Trapped Annular Pressure Mitigation with a Shrinking Spacer Fluid
Recorded on July 31, 2012 (90 minutes)

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In deepwater or other sub-sea completed wells, fluids, usually cement spacers or drilling fluid, are commonly trapped in casing annuli above the top-of-cement and below the wellhead. When these trapped fluids are heated by the passage of warm produced fluids, thermal expansion can create very high pressures (10,000 -12,000 psi or more) and cause the collapse of casing and tubing strings.

Mitigation methods such as vacuum insulated tubing to limit heat transfer, nitrogen-based foam spacers to give highly compressible trapped fluids, crushable urethane foam, etc. are somewhat successful but are either very expensive, logistically troublesome or have unacceptable failure rates. This presentation discusses the development of a new approach which has created a water-based spacer fluid that will be used just ahead of the cement. The spacer contains perhaps 5-30% of emulsified liquid methyl methacrylate monomer (MMA). Upon polymerization, the MMA phase shrinks by 20%, creating room for the remaining fluid to thermally expand without creating catastrophic pressure. The polymerization is triggered by heat and a chemical initiator. The target temperature can be controlled by choosing an appropriate type and concentration of chemical initiator.  Premature polymerization during spacer placement can be prevented by an appropriate type, and amount, of inhibitor. This discussion covers the initial lab work, a mid-scale test-well trial and a full-scale land-based field trial of all the equipment and processes necessary to apply the technology in deep water.

The technology was jointly developed by Chevron, Los Alamos National Laboratories, Lucite International and Baker Hughes. 

Ben Bloys is the manager for Chevronís Technology Alliance with Los Alamos National Laboratories.  He also manages several University technology development programs.  Ben worked for 17 years at the ARCO Technology Center before joining Chevron in 2000.  He holds a BS degree in chemistry from Angelo State University (1984). He has 31 technical publications, 18 patents and is a member of SPE, AADE, ACS and API.