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# [S24-P-03] Determination of formation equilibrium temperature from unsteady temperature measurements in wells under drilling

The temperature distribution recorded in wells corresponds to the equilibrium temperature distribution only the measurements were performed in shut-in wells. In practice the temperature measurements are usually performed in scientific, control, piezometric and idle production wells. To determine the equilibrium temperature of rocks after well drilling completion it is necessary to wait for a long time before the well reaches shut-in state that is possible in very rare cases only.

We have proposed a method of determining the equilibrium temperature of rocks from the unsteady temperature recording within some time interval in a well at drilling breaks or after drilling completion. Determination of the equilibrium temperature is based on the solution of the inverse problem using the developed simulator. The simulator allows to calculate the model temperature distribution in drilling wellbore, provides accounting for spatial variations in rock thermal properties and allows to take into account the history of parameter during the well drilling, such as drilling speed, flow rate and temperature variations of the mud at the wellhead. Recording the temperature variation T(t) in the borehole at a particular depth H versus impermeable zones after drilling completion and comparing it with the model temperature Tm(t), calculated using the simulator for different functions of the equilibrium temperature TG(H), allows to determine the equilibrium temperature of the rocks. The mathematical model developed provides modeling the temperature distribution during the drilling process. Results of the sensitivity study of the model describe the model sensitivity to the uncertainties in the input data. The calculations of the formation equilibrium temperature from the unsteady temperature data recorded in the well after the drilling completion were performed.

We have proposed a method of determining the equilibrium temperature of rocks from the unsteady temperature recording within some time interval in a well at drilling breaks or after drilling completion. Determination of the equilibrium temperature is based on the solution of the inverse problem using the developed simulator. The simulator allows to calculate the model temperature distribution in drilling wellbore, provides accounting for spatial variations in rock thermal properties and allows to take into account the history of parameter during the well drilling, such as drilling speed, flow rate and temperature variations of the mud at the wellhead. Recording the temperature variation T(t) in the borehole at a particular depth H versus impermeable zones after drilling completion and comparing it with the model temperature Tm(t), calculated using the simulator for different functions of the equilibrium temperature TG(H), allows to determine the equilibrium temperature of the rocks. The mathematical model developed provides modeling the temperature distribution during the drilling process. Results of the sensitivity study of the model describe the model sensitivity to the uncertainties in the input data. The calculations of the formation equilibrium temperature from the unsteady temperature data recorded in the well after the drilling completion were performed.