This paper presents the Mobil Oil Indonesia experience associated with cementing the 9-5/8 inch casing through the abnormally pressured and water sensitive sand/shale Baong formation in the Arun field. North Sumatra.

The paper will discuss how the cement slurries and cementing procedures for the 9-5/8 inch casing have been modified to overcome two major problems. The first being the inability to fully displace the cement due to swelling of sensitive shales, the second being severe annular flow after cementing.

This paper will further examine the changes made to slurry design after the recent discovery that circulating temperatures during 9-5/8 inch cementing operations are considerably lower than predicted by the API schedules. Because of these low temperatures, the slurries used in the past were greatly over retarded which contributed to the long and costly afterflow periods.

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