Novel Copolymer Thickener for Live Oil CO2-EOR in Secondary and Tertiary Processes

Abstract We investigate the effectiveness of a novel copolymer (copolymer of 1-octene and 1-dodecene with 32 repeating units, C8/C12-32) as a CO2 thickener for enhanced oil recovery (CO2-EOR) at a concentration of 0.3 wt %. The central objective is to evaluate the effectiveness of increased CO2 viscosity and mobility control at low concentration in a live oil. Previous work has focused on a dead oil, demonstrating the C8/C12-32 performance. In this work, we conduct experiments with a live oil. Experiments are conducted using a carbonate core with a 1.5-inch diameter and 10-inch length. CO2 is viscosified by adding 0.3 wt % of the C8/C12-32 at 3500 psi at 120 °C. The viscosity of CO2 is increased by about 2.5 times at 35 °C and 2.1 times at 120 °C. The viscosified CO2 is injected into the live-oil-saturated core in secondary injection, and neat CO2/and brine injection for comparison. In the tertiary process, viscosified CO2 is injected following neat CO2/brine. Under the same conditions, experiments are also conducted using 1.5 wt % C10-20 (an oligomer of 1-decene with 20 repeating units). In the past, we have used the C8/C12-32 oligomer in horizontal dead oil displacement at 3500 psi and 120 °C and 0.3 wt % concentration. In this work, we conduct similar experiments in a live oil. The bubble point pressure is around 2800 psi at 120 °C, and the GOR is about 635 scf/stb. Neat CO2 gives a recovery of about 63 % OOIP. The recovery from the viscosified CO2 injection is about 80 % OOIP. There is about a 27 % additional recovery from viscosified CO2. In the tertiary process, viscosified CO2 is injected following neat CO2 injection (63 % OOIP) and brine injection (57 % OOIP). Injection of viscosified CO2 after neat CO2 increases the recovery to about 72 % OOIP (additional recovery of about 14 %). Injection of viscosified CO2 after brine injection increases the recovery to about 68 % OOIP (additional recovery of about 19 %). Besides 0.3 wt % C8/C12-32 injection, we also conduct experiments using 1.5 wt % oligomer of 1-decne with 20 repeat units. The additional recovery from the viscosified CO2 injection by C10-20 yields about 17 % (secondary) and 18 % (tertiary), which is a substantially lower (secondary, 2-inch), demonstrating the effectiveness of the new thickener. The effectiveness of thickened CO2 is a major step in delaying the breakthrough and adding sustainability by keeping the injected CO2 in the subsurface.