In one aspect, a new class of particle gels that can re-crosslink at subterranean conditions, wherein maintaining stable in supercritical CO2, is described in this invention. The inventive particle gel disclosed is called CO2 resistant re-crosslinked preformed particle gel (CO2-RPPG). This CO2-RPPG comprises polymer matrix, crosslinker I, crosslinker II, and additives, wherein all aforementioned compositions are homogeneously distributed in the CO2-RPPG when synthesized. The polymer matrix comprises three moieties that are re-crosslinking moiety, acid resistance moiety, and CO2 philic moiety. They are respectively functioning in re-crosslinking with crosslinker II, preventing particle gel from dehydration and tuning the affinity of hydrophilicity and CO2-phicility.
The disclosed and claimed invention herein, in another aspect, comprises a CO2 plugging method that is in regard to the deployment of re-crosslinkable particle gels. In the oilfields, the particles can be pumped using brine or produced water as the carrier fluid. In subterranean conditions, the particles preformed by polymer matrix and croslinker I will transport along with the unreacted crosslinker II that is absorbed on the matrix, wherein all constituents move as an entirety. After the placement into target zone, the particles accumulate in the fractures or conduits, wherein crosslinker II will gradually desorb from the precursor. Under the stimulus of reservoir temperature, the active crosslinker II will render all particles stick together, and thereby generate an elastic bulk gel based on the crosslinking reaction. This process, particularly the processing time, will be dependence on the reservoir temperature and the salinity of carrier fluid, whereas can be artificially controlled by introducing reagents or additives. After re-crosslinking, the stable gel with good mechanical integrity will block the target zone or bypassing zone, and thereby divert the chased fluid (e.g., CO2 or water) to the unswept zone; the re-crosslinked gel as a robust CO2 plugging agents will not undergo dehydration or other chemical degradations induced by CO2. The inventive CO2-RPPGs herein overcoming the inherent inferiors of pristine particles and aqueous polymer gels such as extrusion, dehydration, mechanical vulnerability and thereof, will become a superior alternative for CO2 conformance control and CO2 leakage blocking.
Owner: University of Missouri Science & Technology
IP Protection Status: Unknown