Synthesis Of New Surfactants And Their Evaluation For Surfactant-polymer Flooding

Four types of surfactants were synthesized.The synthesized surfactants and the surfactant-polymer mixtures were evaluated under the reservoir condition of the third block of Dagang oilfield Gangxi area.The synthesized surfactants were characterized by FT-IR and MS methods.The suitable surfactant formulations, the concentration with the molecular weight of the polymer were selected by interfacial tension measurement, compatibility, stability of the surfactant-polymer system, anti-adsorbability and flood experiments.Surfactant mixtures were formulated by the synthesized hexadecylbenzene sulfonate and Kelamayi petroleum sulfonate (KPS). The surfactant mixtures could reduce the interfacial tension between Dagang oil and formation water to ultra low values in the presence as well as the absence of polymer. At a concentration.of 0.05 %(0.025% of hexadecylbenzene sulfonate with 0.025% of KPS). The ultra low values could be kept within 28 days for the surfactant-polymer system. The recovery factor was 59.85% of original oil in place when the surfactant/polymer slug size was 0.3 pore volume of the core, compared with 45.59% in case of water flooding.A bolaform surfactant with two sulfonate groups solution could not lower the interfacial tension between Dagang oil and formation water to ultra low values, but it could when mixed with octadecyl hydroxysulfobetaine at a mass ratio of 1:1. When the concentration of the surcatant miture was 0.2%, transient ultra low interfacial tension could be reached even the surfactant-polymer mixtures were aged 28 days and underwent four times adsorption. Core displacement experiment showed that 0.3 pore volume of the mixed surfactant-polymer could improve oil recovery by 11.12% over water flooding; the poor oil recovery might due to the high equilibrium interfacial tension.Experiments showed for the dioctylmethyl hydroxyl sulfobetaine, the equivalent alkane carbon number was about 8, but for the didodecylmethyl hydroxyl sulfobetaine, the number was aroud 10. The surfactant-polymer system could lower the interfacial tension between Dagang oil and formation water to ultra low at the concentration was ranging from 0.2% to 0.3%. The interfacial tension between Liaohe oil and formation water could also be lowered to ultra low when the concentrationof didodecylmethyl hydroxyl sulfobetaine was 0.2%. The surfactant-polymer system could lower the interfacial tension to ultra low, even was aged for more than two weeks when the the the concentrationof dioctylmethyl hydroxyl sulfobetaine was 0.2% and more than 28 days when the concentration was 0.3%. Microscopic flooding experiment showed the residual oil could be started by drawing the oil to oil thread.The oil recovery could be increased by expanding swept volume The sand-pack flooding tests indicated that, with 0.2wt% of the betaine and with 1500mg/L of polymer,16.42% of an additional OOIP (original oil in place) was recovered from a sand pack and 18.53% at the concentration of 0.3%。...