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.

There are abundant heavy oil resources in Bohai Offshore Oilfield. In past, only limited heavy oil reservoirs are recovered by cold production such as ESP, and uneconomic oil production(less than 30 m 3 /day in general) is obtained. Although conventional steam injection such as cycle steam stimulation is an effective onshore enhancing heavy oil recovery method, it is challenging to setup conventional steam generator on production platform for offshore heavy oil production. In consideration of the pothential of Thermal production for offshore heavy oil recovery, a portable and compact steam and flue gas generator is developed to employ cyclic steam-gas-chemical stimulation, and the whole injection system consists of gas generator, water treatment unit, fuel and chemical tanks, insulated surface pipe and tubing. Steam and flue gas are coinjected at the pressure up to 20MPa, content of flue gas is 13.1wt%-28.3wt%. The stimulation or EOR principles of cyclic steamgas-chemical co-stimulation based on the synergetic effect of fluid injected include reduction in oil viscosity by heating and gas solution, enlargement of heat sweeping efficiency by coinjected gas, decrease in heat loss, expansion of heated porous rock and saturated fluid, improvement in fluid injectivity and sweep efficiency, and reservoir protection or injectivity enhancement and other favorable reaction by chemical additives such as foaming agent. Based on experiment and numerical simulation, the rational temperature of steam and gas coinjected is 300℃, and the volume ratio of gas to steam is about 0.3-1.0 under barometric pressure depending on reservoir condition.In past two years, cyclic steam-gas-chemical co-stimulation are applied to five offshore heavy oil wells completed thermally or non-thermally with screen pipe, periodical steam injection is about 3000-5000 tons, and flue gas generated is injected together, chemical additives such as corrosion retarder injected alternatively, and a certain amount of nitrogen could be injected through annulus between tubing and casing to insulate tubing and vary injected fluid composition. As a result, up to 3 times of oil production rate in average compared to that of cold production is observed, and the peak oil production is more than 100 m 3 /day, and cyclic oil production increase is more than 5000 m 3 . In this paper, EOR principles, injection optimization, engineering design and field testing of cyclic steam-gas-chemical co-stimulation are introduced in detail.

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A brain-computer interface (BCI) translates a user’s thoughts such as motor imagery (MI) into the control of external devices. However, some people, who are defined as BCI illiteracy, cannot control BCI effectively. The main characteristics of BCI illiterate subjects are low classification rates and poor repeatability. To address the problem of MI-BCI illiteracy, we propose a distribution adaptation method based on multi-kernel learning to make the distribution of features between the source domain and target domain become even closer to each other, while the divisibility of categories is maximized. Inspired by the kernel trick, we adopted a multiple-kernel-based extreme learning machine to train the labeled source-domain data to find a new high-dimensional subspace that maximizes data divisibility, and then use multiple-kernel-based maximum mean discrepancy to conduct distribution adaptation to eliminate the difference in feature distribution between domains in the new subspace. In light of the high dimension of features of MI-BCI illiteracy, random forest, which can effectively handle high-dimensional features without additional cross-validation, was employed as a classifier. The proposed method was validated on an open dataset. The experimental results show that that the method we proposed suits MI-BCI illiteracy and can reduce the inter-domain differences, resulting in a reduction in the performance degradation of both cross-subjects and cross-sessions.

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