石油技術協会誌
Online ISSN : 1881-4131
Print ISSN : 0370-9868
ISSN-L : 0370-9868
初めての海外EOR実証プロジェクト
トルコ国イキステペ油田フィールドテスト
大野 健二
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ジャーナル フリー

1997 年 62 巻 2 号 p. 103-111

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Recently, steamflood and immiscible CO2 field pilots in a heavy oil reservoir in the Ikiztepe field, Turkey were successfully completed by Japan National Oil Corporation and Turkish Petroleum Corporation in collaboration with Japan EOR Research Association. The 1, 400m deep formation is a layered carbonate with 4.3-13.2°API heavy oil with a viscosity of 936mPa. s@Tres=50°C. The primary production by natural depletion was less than 1%. Though the viability of known EOR processes under such adverse reservoir conditions remained uncertain, field pilots were decided to be conducted, since the EOR technologies would give a large impact on recovery of heavy oils in southeastern Turkey.
Both steam and CO2 processes employed inverted 5-spot pattern in areas of 100m×100m and 200m×200m, respectively. High pressure and temperature steam was injected through insulated tubing. After the initial cyclic steam stimulation, continuous injection and production followed. A total of 81, 400 CWEbbl steam was injected and 26, 200bbl of oil was recovered. Low injectivity of the steam and a vertical fracture created during the operation caused lower sweep efficiency. As the thermal conductivity of the insulated tubing was deteriorated with time and injection pressure, significant amount of heat was lost in the wellbore. Due to ultra high temperature, scaling of silica compound caused low operational time of the steam generator.
The CO2 gas obtained from a neighbouring field was subjected to a membrane separation process to raise its purity to over 90%. The continuous injection of CO2 was preceded by three cycles of CO2 huff'n puff. A total of 340 MMSCF gas was injected which resulted in the recovery of 17, 000bbl of incremental oil. Production data indicated that the higher the CO2 gas purity and injection pressure, the higher was the oil recovery due to increased gas solubility into the reservoir oil.
A good simulation history match has been obtained for each process. Additional post-pilot simulation studies included various approach, such as utilizing horizontal wells and injection strategy including a combined steam-CO2 process.

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