Deepwater wells face a myriad of challenges, amongst which are: narrow pore pressure-fracture gradient margins, salt sections and salt exits, cementing operations in relatively weak formations, management of annular pressure buildup (APB) in un-cemented annuli and well integrity assurance for life of well. New methodologies and a novel new stage cementing system has been developed to address these challenges.

In a recent Gulf of Mexico well, a 16" liner primary cement job secured the bottom of the section but did not cover sufficient height of the salt section to provide adequate zonal isolation and created an APB issue. A planned second stage cementing operation was performed using a new cementing valve that was tested to the same gas-tight regime as the V0 specification employed in ISO14310. Two cementing valves were run on the 16" liner string; one at the top, immediately below the liner hanger and one near the bottom. A drillpipe deployed cementing tool was RIH to shift the upper cementing valve open and pump a large quantity of cement down the annulus from the liner hanger to the top of cement left by the primary cement job; the upper valve was then closed and tested. Further operations, including logging verified the cement job integrity.

The paper will discuss the operation in detail and explain how performing a second stage cementing job "top-down" through a cementing valve, as opposed to conventional cementing circulation, resulted in full zonal isolation throughout the entire section; and eliminated many of the issues described before. The paper will present additional benefits such as fully filling the liner annuli to eliminate APB and improve well integrity for life of well. There will be an evaluation of future opportunities to improve zonal isolation in salt sections; create secure wells in areas of depleted sands; and access narrow margin areas of interest with low pore pressure-fracture gradient.

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