Gel treatment is a technically viable oil recovery method that was deployed to improve conformance and curtail the channeling from fractures, voids, and fracture like features in gas and water flooding. However, facture treatment by using gels can divert gas or water penetration via high permeability fractures and zones and still maintain production zone intact. In-situ cross-linked gels synthesized under reservoir conditions as well as preformed particle gels synthesized at a surface facility before injection have been widely used for controlling conformance in a bid to enhance oil recovery and curtail water production.
In the in-situ gel treatment, the cross linkers and the polymers were injected simultaneously to the target formation where the gel was then formed under the reservoir conditions in order to seal the formation. Unfortunately, some intrinsic drawbacks of gelation quality and gelling kinetic reference to shear degradation, formation of water dilution and chromatographic fractionation, emanated. In addition, the in-situ formed gels had weak metallic bonds and questionable mechanical integrity, which made them vulnerable to break through by gas and water under high pressures.
High permeabilities from fracture-like freak in carbonate fractured oil reservoirs have a huge threat to the oil production while carbonate reservoirs constitute considerably to the United States oil reservoirs. The low oil recovery from the void space conduits carbonate reservoirs in the United States and across the world calls for the synthesis of re-crosslinkable preformed particle gels in an attempt to increase plugging efficiency for chemical enhanced oil recovery.
Conformance control research group led by Lizhu Wang and Baojun Bai in Petroleum Department at Missouri University of Science and Technology demonstrated how re-crosslinking hydrogels could be prepared through a unique method owing to the development of poly-ion complex hydrogels. The weak ionic bonds in-situ distributed within the gels offered toughness, adhesive, and self-healing features to the synthetic cores. The ionic interaction within the hydrogels enabled the authors to prepare re-crosslinkable mechanically robust hydrogels in brine from preformed particle gels. Their research work is published in Chemical Engineering Journal.
The research team prepared the preformed particle gels with re-crosslinkable features to reform bulk gel form chemical enhanced oil recovery of large fractured reservoirs. The researchers were able to realize the development of bulk gel by reversible ionic crosslinks of the preformed particle gels as initiated by brine under reservoir conditions.
The crosslinked gel with ionic attributes indicated mechanically robust attributes. The re-crosslinking capacity of the preformed particle gel under various saline conditions could be controlled by altering the ionic interactions of the monomer pairs. The authors also demonstrated the long-term thermal stability of the re-crosslinked gel. They realized that the re-crosslinked gels could considerably minimize permeability of large fractures as indicated by the core flooding experiments.
The re-crosslinkable gel with robust mechanical features offered a good building block for plugging large fractured reservoirs during water and CO2 flooding for chemical enhanced oil recovery.
Lizhu Wang, Yifu Long, Haifeng Ding, Jiaming Geng, Baojun Bai. Mechanically robust re-crosslinkable polymeric hydrogels for water management of void space conduits containing reservoirs. Chemical Engineering Journal, volume 317 (2017), pages 952–960.
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