Analysis and planning multi-well system performance in a heterogeneous reservoir is one of the main tasks of field development. In the paper it is shown that performance of multiwell system can be described using Multi-Well Productivity Index (MPI) concept. MPI is an extension of the Productivity Index (PI) to a multi-well case. It reflects the relation of pressure drawdown and rates of wells of a multi-well system. The diagonal coefficients of MPI correspond to the classical productivity indices of each well, and the off-diagonal elements reflect the inter-well connectivity. It is possible to calculate the MPI matrix coefficients analyticaly only in case of homogeneous reservoirs of simple form. This is why MPI approach was not widely used in practice.
The paper shows the engineering method for estimating the MPI matrix coefficients using the data of monthly technological regimes and a priori geological information for the general case of heterogeneous reservoirs. This approach is based on the solution of the filtration equations with Boundary-Element Method (BEM) and the subsequent reduction of these equations to the form of MPI matrix. It is possible to reduce BEM equations for calculation of the MPI coefficients explicitly for the case of reservoirs with no internal faults and wedging zones. For reservoirs with faults and wedging zones the numerical algorithm for estimating the MPI indices is proposed. Estimation of MPI indices for heterogeneous reservoir allows to solve various field development problems: waterflood optimization, workover and welltest planning etc.
An important advantage of the proposed algorithm over other engineering tools for determining the inter-well connectivity, including the so-called CRM-models (capacitance resistivity models), is that the proposed approach allows to take into account explicitly a priori geological information, such as the presence of impermeable faults, the shape of the reservoir boundary, the aquifer, well completion etc.
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