| Gao30oil reservoir is the main block of Huabei Oilfield, which geological reserve is390.43x104t. Until July2012, the cumulative oil production which in Gao30reservoir has been83.55×104t. Currently, the fluid production rate of435.22m3/d, oil production rate of40.34m3/d, the total water cut of90.73%and oil recovery has reached21.38%. However, there still exists a lot of oil in the layer, which has a great potential in tertiary oil recovery for enhanced oil recovery. Due to the high temperature reservoir (113.8℃), high salinity of the stratum water (9601.9mg/L), and serious heterogeneity (Vk=0.768), thus the block has been carried out a number of conventional EOR methods like polymer flooding and weak gel deep flooding. Whereas it can not ideally enhance reservoir sweep efficiency, and is unable to control the degree of mobility ratio because of the low viscosity of the polymer system and the viscosity decreasing to fast, which affects oilfield production.In recent years, the air-foam flooding is a newly efficient developing technology for EOR. The technology includes the advantages of air flooding and foam flooding, and has better oil recovery efficiency. On one hand, it has high apparent viscosity under high temperature and high salinity. On the other hand, it can simultaneously improve the sweep efficiency and displacement efficiency in the mechanism of flooding. Therefore, based on the actual geological conditions of Gao30reservoir, this paper filtrated and got the air-foam system, whose temperature and salinity with strong foaming ability, low and wide effective concentration. And the air-foam adapts to the reservoir, to finish filling sand tube model displacement test. Thus the paper studies on the effects of foam sealing ability and slug size on oil displacement. Finally, this paper bases on the numerical simulation technology to optimize scheme and predict results.Test results show that suitable foaming agent for Gao30reservoir air foam flooding is SD with the concentration of0.1%. The foam system for core has strong sealing capacity, it grows with the increasing of foam concentration, permeability and injection rate, but it decreases with the increasing of oil saturation. The optimal gas-liquid ratio of foam flooding is1.2/1.0. Core flooding effects tests showed that the enhanced oil recovery is increased accompanied with the increase of foam injection system. When slug is0.1PV,0.2PV,0.3PV and0.4PV, EOR increases5.31%OOIP,9.61%OOIP,14.18%OOIP and16.42%OOIP compared with water flooding. Foam system has the ideal choice for sealing, can effectively improve the high and low layer permeability heterogeneity, thus increasing the oil recovery of the low permeability layer’s degree. When injected slug is0.3PV, EOR than water for high and low permeability tube are11.34%OOIP and17.55%OOIP. Optimization of numerical simulation results show that best scheme for injection of Gao30reservoir air foam flooding:main slug0.20PV, in accordance with the gradient type combination slug injection (first main slug0.10PV,0.15%foaming agent concentration; second main slug0.10PV,0.05%foaming agent concentration); pre-slug was0.2%(effective)×0.01PV, gas-liquid ratio is1.2/1.0, injection method is gas-liquid mixture injection. The best predict scheme is that enhanced oil recovery is9.54%OOIP, incremental oil is38.61×104t, incremental oil of tons of foaming agent is200.5t/t. |
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