ABSTRACT:

The challenge of cementing production strings across depleted, low-pressure reservoirs is probably well known and yet ineffectual in many cases. The general well condition just before cementing the liner includes losses, minimal mud circulation to condition the hole, and almost no pipe movement for mud removal. Compound these issues with high bottomhole temperature (>230°F), a deep well (>10,000-ft TVD), and oil-based mud (OBM) (used to drill the section) and the chances of succeeding become negligible. This paper presents a case history of this type for an ultra-lightweight cement application in a deep (14,720-ft MD) and relatively hot well (270°F) in the Gulf of Suez (GOS) area. The formation fracture gradient (FG) for this well was estimated to be below 7.8 lb/gal because oil-based mud was being lost at 20 bph with this weight. Yet the goals for the cementing job were the same as for other production wells:

  1. Achieve good zonal isolation1

  2. Experience minimal damage to production zones

  3. Several prospective layers spread over 450 ft of drilled section

  4. Experience no non-productive time (NPT)

The cementing challenge was tremendous and required the use of multi-stage tools and lightweight slurries to remain below fracturing limits. Cementing best practices had to be closely followed to help ensure that a good bond would be obtained in the OBM environment. The slurry design evolved through several optimization stages until a well-suited final blend was found for the job. Finally, the post-job cement bond log showed excellent bonding to the formation and pipe and delivered a competent wellbore for production

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