Preformed Particle Gel for Conformance Control: Transport Mechanism Through Porous Media

Abstract

Preformed particle gel (PPG) has been successfully synthesized and applied to control excess water production in most of the mature, waterflooded oil fields in China. This paper reports on laboratory experiments carried out to investigate PPG transport mechanisms through porous media. Visual observations in etchedglass micromodels demonstrate that PPG propagation through porous media exhibits six patterns of behavior: direct pass, adsorption, deform and pass, snap-off and pass, shrink and pass, and trap. At the macroscopic scale, PPG propagation through porous media can be described by three patterns: pass, broken and pass, and plug. The dominant pattern is determined by the pressure change with time along a tested core (as measured at specific points), the particle-size ratio of injected and produced particles from the core outlet, and the residual resistance factor of each segment along the core. Measurements from micromodel and routine coreflooding experiments show that a swollen PPG particle can pass through a pore throat with a diameter that is smaller than the particle diameter owing to the elasticity and deformability of the swollen PPG particle. The largest diameter ratio of a PPG particle and a pore throat that the PPG particle can pass through depends on the swollen PPG strength. PPG particles can pass through porous media only if the driving pressure gradient is higher than the threshold pressure gradient. The threshold pressure depends on the strength of the swollen PPG and the ratio of the particle diameter and the average pore diameter.

Influence of strong preformed particle gels on low permeable formations in mature reservoirs

“…Reservoirs with high permeability zones and fractures are relatively common in mature reservoirs Liu et al 2010). To solve the problem of reservoir heterogeneity, gel treatments are widely used in oilfields (Zitha and Darwish 1999;Thomas et al 2000;Bai et al 2007a, b;Wang et al 2008;Al-Muntasheri and Zitha 2009;Wu et al 2011).…”

“…These drawbacks include the inability to control gelation time, the uncertainty of gelling due to shear degradation, gelant composition changes caused by chromatographic fractionation effect and dilution by formation water. PPG is created on the surface and injected as gel particles (Chauveteau et al 2001;Pritchett et al 2003;Frampton et al 2004;Rousseau et al 2005;Sydansk et al 2005;Bai et al 2007a, b;Zaitoun et al 2007;Wu et al 2011). PPGs are a better selection than in situ gels from the point of controlling the particle sizes for different reservoir characterization.…”

“…PPGs are a better selection than in situ gels from the point of controlling the particle sizes for different reservoir characterization. Presently, preformed gels contain preformed bulk gels, partially preformed gels, and particle gels (Chauveteau et al 2000(Chauveteau et al , 2001Bai et al 2007aBai et al , b, 2008.…”

“…Particle gels contain PPGs, microgels, swelling micrometersized polymers (Bright Water R ), and a pH-sensitive crosslinked polymer (Coste et al 2000;Chauveteau et al 2000Chauveteau et al , 2001Al-Anaza and Sharma 2002;Pritchett et al 2003;Frampton et al 2004;Huh et al 2005;Rousseau et al 2005;Bai et al 2007aBai et al , b, 2008Zaitoun et al 2007;Roussennac and Tosschi 2010;Zhang et al 2010;Jia et al 2011;Juntail et al 2011a, b). Table 1 displays different types of particle gels used in the oil industry, related studies and the researchers who developed these gels, particle size, and applications.…”

“…PPGs have a collection of compositions which could absorb more than a hundred times their weight in solutions (Bai et al 2007aZhang and Bai 2011;James 2011). In addition, they do not easily release the absorbed fluids under pressure (Bai et al 2007aZhang and Bai 2011;James 2011).…”