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[S24-2-03] Determination of formation equilibrium temperature and geothermal gradient from temperature measurements in production wells drilled in oil and gas fields
Several ways to determine the parameters of geothermal field according to the temperature measured in the wellbore are known. One of them is the measurement of temperature along the borehole of special wells (control, piezometric). There is a way based on the registration of non-stationary temperature in the borehole after drilling. The idea of the third method consists of the reservoir fluid flowing temperature is recorded as a function of time during the well test. All these methods have known disadvantages and they can be used only in a small number of wells on the interested oilfields.
We have proposed a method of determining the equilibrium temperature of rocks and geothermal gradient from the measured temperature distribution in the producing wells. These measurements are carried out in large numbers on the being developed oil and gas fields. If the well has a sufficiently long sump (for producers it is more than 10 meters), then near the bottom there is zone with undisturbed geotherm.
Rocks equilibrium temperature in this range can be determined with a predetermined accuracy by solving the inverse problem with regard to the speed of device movement and the thermal inertia of sensor. CFD modeling, laboratory experiments and analysis of downhole measurements made it possible to investigate the influence of confounding factors: conductive heat transfer from the working reservoir, a metal casing, free heat convection in the borehole on the distribution of temperature in the sump. Algorithm for correcting the measured temperature along the wellbore is developed. Data on the vertical variation of the thermal properties are used to restore the equilibrium temperature of the rocks outside the borehole sump interval. The paper presents practical examples of using the developed method for the determination of the rocks' equilibrium temperature, geothermal gradients and deep heat flux on the Russian oilfields.
We have proposed a method of determining the equilibrium temperature of rocks and geothermal gradient from the measured temperature distribution in the producing wells. These measurements are carried out in large numbers on the being developed oil and gas fields. If the well has a sufficiently long sump (for producers it is more than 10 meters), then near the bottom there is zone with undisturbed geotherm.
Rocks equilibrium temperature in this range can be determined with a predetermined accuracy by solving the inverse problem with regard to the speed of device movement and the thermal inertia of sensor. CFD modeling, laboratory experiments and analysis of downhole measurements made it possible to investigate the influence of confounding factors: conductive heat transfer from the working reservoir, a metal casing, free heat convection in the borehole on the distribution of temperature in the sump. Algorithm for correcting the measured temperature along the wellbore is developed. Data on the vertical variation of the thermal properties are used to restore the equilibrium temperature of the rocks outside the borehole sump interval. The paper presents practical examples of using the developed method for the determination of the rocks' equilibrium temperature, geothermal gradients and deep heat flux on the Russian oilfields.