Analysis of Rock Permeability Variation and Sulfonated Surfactant Concentration in The Oil Recovery By Imbibition and Coreflooding Test in High-Temperature and Waxy Reservoirs

Abstract

Oil production of the mature field in Indonesia is decreasing sharply with one of the efforts to increase oil recovery by implementing Enhanced Oil Recovery (EOR) methods. EOR techniques have been used to minimize the amount of crude oil and petroleum that is left behind in underground reservoirs from conventional extraction methods. One of the proven EOR methods is surfactant flooding. The effectivity of surfactant flooding is influenced by various parameters. Rock permeability and the concentration of surfactant are some of the parameters affecting the oil recovery factor. Rock permeability could affect the effectiveness of surfactant injection performance in the reservoir. The surfactant concentration determination for the slug injection in the reservoir will give an optimum oil recovery by creating a low interfacial tension and microemulsion phase in the high-temperature and waxy reservoir. In this study, an imbibition and core flooding experiment were conducted in the laboratory to determine the optimum surfactant concentration to increase oil recovery with variations in rock permeability for a high temperature and waxy reservoir. In this experiment, sandstone with a permeability range of 5,000-10,000 mD was used with a synthetic brine solution (salinity of 18,000 ppm) that removes scale levels to control the precipitation problem. From the results, the imbibition using only synthetic brine gave only 40% oil recovery, while imbibition using surfactant X#3 solution produced 80% oil recovery. The core flooding experiment at a surfactant concentration of 0.8% with rock permeability of 6,000 mD and 10,000 mD gave the optimum recovery compared with using 0.6% and 1% surfactant concentration. The results gained from coreflooding experiments were 80% RF in 6,000 mD rock samples and 70% RF in 10,000 mD rock samples. In conclusion, surfactant injection using 0.8% concentration into 6,000 mD reservoir layer gave the optimum injection scenario into this reservoir.