Experimental study of degradable preformed particle gel (DPPG) as temporary plugging agent for carbonate reservoir matrix acidizing to improve oil recovery

Abstract

Preformed particle gel (PPG) is an effective technique for conformance improvement in petroleum reservoirs. It can selectively penetrate high-permeability channels to form effective plugging and divert the chasing injection fluid to low-permeability unswept oil zones. However, conventional PPG would be dehydrated under acidic conditions and could not be easily degraded, which will cause a certain amount of damage to the target formation. Therefore, this study proposed to introduce acid-resistant functional groups and a self-degradable cross-linking structure into the conventional PPG's compositions to develop a degradable PPG (DPPG). The influence mechanism of the chemical composition, swelling performance, and temporary plugging performance of DPPG was studied. Results show that the DPPG can swell up to 70 times its original size by absorbing water, and swollen DPPG can finally self-degrade to a water-like fluid in acid solution. After injecting of DPPG swelled by 20 times its original volume, the injection pressure could reach 1250 psi. Even during the chase acid treatment period, the average pressure was around 130 psi, which shows excellent plugging performance. Subsequent injection of acid would react with carbonate rocks around the plugging zones, increasing the swept volume. In addition, after acid treatments, the DPPG could be self-degraded into a dilute solution like water, so it has very little damage to the reservoir matrix. Therefore, the DPPG has good temporary plugging and acidizing steering performance in acidizing operations. The research in this article can provide the experimental basis and reference for expanding the further application of DPPG in petroleum reservoir stimulation. • Acid-resistant and self-degradable cross-linking structures were introduced to develop a degradable PPG. • The swelling and degradation performance can be adjusted by changing its component concentration. • Coreflooding test reveals that DPPG has a good acid diversion function. • DPPG can undergo self-degradation in a wide range of acidity.