Research On Combination Operation Technology Of "Profile Controlling And Flooding And Thermal Recovery" In Offshore Heavy Oil Oilfield

With the characteristics of serious reservoir heterogeneity, high permeability and high viscosity of crude oil in Bohai heavy oil reservoir, the oil production was low and the development effect was poor by conventional water injection recovery. Therefore it was urgent to take reinforcing measures to improve the development effect of water flooding. In this paper, theoretically guided by reservoir engineering, physical chemistry and thermodynamics, by means of physical simulation and numerical simulation, taken reservoir geology and fluid of Bohai NB35-2 as experimental condition, research on physical simulation and numerical simulation of polymer gel profile control, multiple thermal fluid stimulation(thermal recovery) and combination operation technology of “profile controlling and flooding and thermal recovery” was carried out, and the field test was conducted in the southern B6 and B20 m well group of the NB35-2 oilfield. Results of physical simulation showed that, compared with the experimental method of electrical heating or injecting high temperature and high pressure thermal fluid into the core, the method of saturating different areas of the core with different viscosity of crude oil to simulate thermal recovery process could not only simulate the distribution of crude oil in the reservoir during the process of thermal recovery objectively, but also took the advantage of better experimental maneuverability and lower cost. In the comparison with single thermal recovery or single profile controlling, the enhancing oil productivity effect of combination operation technology of “profile controlling and flooding and thermal recovery” was better, and the increment of the recovery efficiency was more than the sum of that of the both. The unique synergistic effect showed up. Results of numerical simulation showed that, the main influencing factors of injection well profile controlling and flooding effect were: profile controlling and flooding slug size, concentration of polymer, and flooding displacement time. The main influencing factors of oil well thermal fluid stimulation effect were: thermal fluid cycle injection, thermal fluid soak cycle, thermal fluid temperature, thermal fluid velocity and soaking time. The increment of the recovery efficiency of combination operation technology of “profile controlling and flooding and thermal recovery” was more than the sum of that of single thermal recovery or single profile controlling. On the basis of laboratory study results and the reservoir conditions, B6 and B20 m well group “profile controlling and flooding and thermal recovery” parameters results: thermal fluid cycle injection, thermal fluid soak cycle, fluid temperature, thermal fluid velocity, soaking time, concentration of polymer, polymer slug size, flooding displacement time and production-injection ratio the best levels were: 3500 t, 18 month, 275℃, 150t/d, 3d, 2800mg/L, 0.08 PV, 12 month and 1.4. B20 m well group the best levels were: 3500 t, 18 month, 275℃, 140t/d, 3d, 3000mg/L, 0.06 PV, 12 month and 1.4. In process of “profile controlling and flooding and thermal recovery”, the injection pressure of B6 well increased from the previous 3.23 MPa to 9.25 MPa, and the injection pressure of B20 m well increased from the previous 0.09 MPa to 9.30 MPa. As the injection pressure was raised significantly, the imbibition pressure and imbibition volume of middle and low permeability layers increased greatly. Moreover, the viscosity of reservoir crude oil decreased significantly after thermal fluid injection, and the seepage resistance reduced. So far, the cumulative incremental oil of B6 well group and B20 m well group were 3.10×104m3 and 1.20×104m3 respectively, which acquired the effect of ”increasing oil and decreasing water cut” and provided an effective way for the high-efficiency development of Bohai heavy oil reservoir.