Effects of the Heterogeneity of Producing Reservoirs on the form of Pressure Drawdown Curves in Hydrodynamic Investigations of Wells

Methods of mathematical modeling have been used to investigate the problem of pressure distribution in producing reservoirs during conducting hydrodynamic investigations of wells. Using the Laplace transform, an analytical formula has been obtained that generalizes a formula that is known in filtration theory and describes pressure drawdown curves for the case of producing reservoirs represented by interlayers with various filtration characteristics. The obtained formula includes two main terms of an asymptotic expansion at high values of time of the pressure function corresponding to the pressure drawdown curve measured in hydrodynamic investigations of wells.

A method has been suggested for processing data from hydrodynamic investigations of wells in the presence of a straight-line boundary in the reservoirs, separating the permeable part of the producing reservoir and the impermeable rock. This situation may occur in a producing reservoir at a vertical rock displacement due to geological processes in the rock mass. The method is based on the use of logarithmic derivatives of the pressure function against time and allows a quantitative definition of the parameter relating the distance from the boundary to the reservoir piezoconductivity coefficient. A similar method can also be used for analyzing pressure drawndown curves in the case when the presence of an interface is due to the formation of a highly permeable part of the reservoir in the process of local fracturing in the rock. The obtained results can be used for analysis and interpretation of data from field investigation of wells in heterogeneous reservoirs.