Abstract

Organically crosslinked polymer (OCP) systems are well-known sealants used for water shutoff in conformance applications. However, in multizone treatments with significant differences in permeability, a diverter is essential to divert the sealant to shut off less-permeable zones. This paper investigates the use of a relative permeability modifier (RPM) as a diverter for the sealant. This solution is most effective at shutting off zones in cases where multiple water-bearing strata with different permeability are encountered. The sealant is proven to be effective, even at 400°F.

Two sandpacks of different permeabilities were formulated. All diversion tests were performed at room temperature and without any backpressure. The RPM adsorbed to the high-permeability zone more than the low-permeability zone. Once adsorbed, the RPM hindered flow of the water-based sealant in the high-permeability zone and diverted it to the low-permeability zone. With higher flow rates, the effect of diversion was lower because more sealant in the low-permeability pack provided resistance for further penetration of the sealant. The RPM and sealant were mixed at different ratios and tested under high-pressure/high-temperature (HP/HT) conditions to observe the effect of mixing on the gelation time for the sealant. The effect of the RPM on gelation time for the sealant was insignificant, provided the polymer and crosslinker concentration of the sealant was constant.

RPMs have been widely applied to decrease the permeability to water in oil and gas wells. RPMs have also been used for acid diversion. The current study shows a new application of using RPMs as a diverter for sealants. This investigation will help increase the potential areas where multizone shutoff using a sealant treatment can be used.

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