The influence of contamination of the bottom-hole formation zone and the of perforation channels parameters on the productivity of gas wells

Abstract

The reasons and nature of contamination of the bottomhole zone of wells are characterized. The structure of the skin effect is revealed. The characteristics of the types of well completion and the main parameters that are necessary to determine the skin effect are given. For the conditions of a hypothetical well, using the PipeSim program from Schlumberger, the influence of the permeability and thickness of the contaminated bottomhole formation zone on the value of the skin effect is investigated. The graphical dependences of the skin effect of the contaminated zone on its thickness and permeability are shown. The results of graphical dependencies are processed using statistical analysis. According to the research results, the value of the skin effect increases with the decrease in the permeability of the contaminated zone relative to the permeability of the productive formation and with the increase in the radius of the contaminated zone. The improvement in the filtration properties of the bottomhole formation zone occurs with the increase in the permeability of the contaminated zone compared to the formation permeability. The optimal values ​​of the permeability and thickness of the contaminated zone are obtained, above which the skin effect practically does not change. The study of the influence of the quantity and size (length and diameter) of perforation channels per one meter of the open layer thickness is carried out. The research results are shown on the graphical dependences of gas flow rate and bottomhole pressure on the number of perforations per one meter of the open formation thickness, their length and diameter. The use of perforation channels that pass through the conta-minated zone has been substantiated to improve the hydrodynamic connection of the formation with the well and increase the gas production rate. According to the results of studies carried out using the McLeod model, the optimal diameter of the perforation channels is 0,029 m, the length of the channels is 0,296 m, and the number of channels per meter of the open formation thickness is 16.