Laboratory study on high-efficiency viscosity reducer in high temperature and salinity of heavy oil reservoir

Abstract

The Z70 reservoir of Huabei Oilfield is the typical heavy oil reservoir of high viscosity and high contents of gum and asphaltine, while there exists a serious problem that the effect of water injection is poor. In this paper, to increase oil displacement efficiency and improve reservoir development effects, the performance of seven different types of surfactants was studied, which combined with reservoir temperature and oil properties. Then, the emulsifying ability of the system was quantitatively characterized by water diversion rate combined with Turbiscan Lab. At the same time, the performance such as interfacial activity and static adsorption loss was studied under reservoir condition to obtain the viscosity reducing product with high-efficiency emulsification. considering the performance such as interfacial activity and static adsorption loss, the viscosity reducing product with high-efficiency emulsification was preferred for high-temperature and high-salt heavy oil reservoirs. Thus, the surfactant experiment was carried out to test the performance and applicability. one kind of surfactant, nonionic-amphoteric-anionic, was selected, which showed good dispersity and could form super-low interfacial tension with the crude oil of fault block Z70 in Huabei Oilfield. The interfacial tension reached 5×10−4mN/m when the concentration of the surfactants was 0.5%. And the No.1 combined system showed preferable emulsion performance with crude oil which stood for 30 minutes with no water precipitating out. It also provided, after 180 minutes, the emulsion system was completely demulsified, which could be re-emulsified after slight shaking. Good viscosity reducing property was showed with the oil-water ratio range of 1:1∼1:9, which viscosity reduction rate was more than 99.5%. furthermore, low static adsorption loss was showed when the adsorption capacity was less than 4.4mg/g. The experiments indicated that No.1 non-ionic-amphoteric-anionic composite surfactant could be determined to be the efficient viscosity reducer for fault block Z70 in Huabei Oilfield.