Why Do Gels Reduce Water Permeability More Than Oil Permeability?
- Jenn-Tai Liang (New Mexico Petroleum Recovery Research Center) | Haiwang Sun (New Mexico Petroleum Recovery Research Center) | R.S. Seright (New Mexico Petroleum Recovery Research Center)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- November 1995
- Document Type
- Journal Paper
- 282 - 286
- 1995. Society of Petroleum Engineers
- 1 in the last 30 days
- 762 since 2007
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A capacity to reduce water permeability much more than oil permeability iscritical to the success of gel treatments in production wells if zones cannotbe isolated during gel placement. Although several researchers have reportedpolymers and gels that provide this disproportionate permeability reduction,the explanation for the phenomenon was unclear. In this paper, we examineseveral possible explanations for why some gels reduce water permeability morethan oil permeability. Our experimental results indicate the disproportionatepermeability reduction is not caused by gravity or lubrication effects. Resultsalso indicate that gel shrinking and swelling are unlikely to be responsiblefor the phenomenon. Although wettability may play a role that affects thedisproportionate permeability reduction, it does not appear to be the rootcause for water permeability being reduced more than oil permeability. Resultsfrom an experiment with an oil-based gel suggest that segregation of oil andwater pathways through a porous medium may play the dominate role in causingthe disproportionate permeability reduction. However, additional work will berequired to verify this concept.
Several researchers reported that polymers or gels can reduce permeabilityto water much more than to oil. This property is critical to the success of geltreatments in production wells if zones cannot be isolated during gelplacement. We have demonstrated that this disproportionate permeabilityreduction is not an experimental artifact caused by hysteresis of relativepermeabilities or by gel breakdown. This property is observed not only withpolymers and "weak" polymer-based gels but also with a monomer-basedgel (resorcinol-formaldehyde) and with "strong" polymer-based gels.
In this paper, we examine several possible explanations for thedisproportionate-permeability reduction, including (1) gravity effects, (2)lubrication effects, (3) gel swelling and shrinking, (4) water and oil pathwayconstrictions, (5) wettability effects, and (6) segregated water and oilpathways. A series of experiments has been performed to assess the relativeimportance of these mechanisms.
Gelants Studied. Four types of gels were used in this study: (1)resorcinol-formaldehyde, (2) Cr(III)-acetateHPAM (Marathon's MARCIT ), (3)glyoxal-CPAM (Pfizer's Floperm 500 ), and (4) 12-hydroxystearic acid-Soltrol130 (an oil-based gel). For the oil-based gel, two formulations wereexamined.Table 1 lists the compositions of these gelants. Pfizer provided thecationic polyacrylamide (CPAM); the 12-hydroxystearic acid used in the lowerconcentration oil-based gel was obtained from Johnson Wax; and Marathonsupplied the partiallyhydrolyzed polyacrylamide (HPAM).
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