アブダビ海域におけるサワーガス圧入について

Abstract

Abu Dhabi Oil Co., Ltd. (Japan) operates three offshore oil fields, namely Mubarraz, Umm Al-Anbar (hereafter referred to as AR) and Neewat Al-Ghalan (hereafter referred to as GA) Fields, in Abu Dhabi, United Arab Emirates.AR and GA Fields are oil fields containing high concentration of H2S and CO2 within the associated gas, which are highly corrosive to metal and extremely toxic to humans. The highest levels of precaution for safety were taken in the development policy as well as in the design of the facilities. Meanwhile, gas injection into oil reservoirs had been planned for EOR from the commencement of production, which in turn met the gas conservation policy of Abu Dhabi Government.Given that high-pressure sour gas injection technology was not available in the mid-1980's, H2S and CO2 in produced sour gas had to be extracted by a gas sweetening unit and the sweet gas was then injected into the reservoirs. The sour gas fed from low-pressure separators and acid gas fed from the gas sweetening unit were flared at the artificial island located at the center of the AR Field, namely AR Site Terminal. Since then, various methods to resolve this flaring issue, such as sulfur recovery, production of fertilizer or plaster and disposal of liquid sulfur into underground formations, etc. have been investigated and studied as a priority. However, none of them were economically and/or technically feasible.After a site survey in Calgary, Canada, and in-house extensive studies, it was concluded that sour gas injection was technically and economically feasible. The basic engineering study was commenced in November 1997, and the detail engineering was started in March 1998. The facilities for the sour gas injection were constructed between July 1999 and May 2000 in AR Site Terminal, comprising of two units of low and high-pressure sour gas compressors and one sour gas dehydrator. At the initial stage of the commissioning of the facilities, problems such as vibration of the low-pressure compressors and scale plugging at the strainer were encountered, which caused the delay in the completion of the project.After resolving these difficulties in November 2000, the sour gas injection has been working successfully. The sour gas injection is the first challenge in the Arabian Gulf region, achieving gas conservation, environmental protection and enhanced oil recovery, simultaneously.