Reliable Completion Systems for Gas Migration Prevention

Abstract

Long String completion systems will be presented for prevention of gas migration composed of an annular casing packer with remote-set technology activated by a cementing wiper plug (CWP) with a magnetic array or an acoustic wave generator. Proven and reliable zero-extrusion gap element technology provides a gas-tight annular seal while reliability is enhanced by eliminating all communication ports and potential leak paths between the packer inner diameter (ID) and casing annulus. There are three main benefits of these systems. They provide a reliable mechanical barrier to "flow after cementing" which can result in a significant financial impact to the operators and their service providers. They reduce / eliminate issues with annular casing pressure (ACP) and sustained casing pressure (SCP). They also provide a permanent seal between casing strings, reducing the risks of costly plug and abandonment (P&A) operations. During cementing operations the packer is activated by the CWP. Downhole sensors detect the magnetic field generated by the CWP and initiate the setting sequence of the packing element. Another system employs an acoustic wave generator at the rig floor to initiate the setting sequence in shallow-depth applications. An optional contingency setting sequence can be programmed prior to deployment and can be deactivated remotely if required. Design and qualification of these systems will be discussed along with available field installation data. Three systems are currently awaiting field trials. Industry standards are focused on reducing annular flow prior to, during, and after completion of primary cement jobs. While these changes will improve annular isolation, conventional cementing contains fundamental limitations that complicate control of shallow gas hazards and water flows. The US Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) has thus identified "flow after cementing" and SCP as potential hazards. The above completion systems will help alleviate these concerns. It is noted as of October-1-2012, BOEMRE has been replaced by the Bureau of Ocean Energy Management (BOEM) and the Bureau of Safety and Environmental Enforcement (BSEE).

Successful Installation of a Completion System for Gas Migration Prevention

“…The pattern is unique from any other vibration that is generated during normal operations, thus preventing inadvertent activation of the packer during the trip downhole or during cementing operations 5 . As a contingency measure, if the trigger signal is not detected, a pre-programmed timer in the downhole electronics can activate the system without intervention.…”