Innovations and applications of the thermal recovery techniques for heavy oil

Heavy oil represents a vital petroleum resource worldwide.As one of the major producers,China is facing great challenges in effective and economic production of heavy oil due to reservoir complexity.Plenty of efforts have been made to promote innovative advances in thermal recovery modes,methods,and processes for heavy oil in the country.The thermal recovery mode has been shifted from simple steam injection to a more comprehensive“thermal+"strategy,such as a novel N2-steam hybrid process and CO_(2)-enhanced thermal recovery techniques.These advanced techniques break through the challenges of heavy oil extraction from less accessible reservoirs with thinner oil layers and greater burial depths.Regarding thermal recovery methods,China has developed the steam-assisted gravity drainage method integrating flooding and drainage(also referred to as the hybrid flooding-drainage SAGD technology)for highly heterogeneous ultra-heavy oil reservoirs and the fire flooding method for nearly depleted heavy oil reservoirs,substantially improving oil recovery.Furthermore,a range of processes have been developed for heavy oil production,including the open hole completion process using sand control screens for horizontal wells,the process of integrated injection-recovery with horizontal pump for horizontal wells,the steam dryness maintenance,measurement,and control process,efficient and environment-friendly circulating fluidized bed(CFB)boilers with high steam dryness,the recycling process of produced water,and the thermal recovery process for offshore heavy oil.Based on the advances in methodology,technology,and philosophy,a series of supporting technologies for heavy oil production have been developed,leading to the breakthrough of existing technical limit of heavy oil recovery and the expansion into new exploitation targets.For the future heavy oil production in China,it is necessary to embrace a green,low-carbon,and energy-efficient development strategy,and to expand heavy oil extraction in reservoirs with larger burial depth,more viscous oil,thinner oil layers,and lower permeability.Moreover,it is highly recommended to collaboratively maximize oil recovery and oil-to-steam ratio through technological innovations,and boost intelligentization of heavy oil production.

Research progress and potential of new enhanced oil recovery methods in oilfield development

This paper reviews the basic research means for oilfield development and also the researches and tests of enhanced oil recovery(EOR)methods for mature oilfields and continental shale oil development,analyzes the problems of EOR methods,and proposes the relevant research prospects.The basic research means for oilfield development include in-situ acquisition of formation rock/fluid samples and non-destructive testing.The EOR methods for conventional and shale oil development are classified as improved water flooding(e.g.nano-water flooding),chemical flooding(e.g.low-concentration middle-phase micro-emulsion flooding),gas flooding(e.g.micro/nano bubble flooding),thermal recovery(e.g.air injection thermal-aided miscible flooding),and multi-cluster uniform fracturing/water-free fracturing,which are discussed in this paper for their mechanisms,approaches,and key technique researches and field tests.These methods have been studied with remarkable progress,and some achieved ideal results in field tests.Nonetheless,some problems still exist,such as inadequate research on mechanisms,imperfect matching technologies,and incomplete industrial chains.It is proposed to further strengthen the basic researches and expand the field tests,thereby driving the formation,promotion and application of new technologies.

Comparison and Optimization of Mid-low Temperature Cogeneration Systems for Flue Gas in Iron and Steel Plants

Three generation systems, namely, steam Rankine cycle （SRC）, organic Rankine cycle （ORC）, and steam-organic combined Rankine cycle （S-ORC）, were simulated using the Engineering Equation Solver fEES） to efficiently utilize flue gas emissions from 200 to 450 ℃ in iron and steel plants. Based on the simulation results for thermal efficiency, exergy efficiency, and power generation, the performances of the three power generation systems were compared and analyzed. To further utilize waste heat from the turbine exhaust steam of the ORC system, cas- cade （）RC （CORC） was designed for heat sources above 300 ℃. Based on a comprehensive performance comparison, the application of the ORC using R141b is preferable for 200 to 300 ℃ flue gas. For 300 to 450 ℃ flue gas, CORC is an alternative technology to improve the efficiency and quality of waste heat utilization. For flue gas above 450 ℃, S-ORC can achieve higher efficiency and power generation than conventional SRC, with a relatively small negative pressure and high dryness of the turbine outlet steam. Hence, S-ORC can be considered as a substitute for SRC.