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Polyacrylamide polymer flow through carbonate rocks for enhanced oil recovery : an experimental study of polymer-brine stability, resistance factor, and related geologic characteristics
Hunt, James A.
Hunt, James A.
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Abstract
A large portion of the world's crude oil reserves is contained in carbonate reservoirs. The addition of low concentrations of high molecular weight, water-soluble polymers to injection waters has been employed primarily in sandstones to increase oil recovery by improving reservoir areal sweep and displacement efficiency. Based on a comprehensive study of the technical literature, very little experimental work has been performed using polymers in carbonate rocks. A research program was developed to investigate the application of polyacrylamide as a mobility control agent in limestone and dolomite rocks.
The research program was divided into three phases. In the first phase, limestone material obtained from three wells cored in the Lansing and Kansas City Group was examined for adequate porosity and permeability to conduct laboratory core flood experiments. Twenty polyacrylamides were tested for stability in sodium, calcium, and magnesium chloride brine mixtures at 25°C (77°F) and 43.3°C (110°F) for periods up to seven months. Most of the polyacrylamides investigated were found stable in brines containing 27,300 ppm calcium ion and in brines containing 78,700 ppm sodium ion.
In the second phase, ten core flood experiments were performed in reservoir core samples from the Lansing and Kansas City Group, three in Baker dolomite, and one in Berea sandstone. For sections of the core 1 resistance factors and residual resistance factors to polymer and brine were determined from pressure drop measurements. Both resistance factors and residual resistance factors were found to be significantly higher in carbonates than in Berea sandstone.
In the third phase, an attempt was made to relate rock microscopic properties with macroscopic measurements determined from the core flood experiments. Thin sections of the rock material flooded in the laboratory were studied for mineral content, grains, textures, cements, and porosities. The scanning electron microscope (SEM) was used to examine rock and pore cast samples for pore structure. Finally, mercury porosimetery was used to measure the pore size distribution of rock samples flooded in the laboratory. An attempt was made to correlate the resistance factors and residual resistance factors to the geological characteristics studied by thin sectioning, SEM, and mercury porosimetery techniques.
Presented in this paper is a study of the technical literature and each of the above described research phases. Conclusions drawn from the experimental results and recommendations for future research are also presented.
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M.E. University of Kansas, Chemical and Petroleum Engineering 1981
Date
1981-07-31
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University of Kansas
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hunt_1981_737627.pdf
Adobe PDF, 7.84 MB