(196p) Swelling Behaviors of Cr(III)-Modified Acrylamide-Based Superabsorbent Polymer Microsphere in Brines

Excess water production is one common problem for most mature oilfields worldwide during oil recovery processes, which can lead to rapid productivity decline and significant increases in operating costs. The injection profiles are usually uneven resulting in large amounts of oil left behind the water front. The high permeability strata, or called “thief zones” or streaks which naturally exist in a reservoir or are formed during long-term injection, divert the fluid from uniformly sweeping a reservoir and thus make injected water not effectively sweep the hydrocarbon from adjacent, lower permeability zones, resulting in excess water production and low oil recovery from production wells. A premature shut-in of wells is always obtained because production has become uneconomical. Mechanical isolation and physical plugging of the thief zones have been attempted with degrees of success, but still maintain some serious drawbacks. In recent years, gel treatments are achieved in a subterranean hydrocarbon-bearing formation with high molecule weight water-soluble crosslinked polymer to alter the permeability of the formation during water injection. In-situ gel and preformed superabsorbent polymer (SAP) hydrogel are two common treatment materials with multiple advance properties. However, although several applications are reported, in-situ gel treatment method is proven unsatisfactory because of the inability to achieve desired gelation time and strength in the formation. Preformed particles shows advantages of high rheological strength and transporting ability in porous medium but found with uncontrollable swelling behavior in various salinities in practice which results in difficulties of utilization design. Eliminating the effect of environmental saline solution to swelling behavior is a challenge for synthetic hydrogel system. In our study, Cr(III) is found with promising inhibiting ability after being addressed into the preformed hydrogel. It’s found that on top of the associated crosslinking agent, Cr(III) ions also entail the role of an inhibitor against outer salinity effect after connected with environmental aqueous solution which give rise to modification of the swelling behaviors of the hydrogels. Superabsorbent polymer microsphere gel (SAPG) formed via chromium ion (Cr(III)) (0.521~0.781mM) is synthesized which possess significantly stable swelling behavior. Results show that different with regular SAP hydrogel(no metal ions inserted), SAPG has a property of salinity inhibition of which same equilibrium swelling(ES) ratio are achieved for same sample with various salinity aqueous solutions. In addition, suspension polymerization is conducted to synthesize SAPG through which hydrogel properties are controlled, especially initial size distribution and ES size distribution in varying salinities. The varying salt types and salinities of the fluid carries were used to emulate common salts which could be found in subterranean reservoir in SAP microsphere equilibrium swelling experiment.