production tubing. In the case of transient conditions, i.e., the startup of a gas well, it is shown that maximum differences between the simplified developed approach (model 2) and the more rigorous one (model 1) that requires more data are about 0.25% and 2% for the final pressure and temperature, respectively. Introduction Properties of transported fluids in pipelines or in production systems change with temperature and pressure. Temperature and pressure profiles are important to predict fluid behavior, i.e., phase change and development of new equilibrium among the different phases. Many approaches to temperature prediction are intended for a specific operation. Ramey Jr. (1972) focused on wellbore heat transmission. Chiu et al. (1991) presented a semi-analytical model to account for heat loss in deviated or horizontal wells. Alves et al. (1992) presented an approach for predicting temperature distribution in wellbores and pipelines. Hasan et al. (1994) predicted heat transfer in two-phase flow in wellbore. Romero (2005) presented an approach for discerning the temperature profile in multilateral wells. Moradi et al. (2011) demonstrated the effect of temperature profiles in deep gas wells on the pressure. This paper conducts a sensitivity study and comparison between two approaches: that of Moradi et al. (2011) for prediction of pressure drop in deep gas wells, and that of Cullender and Smith (1956). To facilitate comparison, the latter approach is modified to account for temperature.