The Mechanism Study Of Hydrocarbon Gas Injection And The Optimization Of Gas Huff And Puff In JAKE-S Reservoir

Enhance oil recovery technology (EOR) is one of the permanent topics in research on oil/gas reservoir development. In recent years, the demand for chemical drive is keeping decreasing and for gas drives increasing. The reservoirs of most of oil fields in China are non-marine deposits with serious heterogeneity and high viscosity crude. Therefore, the water flooding recovery is still low even if the enhanced injection-production system has been taken, only about33%, and2/3of the geological reserves still stay in the ground.Therefore, the development of enhancing oil recovery technology has become an urgent strategic task for sustainable development of the oil industry.As one of the important methods of enhancing oil recovery, people pay more and more attention on gas flood recovery. Methods in gas injection EOR methods increased in recent years a larger proportion. The basic principle to enhance oil recovery of gas injection is:injected gas is vaporized and extracted from the crude oil, or the hydrocarbon in the injected gas condensate to the formation oil, until there is a large enough alkenes zone at the flooding leading edge, and reach non-miscible or miscible state. In Immiscible displacement, vaporization and extraction reach dynamic equilibrium; in miscible flooding, vaporization、extraction and the role of the condensate stop, while at the leading edge of miscible phase, due to diffusion, dispersion and mixing, viscous fingering and slug dilution, the miscible zone may be destroyed gradually until mixed phase disappeared. Then, the above effects happen again to re-establish mixed phase. In the entire displacement process, the miscible phase zone forms, disappears, re-forms until flooding, only a small amount of residual oil is leaved.EOR by injecting gas method has two ways; one is miscible phase, while another is immiscible phase. On the of gas drive’s classification there are many, according to different types of injected gas, there are many computational methods on gas drive,it can be divided into hydrocarbon flooding and non-hydrocarbon flooding. Among them, hydrocarbon flooding covers dry gas (lean gas) drive, rich gas drive, liquefied petroleum gas (LPG) slug and so on,and the non-hydrocarbon flooding covers carbon dioxide flooding, nitrogen flooding, flue gas drive and so on. However, according to the different miscible phase mechanism, the gas injection miscible displacement can be divided into two kinds, the one is the first contact miscible flooding such as LPG slug, and another is multiple contact miscible displacement. Multiple contact miscible displacement can be further divided into two kinds, the first is condensate gas drive, such as gas-rich drive, the second is the vapor drive, such as carbon dioxide drive, dry gas drive, nitrogen drive, flue gas drive. Hydrocarbon displacement is a method of enhancing oil recovery, which injects lighter hydrocarbons into the reservoir to build miscible displacement. It includes high-pressure dry gas drive (vapor drive), rich gas drive (condensate gas drive), and LPG segment plug drive (first contact miscible phase).Injecting hydrocarbon gas is proposed as a measure to maintain reservoir pressure. The hydrocarbon gas can be methane (dry gas), the rich gas, and liquefied petroleum gas like propane. In the relatively low pressure, according to the composition and temperature of the oil in place, these gases are can be mixed with crude oil, or in the process of drive developing into a mixed phase. Even if it can not reach the mixed phase between the injected gas and crude oil, through gas-liquid mass transfer, gas dissolved will also make the oil volume swelled and viscosity decreased. The supplement of formation energy and gravity stable displacement mechanism can also play a role in enhancing oil recovery. Therefore, Hydrocarbon gas injection can maintain reservoir pressure, It will has not any effect to reservoir rocks, could not contaminate reservoir. And the injected gas can be recycled, so it can be used as a storage method, to prepare for future needs. In addition, the injected gas can effectively eliminate the interfacial tension and capillary pressure, minimize the residual oil saturation. In short, the main mechanism of oil displacement of the volume expansion, viscosity reduction and gravity stable displacement, the main advantage is not to harm the strata, and hydrocarbon gas drive is applicable to the development of rich gas condensate reservoir.The dissertation is supported by the overseas projects of China National Petroleum Turpan-Hami Oilfield-the study of gas injection of Sudan JAKE-S oil field. Jake-S reservoir has good properties, low viscosity of crude oil and rich gas source, and has basic conditions for gas drive, water-alternating-gas drive and high-speed exploration. The reservoir has a good capability of gas absorption and water absorption--enough to meet the needs of various options to injection and gas injection. Therefore, according to characteristics of JAKE-S, it has very important meanings to doing this research of gas drive.The purpose of this paper is based on the theory of enhancing oil recovery by gas injection, through numerical reservoir simulation technology to establish mechanism model and expand the mechanism study of injecting hydrocarbon gas to enhance oil recovery in JAKE-S reservoir. At the same time, whereas the oilfield has used the way of gas throughput to mining and the results were quite good in early stage, this article will optimize the gas throughput parameters further of JAKE-S reservoir, research the main factor affecting the development effect (considering the cycle of gas injection, injection rate, fluid production speed, soak time, etc.), determine the optimal throughput program. The article is composed by four main chapters as follows:(1) Characteristics evaluation research of JAKE-S reservoir.On the basis of the reservoir information of the Sudan JAKE-S oilfield, paper mainly includes seven parts:Reservoir geological characteristics, evaluation of reservoir properties, reserves calculation and evaluation, reservoir natural energy evaluation, reservoir capacity, economic well density and oil reservoir pressure system.(2) Mechanism analysis of hydrocarbon gas driving.Explore and the summarize the mechanism of hydrocarbon gas driving, and we can understand the status quo of the gas injecting at home and abroad to improve oil recovery through literature research, and select and analysis the typical case of gas driving to enhance oil recovery.(3) The mechanism research of hydrocarbon gas injection to enhance oil recovery of JAKE-S reservoir.Through the establishment of the mechanism model, use numerical simulation, and use the CMG reservoir simulation software, the following six aspects are carried out:①the way of injection.②pen position and open extent of injection and production wells.③continuous gas driving parameter optimization.④gas injecting parameter optimization of the water-alternating-gas flooding to enhance oil recovery.⑤sensitivity analysis of gas throughput.(4) The optimization program design of JAKE-S reservoir natural gas throughput.Design natural gas throughput program of the JAKE-S reservoir, and study the main factor affecting the development effect (considering the cycle injection volume, injection rate, soak time, etc.), and determine the optimal throughput programs.