Approval of the combined reserve calculation method (Chervonozayarske Gas Field as an example)

Abstract

The object of the study is the calculation of the producing reserves of the gas-bearing reservoir. Increasingly, published studies provide justification for the possibility of restoring reserves in old depleted gas fields by gas flow from deep horizons. Given the possibility of resuming producing gas reserves, the issue of clarifying their volume in the reservoirs of fields at a late stage of development is promising. In the course of the study, theoretical research methods were used: a system analysis of the inreservoir used, numerical modeling based on a combined finite element-difference method, methods for visualizing the inreservoir obtained, and analytical methods. The method proposed in the paper for refining gas reserves combines the volumetric method and modeling of filtration processes using a combined finite element-difference method. The latter makes it possible to take into account the reservoir structure that is heterogeneous in terms of permeability and adequately describe the distribution of non-stationary reservoir pressure around the production well on a quantitative level. By applying an analytical formula based on the values of average reservoir and bottomhole pressures, the radii of the well feed contour were calculated for different periods of reservoir development. Thus, the active area (and volume) of the reservoir is determined, according to which the calculations of the producing reserves of the field are carried out. The study was carried out on the example of the Chervonozayarske Gas Field (Ukraine) for the reservoir V-26-T-1a, discovered by one production well 468-B(D). The recoverable reserves of the V-26-T-1a reservoir calculated in this way are 597.69 million m3 of gas. At the same time, the error relative to the value indicated in the Atlas of Ukrainian Fields is 4.63 %. The method of calculating reserves proposed in this study is useful for refining the reserves of depleted fields. The combination of the volumetric method with the results of simulation of filtration processes is an operational method for calculating the reserves of a reservoir discovered by one production well. At the same time, the use of a combined finite element-difference method makes it possible to take into account the complex heterogeneous structure of the reservoir and predict the distribution of reservoir non-stationary pressures around the production well.