Temperature Behavior of Geothermal Wells During Production, Injection and Shut-in Operations

Abstract

Static and dynamic measurements of pressure and temperature along geothermal wells are commonplace practices for characterization purposes in the geothermal industry. Such profiles provide good insight regarding the deliverability of the well, location of the upper and lower boundaries of the reservoir / reservoirs and etc. The static temperature profiles, for example, can be used for modeling the natural state of the system through history matching. As these profiles are taken, it is important that the actual static and dynamic conditions are reached. In other words, to take a dynamic temperature profile, one would have to wait until the temperature profile stabilizes in the well after production has started and vice versa for the static profile. Hence it becomes crucial to know beforehand how long the stabilization time takes. In this study a numerical model is developed to study the parameters effecting the stabilization time of static and dynamic conditions in the wells for a single phase water system. The model is based on mass and energy balance equations and couples the reservoir with the well and takes into account the heat losses to the surroundings of the well. The model is validated using various analytical models in the literature. A synthetic application is provided to identify key parameters that effect temperature distributions. In the application we model temperature behavior along the well for the transition from static to dynamic and from dynamic to static.