Lab Study and Field Application of Surfactant Induced Imbibition for Low Permeability Reservoirs

Abstract Low permeability reservoirs are widely distributed in various countries, which contribute an important percentage of oil output in the world. At present the main exploitation mode is water flooding, but the oil recovery is very low. So it is very necessary to develop effective development technology. Chemical flooding technique is one of effective ways to enhanced oil recovery (EOR). However, low permeability may cause injection difficulty of conventional chemical agents (polymers and formulations of chemical combination flooding). Moreover, high temperature or high salinity condition may cause decomposition of the surfactant and polymer with poor long-term stability. For these harsh condition reservoirs, surfactant induced imbibition is an important and promising technology to enhance oil recovery. The key technology is to develop high efficiency surfactant with low cost. In this paper, the novel anionic surfactant has been developed with good capabilities, including good wettability alteration performance, low adsorptions, wide adaptability, good heat resistant and salt tolerant abilities, and high oil displacement efficiencies. Above all, the field test results are good in China. The anionic surfactant could alter wettability from oil-wet to water-wet effectively and had good stripping film capacity. Contact angles were changed remarkably from more than 130° to less than 50°, and oil film could be peeled off in 180 seconds rapidly. The surfactant had good anti-adsorption ability, and it could maintain ultra-low interfacial tension for 5 times adsorption with the natural sand. The dynamic adsorptions of the anionic surfactant on the rock were less than 1.0 mg/g rock, which will meet the requirement of field applications. The anionic surfactant has wide adaptability and good heat resistant and salt tolerant capabilities. The maximum temperature was 160°C, and the maximum salinity was 220,000 mg/L. Core flooding tests demonstrated an average incremental recovery of 12.5% was achieved utilizing imbibition technology. For Qinghai oilfield (low permeability 26×10−3µm2, high temperature 126°C, high salinity 200,000 mg/L) in China, field pilot test of imbibition oil recovery technology was successful. 18 tons of imbibition agents were injected and increased oil production of 3660 tons. Excellent properties of the anionic surfactant indicate that it is a promising surfactant, which can be applied in low permeability reservoirs, especially for high temperature and high salinity reservoirs.