A one-spot pilot was successfully performed in the Sabriaya-Mauddud (SAMA) formation in Kuwait to demonstrate the feasibility of using alkaline-surfactant-polymer (ASP) injection to increase oil recovery from a giant carbonate reservoir. Two Single Well Chemical Tracer (SWCT) tests were performed on the SAMA test well (Well A) to measure the effectiveness of ASP injection in mobilizing waterflood residual oil saturation. The first SWCT test (Test #1) measured the waterflood residual oil saturation (Sorw) after a 10 PV seawater injection. This was followed by the second SWCT test (Test #2) to measure the oil saturation (Sorc) remaining after ASP chemical injection, comprised of: a 0.12 PV alkaline pre-flush; a 0.22 PV injection of ASP; a 0.68 PV injection of polymer in alkali solution; and a 1.00 PV injection of polymer.
The difference in residual oil saturation from Tests #1 and #2 quantitatively determines the overall displacement efficiency of ASP injection. Tests #1 and 2 were performed post water and ASP flooding by injecting dilute SWCT tracer chemicals, including a hydrolyzing, partitioning ester (ethyl acetate) and two alcohols (n-propyl alcohol and isopropyl alcohol) that serve as a cover tracer and material balance tracer, respectively. Residual oil saturation post seawater injection was around 28% (+/- 3%) and following ASP flooding it was reduced to 4% (+/- 3%). These encouraging results confirm the effectiveness of ASP flooding in improving incremental oil recovery relative to waterflooding using seawater.
This paper demonstrates the feasibility of applying ASP flooding to increase oil recovery from carbonate reservoirs. The reported findings will be used to optimize and de-risk the implementation in multiwell/pattern ASP injection.