This paper discusses the adjustment of water injection in oil formation by adding the expansive granular crosslinked polymer (EGCP) into the injection carrier.

Some pilot tests have been conducted in some reservoirs of Jiangsu, Daqing, Dagang, Shengli and Zhongyuan Oilfield, where water flooding recovery is low due to the channeling in heterogeous oil formation. All pilot tests succeeded in plugging higher permeability water zone to favor the injected water squeezing into lower permeability zones and driving more oil into wells, and the ultimate oil recovery have been obviously increased.

In this paper, laboratory experiments have been done to not only provide experiment data basis for the field application, but also provide the mechanism basis of the EGCP profile modification through porous media. The EGCP system is composed of EGCP and carrier. The carrying fluid should be chosen according to input rate, expansion ratio, transport capacity, EGCP anti-shear ability, and flow resistance. Besides, an optimization analysis based on laboratory data has been made on the types and concentrations of EGCP and carrier, EGCP slug size and EGCP injection time, and profile modification evaluation. Furthermore, micromodel test has been done to study the mechanism of EGCP profile modification. The input rate and expansion ratio of EGCP become smaller, however, the anti-shearing ability becomes strengthener with increasing the salinity of carrie. The water input rate and expansive ratio of EGCP became bigger in polymer carrier, compared with those in formation water carrier, while the anti-shear ability of EGCP became stronger in polymer carrier, the anti-shearing ability further increase with the increasing of concentration of polymer solution. The experiments show that the pressures at the core entrance and middle point can increase synchronously when using polymer solution as carrier. This phenomenon testifies that the ability of EGCP suspension transportation is better in polymer solution, micromodel test further testifies that EGCP has the flow characteristics of "transportation, trapping, re-transportation and re-trapping" when it is flowing through porous media, which is beneficial for diverting the direction of injection liquid to enter the unswept area. The alternation of transportation and trap still can be indicated by pressure changes. The EGCP technique has been further optimized by enlarging EGCP slug size and moving up EGCP injection time to enhance oil recovery. All of these will be beneficial to choose the proper EGCP and carrier, plug large channels, get a good profile modification effect and enhance oil recovery.

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