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To improve the oil recovery and economic efficiency in heavy oil reservoirs in late steam flooding, taking J6 Block of Xinjiang Oilfield as the research object, 3D physical modeling experiments of steam flooding, CO 2 -foam assisted steam flooding, and CO 2 assisted steam flooding under different perforation conditions are conducted, and CO 2 -assisted steam flooding is proposed for reservoirs in the late stage of steam flooding. The experimental results show that after adjusting the perforation in late steam flooding, the CO 2 assisted steam flooding formed a lateral expansion of the steam chamber in the middle and lower parts of the injection well and a development mode for the production of overriding gravity oil drainage in the top chamber of the production well; high temperature water, oil, and CO 2 formed stable low-viscosity quasi-single-phase emulsified fluid; and CO 2 acted as a thermal insulation in the steam chamber at the top, reduced the steam partial pressure inside the steam chamber, and effectively improved the heat efficiency of injected steam. Based on the three-dimensional physical experiments and the developed situation of the J6 block in Xinjiang Oilfield, the CO 2 assisted steam flooding for the J6 block was designed. The application showed that the CO 2 assisted steam flooding made the oil vapor ratio increase from 0.12 to 0.16 by 34.0%, the oil recovery increase from 16.1% to 21.5%, and the final oil recovery goes up to 66.5% compared to steam flooding after perforation adjustment. [ABSTRACT FROM AUTHOR]

The development of steam chamber can be used to evaluate steam-assisted gravity drainage (SAGD) performance. The velocity of steam chamber expanding is the key parameter for evaluating the development of steam chamber. Based on SAGD technology theory and heat transfer theory, two calculation model methods, observation well temperature method and steam chamber edge method for estimating the horizontal expanding velocity of steam chamber, were presented. Through analyzing the monitoring data and numerical simulation results of a typical super heavy oil block developed by SAGD in Fengcheng oilfield in Xinjiang, NW China, the development patterns of steam chamber and temperature variation law in the observation well at different stages are determined. The observed temperature data was used to calculate steam chamber expanding velocity. The calculated chamber velocity at different time was applied to predict the temperature distribution of oil drainage zone at the edge of steam chamber and SAGD oil rate. The results indicate that temperature function of high temperature zone in the observation well temperature curve has a linear relationship with measuring depth. The characteristic section can be used to calculate key parameters such as the angle of the drainage interface, expanding edge and velocity of steam chamber. The field production data verify that the results of the two proposed methods of steam chamber growth are reliable and practical, which can provide theoretical support for the efficient development of SAGD. [ABSTRACT FROM AUTHOR]

Steam assisted gravity drainage (SAGD) method for heavy oil exploitation using horizontal wells has been done and successful in the field. In the similar concept with SAGD using horizontal wells, vertical well SAGD has been developed as alternative method. This well consists of two strings where one is as a producer on the bottom and the other one is as an injector on the top. This investigation makes different distance between injector and producer perforations gradually. The aim of this research is to make optimization strategy on the vertical well SAGD. The sensitivities tested consist of injection rate and distance between producer and injector perforations. Analysis result reveals that the impact of multilevel injector will decrease cSOR and improve the production rate on the same injection rate. If the process is combined with multilevel injection rate, the result would offer the most favourable option. Furthermore, the longer distance between producer and injector perforations will cause longer restrained heat in reservoir so that the volume steam chamber will be bigger and drainage radius will be wider. [ABSTRACT FROM AUTHOR]