A Novel Re-Crosslinkable Preformed Particle Gel for Conformance Control in Extreme Heterogeneous Reservoirs

Abstract

Preformed particle gels (PPG) have been successfully applied to control conformance for mature oilfields due to its advantages over conventional in-situ gels. However, field applications have demonstrated that current particle gels cannot efficiently plug opening fractures, fractures-like channels, or conduits which exist in many mature oilfields. The objective of this study is to systematically evaluate a new re-crosslinkable preformed particle gel (RPPG) product which can be used to efficiently control the conformance for the abnormal features. The novel particle gels can re-crosslink to form a rubber-like bulky material in the large opening features after placement to significantly enhance the plugging efficiency. We systematically evaluated the effect of temperature, brine concentration and RPPG swelling ratio on the re-crosslinking time, the gel strength after crosslinking, and their thermos-stability. Core flooding tests were run to test whether RPPG can significantly improve the fracture plugging efficiency comparing to a traditional PPG which cannot re-crosslink after pumping. The RPPG can be customized for the mature reservoirs with the temperature from 23 to 80°C with controllable size from tens of nanometer to a few millimeters. The RPPG swelling ratio can be controlled from 5 to 40 times. Its re-crosslinking time can be controlled from 2 to 80 h, depending on absorbed water amount, brine concentration, and temperature. The gel elastic modulus after re-crosslinking can achieve from 300 to 10,800 Pa, depending on swelling ratio. Core flooding tests showed that the breakthrough pressure of the re-crosslinked RPPG can reach up to 300 psi/ft for the fracture with the width of 5 cm and 0.2 cm aperture, which is more than 5 times higher than traditional PPGs. In addition, the plugging efficiency of the RPPG is 20 times higher than 40 K.