The Numerical Transient Simulator (NTS) is a coupled single-well simulator developed by the Applied Geomechanics Research Group (GIGA) of the Petroleum Engineering Program at the National University of Colombia, MedellÍn Campus. The mathematical model is based on single and multiphase flow equation, fully coupled to the stress-deformation equations. The governing equations are discretized in cylindrical coordinates using a second order-finite differences method on a three-dimensional computational grid, composed of an internal domain where flow and rock deformation take place and an external domain, where only deformation can occur. Because in the near-well region stiff pressure, flow and displacements gradients take place, we impose that the nodes separation follows a logarithmic distribution in radial direction. The discretized equations are solved following the IMPES method. The NTS allows the interpretation of a well test by matching pressure and finding permeability modulus and mechanical damage (damage due to drilling and completion operations). In addition, the simulator can evaluate the well production behavior when geomechanical effects exist. The most relevant simulation results provided by the NTS are: pressure distribution, displacement, deformation and stress state, as well as petrophysical and fluid properties distributions throughout the reservoir. In this paper we use the NTS in order to interpret a build up pressure test of a well located in a Colombian field.

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