Natural polymer flow behaviour in porous media for enhanced oil recovery applications: a review

Abstract

When a reservoir is flooded with polymer, the mobility ratio between the displaced fluid and the displacing fluid become favourable compared to the conventional water flooding. In the oil and gas industry, the synthetic polymer polyacrylamide in hydrolysed form and the biopolymer xanthan are being used for this purpose. However, the polyacrylamide is susceptible to high temperature and salinity. Also, its synthetic nature makes it harmful to the environment. The biopolymer xanthan has the problem of degradation and both are very expensive. With the shortfall in crude oil price and the high cost of exploitation and drilling new wells, there is need to look inward and think out of the box in formulating new improved polymers that can combat these problems. Natural polymers from agricultural and forest produce are abundant in nature, cheap and environmentally friendly. These agricultural and forest produce contain starch and cellulose which are known to have rigid and long polysaccharide chains that can withstand the harsh reservoir conditions. But the design of a polymer flood or a permeability-modified process involving polymer requires knowledge about the polymer flow mechanism and the rheological behaviour of the porous media. This paper, therefore, reviews the available natural polymers that can be used for enhanced oil recovery applications and the mechanism affecting their flow behaviour in porous media. The emphasis is on the physical aspect of the flow, the microscopic rheological behaviour of the natural polymers. The dominant mechanism of the flow process was adsorption, mechanical entrapment and hydrodynamic retention. It was observed that the polymer exhibited non-Newtonian, pseudoplastic and shear-thinning behaviours. The literature review on oil displacement test indicates that natural polymers can recover additional oil from an oil field. Environmental application issues associated with the application of natural polymers have opened new frontier for research and are also highlighted herein.