Downhole well integrity starts by removing the drilling fluids from the well and cleaning the annulus using a spacer to prepare for the cement to be placed. The Kamose field in the Egyptian Mediterranean Sea is drilled with a diesel oil-based drilling fluid system that is very difficult to remove with conventional spacer technologies. To improve the mud removal, an innovative spacer based on fiber scrubbing technology was used successfully.

The Kamose wells are drilled with high deviation that varies from 60˚to75˚ resulting in poor mud removal due to insufficient casing standoff. The narrow windows between pore pressure and fracture gradients limits the pump rate and thus results in the unsuccessful use of conventional spacers. This results in a mud layer that is always left in the narrow side of the well, which impacts the log response and the downhole well integrity. To address the issue, an innovative mud removal solution was developed. The spacer design includes an engineered scrubbing material which, through mechanical action, cleans the surfaces of the casing and the formation. This allows for better contact of the cement with the casing, formation surfaces, and bonding.

Extensive laboratory qualification tests with the current drilling fluids were performed not only to check the cleaning efficiency of the new spacer but also on the compatibility with all the other fluids. The results show a very high cleaning efficiency of 90% compared to 68% when using a conventional spacer. The solution was combined with the local cementing best practices which produced an excellent log response using sonic and ultrasonic tools therefore ensuing the downhole well integrity.

The case history of the spacer fiber-based technology solution provides an alternative to improve the cement bond evaluation and ensuring downhole well integrity.

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