Determination of dynamic drainage area of a gas condensate well, monitoring of aquifer activity, and quantitative evaluation of aquifer performance

This paper proposes a new method for interpreting the results of field studies within three steady-state regimes to estimate the dynamic well drainage area (i.e., pressure disturbance area) for a gas condensate well. The technique takes into account the compaction properties of a reservoir and the thermodynamic properties of a gas condensate fluid system. The described method has been developed based on the Binary filtration model of a multicomponent hydrocarbon fluid system, which considers the gas condensate mixture as a composition of two pseudo-components. This model takes into account the phase transformation of pseudo-components and the mass exchange between the phases. The implementation of the new method requires data on well flow rates measured within three different steady-state conditions. The presented algorithm is verified using several examples covering wide range of formation pressure changes and rock compaction factors. Applying this methodology, for example, with PVT data of gas condensate mixture of the VIIth horizon of the Bulla-Deniz field (Azerbaijan) at various reservoir and bottomhole pressures, it was revealed that the mismatch between calculated values of the well drainage area and the actual values varied within a range of 0.97 to 2.6% and 0.58 to 1.9% error for non-deformable and deformable formations, respectively. With the introduction of the concept of an “imaginary well” (enlarged well), an expression was obtained for monitoring the activity of an aquifer. And for the first time, an approach for the numerical assessment of aquifer activity based on Jamalbeyli indexes has been proposed.