Global warming and reducing fossil fuel resources have increased the interest in using renewable resources, e.g., geothermal energy. In the first step, heat transfer equations have been presented for reservoir during water (steam) injection by considering heat loss to adjacent formations. According to radius of thermal front, the reservoir was partitioned into two regions with different fluid physical properties. The heat transfer model was combined with a fluid flow model which was applied to calculate the reservoir pressure or fluid flow rates. The fluid flow equations in porous media were solved by calculating outer radius of heated region and using radial composite reservoir model. Using pressure derivative plot in regions with different thermal conductivity coefficients, a type curve plot is presented. The reservoir and adjacent formation thermal conductivity coefficients could be calculated by matching the observed pressure data on the thermal composite type curve. Also, the interference test in composite geothermal reservoir is considered. In the composite reservoir model, parameters, e.g., diffusivity coefficient, conductivity ratio and the distance to the radial discontinuity are considered. New type curves are provided to introduce the effect of diffusivity/conductivity contrast ratios on temperature behavior.
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