Trapped annular pressure mitigation: A spacer fluid that shrinks
J. B. Bloys, M. E. Gonzalez, J. Lofton, R. Carpenter, S. Azar, J. McKenzie, J. Capo, R. Hermes, R. Bland, R. Foley, F. Harvey, J. Daniel, F. Billings, I. Robinson and M. Allison
In deepwater or other sub-sea completed wells, fluids, usually 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 oil and gas, 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 (VIT) to limit heat transfer,6,7,14 nitrogen foam spacers yield highly compressible trapped fluids, crushable urethane foam insulation, etc. are somewhat successful, but are either very expensive, logistically troublesome or have unacceptable failure rates. This paper continues the discussion 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 20-40% of emulsified Methyl Methacrylate Monomer (MMA). Upon polymerization, the MMA phase shrinks by 20%...