Abstract
The first pilot test of surfactant-polymer (SP) flood in the world with mixtures of anionic-cationic surfactants (Sa/c) was carried out for a high temperature low permeability sandstone reservoir with high content of clay to demonstrate the potential of this novel technique to improve oil recovery.
Low critical micelle concentrations (CMC) of 2.78×10−6 mol/L, ultralow interfacial tension (IFT) of 10−3 to 10−4 mN/m when surfactant concentrations were above 0.025 wt%, and lower phase microemulsion with high oil solubilization of 22, as well as 55.45 % oil washing rate were obtained by using Sa/c. The adsorption inhibitor (AI) was adopted to reduce the adsorption because of the high clay contained in the natural core. Dynamic adsorption was about 0.30 mg/g with addition of AI, as well as IFT kept almost unchanged before and after adsorption.
In order to reduce the injection pressure and improve the mobility ratio in the low permeability reservoir, low molecular weight polyacrylamide was adopted. The viscosity of polymer and SP were 2.96 mPa·s and 4.05 mPa·s, respectively. Core flooding results showed more than 16 % original-oil-in-place (OOIP) crude oil was recovered by SP over water flood.
Since August 2012, the pilot test of SP containing Sa/c was carried out in a Sinopec reservoir with temperature of 83 °C, salinity of 15,000 mg/L, permeability of 41.5 mD, clay of 12 %. Totally 0.40 PV chemicals, including 0.1 PV polymer pre-slug, 0.25 PV SP main slug and 0.05 PV polymer drive, were injected from August 2012 to December 2017 with an injection rate of 0.08 PV/a. After that water drive was conducted. Maximal water cut decreased from 82.2 % to 62.1 %, and the peak daily oil production increased from 12.2 t to 32.3 t. The oil recovery was increased by 8.0 % OOIP by the end of December 2018.
