The effects of shear history on the gelation of polyacrylamide/chromium(VI)/thiourea solutions
The influence of shearing during gelation on the gelation rate of a polyacrylamide/chromium(VI)thiourea solution was studied. Gelations were carried out under steady-state shear, oscillatory shear, and programmed shear. When shear rate was constant throughout the experiment, gels formed more slowly at high than at low shear rates. This behavior is opposite to that observed with polyacrylamide/chromium(VI)bisulfite solutions, where increased shear rates led to faster gelations. The gelation mechanism is believed to involve at least two chemical reaction steps: reduction of chromium(VI) to chromium(III) followed by crosslinking of the polymer by chromium(III). In gelation with bisulfite as the reducing agent, chromium(III) is generated rapidly, and the rate-determining step (which may be polymer-diffusion controlled) is probably the crosslinking of polymer by chromium(III). In contrast, chromium(III) is generated relatively slowly in gelation with thiourea as the reducing agent, and the rate-determining step appears to be the redox reaction. The conclusion that the rate of gelation and strength of the gel formed for the gelation of polyacrylamide by chromium(III) are strongly influenced by the total shear history of the solution has important implications for design of field applications of gelled polymers in EOR. The evaluation of gel characteristics is quiescent bottle tests, a common practice, may not be sufficient to determine whether a gel of the desired strength can be obtained in situ because all gelling solutions must be subjected to considerable shearing during injection.
- OSTI ID:
- 6632973
- Journal Information:
- SPE (Society of Petroleum Engineers) Reserv. Eng.; (United States), Journal Name: SPE (Society of Petroleum Engineers) Reserv. Eng.; (United States) Vol. 3:4; ISSN SREEE
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ANTITHYROID DRUGS
CARBONIC ACID DERIVATIVES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM
CROSS-LINKING
DATA
DISPLACEMENT FLUIDS
DRUGS
ELEMENTS
ENHANCED RECOVERY
EXPERIMENTAL DATA
FLUIDS
GELATION
HORMONE ANTAGONISTS
INFORMATION
INJECTION WELLS
KINETICS
METALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC POLYMERS
ORGANIC SULFUR COMPOUNDS
POLYAMIDES
POLYMERIZATION
POLYMERS
REACTION KINETICS
RECOVERY
REDOX REACTIONS
SHEAR
THIOUREA
THIOUREAS
TRANSITION ELEMENTS
WELLS