Coupling Low Salinity Water Flooding and CO2 Flooding for Sandstone Reservoirs; Low Salinity-Alternating- Co2 Flooding (LSAGF)

Abstract

Low salinity water flooding and Co2 flooding are two novel combination floods was coupled due to the important role of both of methods in increasing oil recovery. Low salinity was examined by many laboratory and field works and it showed an interesting result in increasing oil recovery. Co2 was tested on increasing oil recovery and the oil recovery increased by improved wettability alteration effect towards more water-wet, and interfacial tension reduction. Although the Co2 showed an improvement in oil recovery, the density difference between Co2 and oil raised a gravity override, channeling, and early breakthrough problems. For that reason, we develop the low salinity alternating Co2 flood to gather the benefits of low salinity itself and to improve sweep efficiency by Co2 and prevented Co2 problems mentioned earlier as well as capturing the Co2 from the atmosphere. This method can be considered as a low-cost method since it needs only water and Co2. Numerous Berean sandstone cores with analogous petrophysical properties were saturated with a synthetic formation water, the water was displaced with crude oil to Swi, and then allowed to age for three weeks at 90°C. These cores were then flooded with two pore volume (PV) high salinity (HS) and then followed by one PV low salinity (LS) water at room temperatures. The HS water was identical to the formation water, while the LS water was diluted 100x (symbolized d100HS) from the HS water. HS water was injected into the cores until (Sor) was reached. The new combined technology was conducted by five scenarios on five cores: (1) One PV Co2 followed by two PV LS water. (2) 0.5 PV Co2 + 1 PV LS water + 0.5 PV Co2 + 1 PV LS water. (3) 0.25 PV Co2 + 0.5 LS water + 0.25 Co2+ 0.5 LS water (4) Huffed 0.9 PV Co2 and puffed it after two hours, then 0.5 LS water was injected+ 0.5 Co2 +0.5 LS water. The laboratory experiments of all scenarios showed an incremental oil recovery, but the optimum scenario was the scenario (5) with incremental oil recovery 14.5% of OOIP. The two hours huffing make it easy for the following flooding LSASF. While scenario (3) was the second optimum with incremental oil recovery 11% of OOIP because the short cycle injected of LS water and Co2. In this paper, simulation work was conducted to visualize the new coupling method. This combination technology can solve the Co2 flooding problems and support the Co2 by LS water which is itself could increase oil recovery by altering the wettability towards more water-wet.

AAPG Datapages/Search and Discovery Article #90335 © 2018 AAPG 47th Annual AAPG-SPE Eastern Section Joint Meeting, Pittsburgh, Pennsylvania, October 7-11, 2018