Experimental Study of Water and CO2 Flooding in the Tight Main Pay Zone and Vuggy Residual Oil Zone of a Carbonate Reservoir

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• 作者：Yanbin Gong ; Yongan Gu
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：October 15, 2015
• 年：2015
• 卷：29
• 期：10
• 页码：6213-6223
• 全文大小：529K
• ISSN：1520-5029

文摘

In this paper, water and CO₂ flooding processes in the upper tight main pay zone (MPZ) and lower vuggy residual oil zone (ROZ) of a carbonate light oil reservoir were experimentally studied and compared. First, some carbonate reservoir rock samples from these two zones in the Steelman oilfield (Canada) were characterized using thin-section analysis and X-ray diffraction. Second, the minimum miscibility pressure (MMP) between the light crude oil and CO₂ at the actual reservoir temperature was determined. Third, a total of eight coreflood tests were conducted with the tight dolomite or vuggy limestone core plugs to examine the effects of the production pressure, CO₂ injection timing, and rock properties on the water- and CO₂-based oil recovery processes in the two different zones. It was found that, for the CO₂ secondary flooding in the non-waterflooded tight core plugs (i.e., the MPZ), the oil recovery factor (RF) was not dramatically reduced when the production pressure was lower than the MMP. For the CO₂ flooding in the waterflooded vuggy core plugs (i.e., the ROZ), however, much less residual oil was recovered in the immiscible case than that in the miscible case, especially after CO₂ breakthrough. In comparison to waterflooding or miscible CO₂ secondary flooding alone, miscible CO₂ tertiary flooding after waterflooding was found to be the most effective method to recover the light crude oil from the tight core plugs and especially from the vuggy core plugs. Moreover, the petrographic properties of these two types of core plugs had rather different effects on the miscible CO₂ secondary flooding, whereas the miscible CO₂ tertiary flooding had similar production trends.