Miscible CO2 Simultaneous Water-and-Gas (CO2-SWAG) Injection in the Bakken Formation

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• 作者：Yanbin Gong ; Yongan Gu
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：September 17, 2015
• 年：2015
• 卷：29
• 期：9
• 页码：5655-5665
• 全文大小：541K
• ISSN：1520-5029

文摘

In this paper, miscible CO₂ simultaneous water-and-gas (CO₂-SWAG) injection in the tight Bakken formation is experimentally studied. The effective viscosities of high-salinity water and supercritical CO₂ mixtures with 12 different water volume fractions are measured at the actual reservoir conditions by using a capillary viscometer. A total of six coreflood tests with four different miscible CO₂-EOR schemes are conducted in the tight reservoir core plugs collected from the Bakken formation (Canada). It is found that the measured effective viscosity of the saline water鈥揅O₂ mixture increases with the water volume fraction and can be reasonably modeled by using the Arrhenius equation. The coreflood test results indicate that the miscible CO₂-SWAG injection with an injected water鈥揼as ratio (WGR) of 1:3 in volume has the highest oil recovery factor (RF). The miscible CO₂ water-alternating-gas (CO₂-WAG) injection achieves a slightly higher oil RF than that of the miscible CO₂ flooding, whereas the waterflooding followed by the miscible CO₂ flooding has the lowest oil RF. In addition, the WGR shows strong effects on the fluid production trends of the miscible CO₂-SWAG injection. A water bank might be formed ahead of the water鈥揅O₂ mixture in the miscible CO₂-SWAG injection with a higher injected WGR of 3:1 or 1:1. Furthermore, the mobility ratio of the injected fluid(s) to light crude oil is calculated based on the measured steady-state flow rate and pressure gradient in each coreflood test. In comparison with water or CO₂ alone, the water鈥揅O₂ mixture has a lower mobility in the tight reservoir core plugs. Hence, the highest oil RF of the optimum CO₂-SWAG injection with the lowest injected WGR of 1:3 is attributed to a well-controlled water鈥揅O₂ mobility and a substantially weakened waterblocking effect.