Experimental Investigation of Biopolymer Performance in Carbonate Reservoirs under Harsh Conditions

Abstract

Polymer flooding is a mature chemical enhanced oil recovery (CEOR) technology with over forty years of applications at both laboratory- and field-scales. Nevertheless, polymers exhibit poor performance in carbonates due to their complex nature of mixed-to-oil wettability, high temperature, high salinity, and high formation heterogeneity. The main objective of this study is to experimentally evaluate the potential of a biopolymer (Scleroglucan) in carbonates under harsh conditions of temperature and salinity. This experimental investigation includes polymer rheological studies as well as polymer injectivity tests. Rheological studies were performed on the biopolymer samples to measure the polymer viscosity as a function of concentration, shear rate, salinity, and temperature. Injectivity characteristics of this biopolymer were also examined through corefloods using high permeability carbonate outcrops. The injectivity tests included three stages of water pre-flush, polymer injection, and water post-flush. These tests were conducted using high salinity formation water (167,000 ppm) and seawater (43,000 ppm) at both room (25 °C) and high temperature (90 °C) conditions. The rheological tests showed that the biopolymer has a high viscosifying power and exhibits a shear-thinning behavior that is more prevalent at higher polymer concentrations. Also, a pronounced effect was observed for water salinity on both polymer filterability and polymer injectivity. Scleroglucan exhibited better filterability at the high temperature (90 °C) as opposed to the room temperature (25 °C). From the injectivity tests, the shear-thinning behavior of this biopolymer in the porous media was confirmed as the resistance factor decreased with increasing the flow rate applied. Scleroglucan prepared in high salinity formation water (167,000 ppm) showed better injectivity at high temperature compared to room temperature. Meanwhile, Scleroglucan prepared in seawater showed excellent injectivity at both room and high temperatures. Nevertheless, high residual resistance factors were observed for this biopolymer, which might be related to polymer retention and the subsequent reduction in permeability of the porous media. This study provides further insight into the performance of the Scleroglucan biopolymer in carbonate reservoirs and encourages further application under harsh conditions of salinity and temperature.

Date of Award	Mar 2020
Original language	American English