Although there is abundant heavy oil resource in Bohai oilfield, only limited oil production is obtained by non-thermal production technologies such as ESP in past. The practical challenging of thermal production technologies, for instance, CCS and SAGD is the difficulty to install the large conventional steam generator onto offshore production platform.
In order to recover offshore heavy oil in Bohai Oilfield, the largest offshore oilfield in China, at large oil production rate in the limited production platform lifetime, a portable steam and gas generator is developed to produce high temperature and high pressure steam, CO2 and N2 on production platform using diesel oil or natural gas as fuel. The temperature of produced steam could be regulated, usually 150 to 300, and the pressure is up to 20MPa. The components such as fuel tank, water treatment, air injection unit could be easily resembled on the production platform. The steam generated and exhausted CO2and N2 could be injected into oil well to stimulate offshore heavy oil reservoir in huff and puff or SAGP processes.
In past three years, there are 2 non-thermally completed heavy oil wells and 7 thermally completed heavy oil wells are successfully stimulated by co-stimulation with steam and flue gas generated by above generator. As a result, the gas generator is operated soundly, the engineering design and related implement techniques such as insulation, sand control and corrosion inhibition are feasible, and oil production rate increased obviously (more than 100 m3/day oil production rate obtained, it is up to 5 times than cold production), total increased heavy oil production compared to cold production per cycle is about 5000m3 to 10000m3. Primarily, it shows that co-stimulation is much effective and practical for offshore heavy oil production.
In this paper, cases of co-stimulation with steam and flue gas are introduced in detail, and related techniques and practices discussed as well.