Fast Calculation of Polymer Injectivity in Offshore Oilfield

Abstract

In the process of large-scale industrial application of polymer flooding in onshore oilfields, an outstanding problem is that uniform injection parameters are not always adaptable to different oil layers, resulting in great difference in production between reservoirs, and sometimes even injection difficulties. The problem is more serious in offshore oilfield, which is guided by early polymer injection and high-rate production. It is important to evaluate the injectivity of polymer solution accurately and rapidly.

Based on the frontal advance theory and equivalent flow resistance method, an analytical mathematical model of polymer injectivity in single-layer reservoir under one-dimensional unstable seepage flow was set up, with the non-Newtonian property of polymer solution and formation of oil bank during the displacing process considered. The injectivity was numerically solved by programming, and was validated with core experiment and numerical simulation. And then multi-layer model was established combined with the characteristics of multi-layer reservoir. Finally, the calculation results were verified by the data of actual polymer injection wells.

The results show that the mathematical model matches well with actual data of polymer injection well, and the calculation precision is within the scope of the engineering requirements. The model can be used to quickly evaluate the injectivity of specific polymer flooding reservoir under actual injection parameters. Moreover, the model has been adopted by field engineers to study the impact of different parameters, such as permeability, oil viscosity, concentration and injection rate. In order to optimize the injection parameters, the calculation results of injectivity are classified according to different formation and fluid properties. Reasonable allocation of the production system is carried out correspondingly. Recent production dynamics of polymer injection well group show that the effect of decreasing water and increasing oil by polymer injection has been further improved.

In summary, a new model for quick and effective evaluation of the polymer injectivity was derived in this work, which is of great significance to guide the design and optimization of polymer flooding in offshore oilfield.

Copyright 2022, IFEDC Organizing Committee

This paper was prepared for presentation at the 2022 International Field Exploration and Devel-opment Conference in **’an, China, 16-18 November 2022.

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