Schlumberger

Technical Paper: Cementing Deepwater, Low-Temperature Gulf of Mexico Formations Prone to Shallow Flows

Society: SPE
Paper Number: 87161
Presentation Date: 2004
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Abstract

Shallow gas and water flows are a major concern when cementing deepwater wells in many Gulf of Mexico fields, often requiring expensive remedial work, premature well abandonment and re-spudding. Entire templates can be compromised if a single cement job on surface pipe fails to provide zonal isolation from the shoe up to the mud line.

Traditionally, compressible fluids (mainly foamed cements containing nitrogen) have been used to mitigate shallow-flow hazards in the Gulf of Mexico. The disadvantages of these systems include safety concerns, complicated logistics, lack of reliability, placement problems, and lack of confidence in long-term cement integrity.

As an alternative to standard energized fluids, special cementing systems based on packing volume fraction and ratios of sized particles (particle-size distribution or PSD systems) have been used with success in water depths exceeding 6,000 ft in the Gulf of Mexico. This paper provides case histories and discusses the use of these innovative systems for deepwater situations. These systems are specially designed to provide optimized gel and compressive-strength development in low-temperature environments while allowing the thickening time to be tailored to any wellbore geometry. Slurry volumes from 1,500 to 2,500 bbl have been pumped without incident. The intrinsically low permeability and porosity of these systems at both the slurry and set-cement stages provide resistance to external attacks and influx of water or gas. In addition, these systems are tested and pumped using standard equipment, completely avoiding the complications of energized fluids; extra personnel are not required.

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