Abstract
The polymer flooding process has already been applied to the medium permeability type II reservoirs of the Daqing Oilfield (China) to enhance oil recovery. However, this process faces a number of challenges, such as the flooding efficiency, high injection pressure, formation blockage and damage, unbalanced absorption ratio, and economical justification. In this study, single-phase and two-phase flow experiments are performed to investigate polymer injection adaptability with natural cores of type II reservoirs. The enhanced oil recovery (EOR) effects of the polymer are studied by physical simulation experiments, and the results of application in an actual field are also presented. The results indicate that the flow characteristics and injection capability are dominated by the reservoir permeability in polymer flooding. Moreover, the adsorption of polymer molecules and the injection pressure gradient, which reflect formation damage, are affected more significantly by the concentration than by the molecular weight in type II reservoirs. Using the matching relationship, the injection-production process is stable, and additional oil recoveries of 10%–15% can be obtained in heterogeneous type II reservoirs with a high water saturation. This work is significant in that it further accelerates the application of polymer flooding EOR in medium permeability heterogeneous oilfields with high water saturation.
Highlights
It is well known that crude oil plays an important role in providing energy supply to the world among the various sources of energy
Zitha et al [30] investigated the influence of polymer concentration and permeability on the retention of high molecular weight non-ionic polyacrylamide (PAAm) during flow in granular porous media, and the results showed that the residual flow resistance increased with polymer concentration
The resistance coefficient (RF) and residual resistance coefficient (RRF) of polymer solution injections with different molecular weights and The RF and RRF the of polymer solution injections with3.different and concentrations through natural cores are shown in Table
Summary
It is well known that crude oil plays an important role in providing energy supply to the world among the various sources of energy. In the EOR practice of the Daqing Oilfield, a cost-effective process has been investigated to further produce residual oil from major reservoirs entering the later development period of polymer flooding; for medium permeability type II reservoirs, which have a relatively strong heterogeneity, poor connectivity, thin oil layers, and a small growing sand body, polymer flooding processes for EOR have already been applied and have become a necessity for stable production levels of a maturing field base. The practice of industrialized polymer flooding in the type II reservoir typical blocks of the Daqing Oilfield has proven that an average EOR value of 12.3% (OOIP) can be obtained and has played a significant role in the process of sustainable development of energy [18]. The application of heterogeneous type II reservoirs in the Daqing Oilfield is presented, and the role of a matching relationship between polymer injection parameters and reservoirs in EOR is discussed and explained
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