Abstract
Preferential fluid flow often occurs when water and CO2 is injected into mature oilfields, significantly reducing their injection efficiency. Particle gels have been evaluated and applied to control the short circulation problems. This study systematically investigated a novel poly(acrylamide-co-vinyl acetate)/alginate-based interpenetrated gel system (Alg-IPNG) which is designed to control the preferential fluid flow problems in high-temperature reservoirs. Chromium acetate was incorporated into the gel system to provide the delayed crosslinking feature of the particle gels. The alginate polymer system can also take advantage of the Ca2+ ions in the formation water, which exist in most reservoirs, to reinforce its strength by capturing the Ca2+ to form Ca–alginate bonds. In this paper, various characterizations for the Alg-IPNGs before and after the self-healing process were introduced: (1) the elastic modulus is set at up to 1890 Pa, and (2) the water uptake ratio is set at up to 20. In addition, we also discuss their possible self-healing and reinforcement mechanisms. In particular, the self-healing starting time of the Alg-IPNG particles are modified between 38 to 60 h, which is related to the water uptake ratio, Ca2+ concentration, and temperature. The reinforced Alg-IPNG gel has an enhanced thermal stability (180 days) at the temperature up to 110 °C.
Highlights
Hydrophilic polymeric gels, known as superabsorbent polymers (SAPs), have attracted broad interest in medicine, drug delivery, drug release, enhanced oil recovery, and so on [1,2]
This study systematically developed and evaluated a chromium acetate-entrapped, self-healing Alg-IPNG preformed particle gel that can be used to plug high-temperature reservoirs that have fractures or fracture-like conduit problems
A stable network structure can be formed by the formation of methylene bisacrylamide (MBAA)-crosslinked poly(AM-co-vinyl acetate (VAc)) and alginate
Summary
Hydrophilic polymeric gels, known as superabsorbent polymers (SAPs), have attracted broad interest in medicine, drug delivery, drug release, enhanced oil recovery, and so on [1,2]. SAPs, which have been often called preformed particle gels (PPG) in petroleum literatures, have been widely investigated and applied to control the preferential fluid flow in reservoirs and reduce water production [3] Compared to their applications in other areas, the SAPs used in sub-surface fluid flow control are required to have controlled swelling ratios, excellent resistance to different ion compositions and reservoir temperatures, and sometimes delayed swelling rates. PPG plugging capabilities have been mentioned in a variety of studies and many approaches have been revealed, such as strength modification [8] and delayed swelling [9] by introducing multifunctional groups to the networks of the gel These improvements cannot meet the blocking requirements of such large fracture-like features.
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