Expansion Charges: A Proven Localized Casing Expansion (LCE)-based Method

Localized casing expansion (LCE) technologies remediate annular fluid migration and restore zonal isolation integrity along pre-existing, annular cement sheaths. By imposing deformation on the innermost casing pipe to permanently enlarge its diameter, the associated annular volume reduction causes mechanical closure of defects such as micro annuli, fractures, and other voids in the annular cement and results in overall densification of the cement microstructure.

Axial sections of casing pipe that have been mechanically deformed by WT Bell Expansion Charges create roughly ring-shaped, radially outward protrusions or dents. The shape of these deformations depends on the casing grade, size, and weight. Preferably, dents should be placed in sets (triplets or other multiples) closely spaced over axial sections of casing pipe approximately 1 m to 2 m long. Over 80 successful deployments in onshore and offshore wells demonstrate a 94% success rate for sealing annulus leaks. On 6% of the wells, pipe expansion was successful but cement densification was insufficient to seal leaks. None of the success wells have shown integrity issues post-final abandonment.

Expansion Charge technology uses shaped charges on a standard tool string equipped with a casing collar locator, weight bar, two centralizers, and a shock sub deployed on a wireline or digital slick line. Developed in collaboration with a large international oil company and W.T. Bell International, Inc., the shaped charge configuration is tailored to create a pressure wave that causes plastic deformation and localized enlargement of the casing pipe without inducing material failure.

A casing collar locator (CCL) or a multi-finger caliper tool is often used to confirm that sufficient dent sets were placed at the planned depth. These logs also confirm that the casing diameter was enlarged at the dent positions. Bond logs can be run to evaluate the effectiveness of cement densification. Possible methods include one or several of the following indirect measurement methods. The absence of surface flow and pressure confirms that sustained casing pressure or vent flow has been remediated.

Extensive lab tests and long-term annular integrity monitoring post-expansion charge deployments in more than 50 wells have confirmed the reliability of the Expansion Charge LCE annular remediation method. WT Bell has performed extensive qualification testing to confirm the expansion limits on 4.5-in. to 20-in. casings.

WTBI Expansion Charges are proven to achieve maximum pipe expansion to remediate annulus leaks in plug-and-abandonment or live well operations while maintaining the treated casing's pressure integrity and load envelope. The efficient rigless operation remediates annulus leaks with a few wireline runs and reduces annular repair costs by up to 82% with much lower GHG emissions than conventional rig-based annular remediation techniques.