Near wellbore thermal effects in a tight gas reservoir: Impact of different reservoir and fluid parameters

Temperature changes in and around the wellbore could lead to significant well performance and flow assurance issues. Despite its importance, near wellbore temperature change due to gas production and its importance on well performance is not well understood. Reduction of temperature in the near well bore section, could potentially lead to hydrate formation and as a result reduction of well performance.

This work is aimed at evaluating the thermal behaviour in the near wellbore region of a low to tight permeability gas reservoir (ranging between 0.02 and 10 mD) during its natural depletion. The study is conducted by using a thermal-compositional simulator. The process required to simulate such thermal behaviour in a numerical simulator is outlined in this paper. This study is focused on analysing the impacts of different parameters such as reservoir and fluid properties, well trajectories and draw down magnitudes have been studied. Such parameters have an impact on JTE or conductive/convective heat transfer and therefore will affect the reservoir temperature. In addition the near wellbore temperature responses to varying production and well configurations are reviewed to identify the contributing parameter and their impact on reservoir temperature.

The results of a grid sensitivity analysis showed that the choice of grid size will have a significant impact on calculated temperatures. In addition, the results reveal that significant temperature reduction could occur around the wellbore due to Joule-Thomson expansion and heat transfer in form of conduction and convention. It is also shown that size of the affected area depends on the magnitude of cooling due to Joule-Thomson expansion as well as reservoir properties such as skin and permeability. This study showed that the most influential parameter is the wellbore inflow rate due to draw down. In addition, parameters such as pressure profile along the well trajectory, inflow area along the well and reservoir quality along the wellbore will play a vital role in cooling process as well as radius of the impacted zone. The results also showed that absolute initial reservoir temperature have no significant impact on the magnitude of temperature change.