Method of Interpretation Interference Tests of Horizontal Wells in Anisotropic Reservoir

Interference between wells provide an important information about reservoir characteristics such as permeability, lateral anisotropy (azimuth and ratio), vertical anisotropy. There are some well-known analytical methods for interpretation of interference tests, however they are valid for vertical wells and can be applied to interpretation of horizontal wells test only under the assumption of large distance between wells. Analysis of horizontal well interference tests is a difficult problem which is based on mathematical model of the reservoir. The mathematical model demands solution of the diffusivity equation which describes the single-phase fluid flow in porous media. This equation can be solved numerically, but it can be time-consuming process that restricts the application of this techniques for inverse problems of interference test analysis. In [1] it was proposed method for solution the diffusivity equation used Green’s function technique together with Ewald’s summation algorithm. The last one is a special case of the Poisson summation formula and it allows to solve the diffusivity equation efficiently. It was obtained analytical expression for time-dependent pressure behavior in a reservoir penetrated by horizontal well. The purpose of this work is to provide tools to evaluate reservoir parameters from horizontal observation well pressure response influencing pressure transient created by horizontal and vertical wells in reservoirs. Within the method presented in [1], the analytical expression for observation well pressure time response is obtained. This expression is obtained at the suggestion of the bottom hole pressure is a constant along well trajectory, but it can be time dependent variable. Any assumptions about sufficiently large distance between wells were not used. We consider inference tests between several horizontal wells and a vertical well in anisotropic reservoir which was realized as a research work in a Western Siberian greenfield. Estimation of reservoir characteristics is achieved by solving inverse problem, where the mathematical model of reservoir generates the pressure response to the actual one closely. A detailed sedimentology study was used to choose the initial value of lateral anisotropy azimuth. It is shown this value is in a good agreement with the same one defined from hydrodynamic computation. The series of multidirectional interference tests allow to verify the obtained analytical results. The results of analytical interpretation were validated by matching with numerical results, performed in 3D simulators. [1] E.S.Makarova, S.V. Milutin, D.V.Posvyanskii, V.S.Posvyanskii ECMOR XII P007 2010