Известия Томского политехнического университета: Инжиниринг георесурсов (Mar 2023)
MATHEMATICAL MODEL FOR INJECTING VISCOELASTIC COMPOSITIONS INTO THE PRODUCTIVE FORMATION
Abstract
Relevance. Workover of gas condensate wells at abnormally low formation pressures, where Kа<0,2 is a serious problem considering that killing wells with temporary blocking of the bottomhole formation zone is an important stage in well repair. At the same time, the choice of the compositions and parameters of the killing fluid and the technology of their application, which allow controlling hydrodynamic processes in the «well–formation» system, is of particular importance. However, at ultra-low values of the formation pressure anomaly coefficient (Ka<0.2), killing wells and preventing the absorption of killing fluid into the formation become a serious problem due to the lack of appropriate compositions with low densities and methods for controlling hydrodynamic processes in the bottomhole formation zone that meet the requirements requirements. Therefore the compensation of killing fluid insufficient density is possible due to its other rheological parameters, which allow controlling the fluid flow in the «well–formation» system by creating the necessary «barrier» to block the bottomhole formation zone. The use of the method of mathematical modeling for injecting viscoelastic compositions into the productive formation during well killing, with Kа<0,2, makes it possible to control hydrodynamic processes in the bottomhole formation zone and block it. This allows designing the process, evaluating the expected parameters of the technological regime of viscoelastic compositions injection (bottomhole pressure, fluid flow, process duration) into the productive formation and making the necessary adjustments in order to optimize the technological parameters to minimize the negative consequences in well killing. To optimize the process of making managerial decisions during well workover, reduce the time and increase the effectiveness of well killing, it is necessary to effectively plan the technologies used with innovative approaches. Purpose: making a mathematical model for viscoelastic compositions injection during well killing at abnormally low formation pressures (Kа<0,2) and a method for controlling hydrodynamic processes in the bottomhole formation zone to improve the efficiency of gas condensate fields development under conditions of a significant drop in reservoir pressure. Objects: wells of gas and gas condensate fields with abnormally low formation pressures (Kа<0,2). Methods: mathematical modeling. As a theoretical basis, the general non-stationary equations of conservation of mass and momentum of phases in a gas-liquid flow and the equations of oil and gas filtration in the formation are used. A numerical calculation scheme based on the finite difference method is constructed. With its help, multivariate calculations are carried out, the results of which are analyzed. Results. A mathematical model has been made for use for killing wells with abnormally low formation pressures, where Kа<0,2, which allows developing a temporary reservoir blocking project and evaluating the expected parameters of the viscoelastic composition injection (pressure/flow rate, duration). The developed model can serve as the basis for software that can automatically perform the functions of selecting the optimal properties of the blocking composition and its injection modes, based on the criteria for effective killing and subsequent development of wells.
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