Temperature transient analysis has been evolved as a new alternative that can be adopted jointly with pressure transient analysis for reservoir characterization and surveillance purposes. In this work, an analytical approach is developed to characterize the reservoir using down-hole temperature measurements obtained during a pause in injection activity. The analytical solution is developed by solving mass conservation equation coupled with energy balance equation, which are subject to appropriate initial and boundary conditions. The solution is obtained using Hankel integral transformation to evaluate the temperature response with respect to time and space. The obtained solution identifies and evaluate: (i) the early-time cooling effect caused by adiabatic expansion of injected fluid in injection zone after injection stops and, (ii) late-time warm-back effect caused by heat flux from cooled unswept region and the surrounding cap/bed strata. Using early- and late-time asymptotic solutions, temperature inversion procedures are introduced in the form of appropriate graphical techniques to characterize the reservoir. Measured sandface temperature after injection is stopped along with the developed procedure are used for evaluating thermal properties of reservoir such as effective heat capacity and thermal conductivity, pressure diffusivity of the reservoir, extent of thermal front and initial geothermal reservoir temperature. The analytical solution results are validated against numerical results obtained via a thermally coupled numerical reservoir simulator. The analytical solution provides good agreement with the numerical results during forward modelling and inverse modelling. Sensitivity analysis is developed to investigate effect of wellbore storage, characteristics of reservoir and injection rate on the temperature behavior during shut-in.

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