Pilot test of CO₂ flooding at Sarukawa oil field

Abstract

JAPEX (Japan Petroleum Exploration Co., Ltd.) executed a pilot test of CO₂ flooding in Sarukawa oil field from 1993 to 2000 collaborating with JNOC (Japan National Oil Corporation). Although CO₂ flooding is a wellknown and well understood EOR technology, it is important to realize how and where injected fluid flows and sweep in subsurface reservoir. Depending on information that suggests the fluid flow in situ, injection and production operation must be adjusted and optimized. A five spot pattern was employed for the pilot test.
In order to realize how and where injected fluid flows and sweep in subsurface reservoir, several measurements, studies, analyses must be conducted. In laboratory, reservoir core analyses, reservoir fluid analyses, PVT of reservoir oil and CO₂ mixtures are typical. Combining those laboratory data with well logging data and well flow test data, numerical simulation models were constructed. Such numerical models were initially utilized for designing pilot test. Before injecting CO₂, water flooding was conducted to obtain history data. After water flooding, CO₂ injection and WAG followed. During and after pilot test, tremendous amount of data, not only history data but also well test data that indicates heterogeneity of target reservoir, were collected and analyzed. Based on those results, original numerical models were modified and tuned to match history data. After history matching, case studies were conducted to understand what was happening in the reservoir, and to predict how the performance should be if operation scheme was varied.
Performance of EOR such as CO₂ flooding is dominated by fluid flow in target reservoir. It cannot be overstressed that the heterogeneity of target reservoir should be well recognized before commercial scale EOR technology is applied.