Schlumberger

Technical Paper: Cementing a production formation with low-fracture-pressure gradient in Wafra field, Kuwait

Society: SPE
Paper Number: 107047
Presentation Date: 2007
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Abstract

Achieving good zonal isolation in wells characterized by lost circulation has been a challenge in the Wafra field of Kuwait. The field is characterized by highly fractured formations with very low fracture-pressure gradients. In the Wafra field production intervals were commonly drilled with partial or complete losses, causing risk during drilling and cementing operations and damaging the producing formation. Also, uncemented columns of casing have developed leaks as a result of corrosive formation fluids. Two-stage cementing with extended slurries and top jobs were the common practices in this field in an attempt to circulate cement to surface. This technique delays the drilling progress, and the low mechanical properties of the extended slurries do not provide the required zonal isolation.

A new cementing program was introduced to combat lost circulation in this field. A slurry technology at a density of 900 kg3 (7.5 lbm/galUS) was used to cement the low-fracture-gradient production zone without cement losses or formation damage. Excellent set cement mechanical properties were achieved with very low set-cement permeability. In wells where high losses were expected, a surface-treated fiber was added to the cement to bridge across the problem zone. This paper presents case histories study of several wells, laboratory designs, and field data in which these new techniques successfully treated partial to complete losses encountered during cementing operations. In all jobs using the new slurry, lost circulation problems were cured and cement was circulated to surface.

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