Research On The Aerating Surfactant Flooding For Heavy Oil Reservoir

Gas-surfactant flooding technology was proposed for conventional heavy oil reservoirs. The surfactants must have good emulsifying power and foaming ability, hence the molecular sructure of a nonionic-anionic Gemini surfactant was designed. A series of sulfate nonionic-anionic Gemini surfactants were synthesized after optimizing the synthetic conditions of their intermediate—Gemini diol. Then the foaming ability and the capacity to reduce IFT of these Gemini surfactants were evaluated. The results show that the Gemini surfactant of 9BS-5-0 which contains five oxypropylene groups has equivalent foaming ability with the common surfactant AOS; 9BS-5-0 with the mass fraction of 0.3% can lower IFT to 0.01mN/m, exibiting better performance than Shengli petroleum sulfonate and heavy alkylbenzene sulfonate ( more than 0.05mN/m ); Furthermore, its emulsifying capacity is much higher than these common surfactants too. Alkali and alkali-free compound systems can be obtained by combining 9BS-5-0 respectively with alkaline and betaine. The two systems have goog ability to reduce interfacial tension and emulisify crude oil ( minimum rotation rate is lower than 250r/min ), and good foaming ability ( foaming volume is larger than 500ml). So they can be used in N2-surfactant and CO2-surfactant flooding.Gas-surfactant core plugging tests were carried out with the displacing systems developed from 9BS-5-0. The results indicated that the foams generated under the same gas/liquid ratio have better plugging effect on the oil-wet cores with permeability of 2.409μm2 and 3.340μm2, but worse plugging effecton the one with permeability of 0.286μm2. While for the water-wet cores, the lower permeability, the better plugging effect. The comparison and analysis of the plugging ability difference between foam and HPAM indicate that foams with GLR 0.1, 0.125 obtain the same resistance coefficient as HPAM solution with viscocity of 40mPa·s in oil-wet cores whose permeabilities are 2.409μm2 and 3.340μm2, and for the water wet core with permeability of 1.627μm2, the resistance coeifficent generated by foam with gas and liqulid ratio of 0.156 is as large as that generated by HPAM solutuin with viscocity of 20mPa·s. So it can be improved that low gas/liquid ratio foam has good plugging effect on the core with a certain permeability and provides support for the foam flooding with low gas and liqulid ratio. Gas-surfactant core flooding tests for Zhuangxi heavy oil (327mPa·s at 50℃) suggest that gas-surfactant systems with gas-liquid ratio ranging from 0.15 to 2.0 can achieve relatively high oil recovery. Micromodel flood tests show that the gas-surfactants can improve displacement efficency by emulsifying and sweep efficiency by Jamin effect, and drive residual oil in blind ends and on pore walls by compression and entrainment of foam.Based on lab tests, gas-surfactant flooding pilot tests were carried out in three well groups of Zhuang106 block. The cumulative net oil increment amounted to 14128t regardless of production decline, and composite water cut was reduced by a maxium of 5.11% by the end of September, 2009.