Experimental evaluation of designed and synthesized Alkaline-Surfactant-polymer (ASP) for chemical flooding in carbonate reservoirs

More than half of the oil and gas resources of the world are hosted in carbonate reservoirs. Also, a total of 60% of their residual oil is left unswept during conventional primary and secondary oil recovery operations. The complexity of carbonate reservoirs due to relative weak water imbibition, undesired capillary forces, low permeability (less than 50mD), oil wetness and geochemical interactions in the presence of formation water high salinity causes precipitation of the injection chemicals resulting in clogging of pore throats and residual oil entrapment. Therefore, taking advantage of purposefully designed chemicals known as alkaline-surfactantpolymer (ASP) for enhanced oil recovery (EOR) applications rather than common commercial ASP materials for these challenging petroleum reservoirs is expected. In this research, the synthesized ASP combination was considered to improve the oil production mechanisms of the desired carbonate porous medium. Ultra-low interfacial tension about 1.6 x 10-3 has been achieved by Alkaline-Surfactant-Nano (ASN) synergistic formulation. Meanwhile, wettability alteration was evaluated by contact angle measurement. The contact angle was reduced from (c) = 155.2 degrees (oil-wet) to (c)= 23.7 degrees (water-wet) by the ASN combination. As well, the remarkable HTHS tolerable and shear resistance synthesized Co-polymer Nanocomposite was applied, and 10 times diluted seawater (losal) was chosen as chemicals compatible aqueous solvent for core flooding experiments. Thus, formulated ASP fluids were synergized by alumina nanoparticles at optimized concentrations of chemicals. Hence, this synthesized ASP is able to improve the residual oil production mechanism and lower the capillary pressure (Pc). 16 chemical flooding scenarios were run on Karanj oil field carbonate outcrop cores; the results of the four successful scenarios with the highest original oil in place (OOIP) recovery percentages are discussed. Experiments results are revealed that the cumulative oil recovery could arrive at 91% under the harsh condition of the reservoir. According to the findings of current research, this ASP formulation is highly recommended for chemical flooding of tight carbonate reservoirs.

Automated summary

More than half of the world's oil and gas resources are found in carbonate reservoirs, but conventional oil recovery processes leave 60% of their residual oil behind. The complexity of carbonate reservoirs, including weak water imbibition, undesired capillary forces, low permeability, and oil wetness, leads to precipitation of injection chemicals and the entrapment of residual oil. Therefore, purposefully designed chemicals known as alkaline-surfactant-polymer (ASP) are expected to enhance oil recovery in these challenging reservoirs. This research focuses on improving the oil production mechanisms in carbonate porous medium using a synthesized ASP combination. The results show promising oil recovery percentages under harsh reservoir conditions.