This paper presents a simplified analytic treatment of the problem of fluid flow and heat transfer in a hot water reservoir. A multi-layered reservoir is considered, with a circular array of producing wells surrounded by a concentric, circular array of injection wells. Complete injection of produced water, and hence an eventual steady state, is assumed for the flow system. A temperature gradient is assumed in the radial direction. The rock properties are allowed to vary from layer to layer, but are considered uniform within a particular layer. The heat transfer problem is handled by a modification of the solution to the problem of heat extraction from fractured dry rocks proposed by Gringarten, et al. (1975). The reservoir is represented as a vertical stack of horizontal layers, with permeable and impermeable layers alternating. The pressure distributions in various layers are calculated by spatial superposition of the continuous line source solution for the given geometry, with average fluid and rock properties w i thin the system. This approach can yield results such as the breakthrough time of injected water in each layer, pressure distribution in space and time and the temperature of the produced water over time. In a study of the Heber geothermal reservoir in the Imperial Valley of California such results have shown reasonably close agreement with the result s from computer simulation.

Many hot water geothermal reservoirs display a closed temperature anomaly, i.e., the temperature of the reservoir is highest near the center and gradually declines towards the periphery. For such reservoirs a logical development plan is to produce hot water from the central part of the reservoir through an array or cluster of production wells. The heat is extracted from the produced water for power generation, and the cooled water is injected into the cooler marginal areas of the reservoir through an array of injection wells. This paper presents a semi-analytic method for analyzing the heat and fluid flow characteristics of such a system.

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