Numerical and analytical modelling of sandface temperature in a dry gas producing well

The oil and gas reservoir pressure response to the changes in the fluid production rate has been traditionally used to estimate the reservoir properties. Numerous analytical and numerical models have been developed to describe the transient pressure in and around a production well so as to interpret the in-well pressure measurements. Pressure Transient Analysis (PTA) is routinely used by Production and Reservoir Engineers at various stages in a wells life; initially for reservoir characterisation and, later, for well performance monitoring and (wider) reservoir surveillance. The recent application of high precision, downhole, temperature sensors has resulted in PTA being complemented by Temperature Transient Analysis (TTA). Recent TTA research has shown that comprehensive information on the state of the near-wellbore zone and fluid flow rates and composition can potentially be derived from such measurements. However, the derivation of useable TTA solutions describing the mass and energy transfer in porous media is challenging since it is necessary to simultaneously account for both the thermodynamic and the transient transfer effects. This paper reports a step in the development of a novel Temperature Transient Analysis (TTA) workflow. This is the first publication, to our knowledge, where the gas production TTA solutions, properly accounting for the compressible gas nature, are presented and discussed. A numerical model for determining sandface transient temperature in a dry gas producing well is developed. Simulations studies are run to understand the physics of transient temperature change and to make realistic assumptions to simplify the analytical model so as to derive an early-time, analytical solution. Finally, the limitations of the developed analytical solution are presented. This work is an important step towards a comprehensive PTA/TTA data analysis framework for multi-phase production wells.