Recent Developments In Packer Seal Systems For Sour Oil And Gas Wells
Authors: Burley J.D. , Holland W.E. 
Published: December 2007

Severe limitations in existing packer seal systems have caused operational problems in sour oil and gas wells in Jay, problems in sour oil and gas wells in Jay, Florida area fields. Commonly used elastomeric materials and seal designs undergo serious chemical and physical alteration in the sour environments. These changes result in packer seals which deteriorate, seize, and are subject to leakage at high temperature and pressure. With this performance background, a program was undertaken to evaluate seals not only for Jay type wells but also for higher temperature deep, sour gas wells (DSGW).

This paper describes laboratory evaluations of materials, design innovations, and field tests used to develop reliable seals for deep, sour wells.

Introduction

The search for new reserves has resulted in drilling and completing deeper wells in increasingly hostile environments. This activity with its attendant problems due to sour formation fluid, high pressure, and high temperature requires extension of current technology to meet new generation well conditions. One particular development need is a reliable downhole packer seal system that can function in hot, high pressure sour gas for an extended well completion pressure sour gas for an extended well completion life.

Target design conditions established for DSGW packer development are extremely severe, including 23,000 feet total well depth, bottomhole pressure in excess of 22,000 psi, and 450 deg. F bottomhole temperature. Production containing 35 percent H2S, 15 percent CO2, with the remainder mostly methane and some possible water contamination was forecast. possible water contamination was forecast. Review of these anticipated conditions with major packer manufacturers showed none had equipment that could be recommended for such harsh service. There were no available packer seal designs that could withstand the packer seal designs that could withstand the environment and contain expected pressure differentials to 15,000 psi at 450 deg. F.

Not only were available packer seal systems unsuitable for extreme DSGW conditions, but they were also found to be deficient for much less severe conditions. Commonly used oil and gas well packer seals had been found to undergo serious chemical and physical deterioration in Jay, Florida area wells from the combined influence of stress, sour fluids, and temperatures up to 300 deg. F. This deterioration resulted in leaking seals, corroded metal packer components, and seals stuck so tightly into the packer bore that tubing could not be pulled free during a majority of well reconditioning jobs.

Evaluation of various seal materials and designs was undertaken to determine which would be most suitable for use in deep, sour gas well packers. Testing was conducted in a simulated hot, sour gas well environment. The candidate materials were tested in a 2.750 × 2.375-inch vee seal configuration for application as inner, tubing-to-packer seals. The outer, packer-to-casing seals were tested in 5-1/2-inch, 20 lb./ft. casing size cylindrical style compression elements.

Specific objectives of this development program were: program were: 1. To test various elastomeric type materials and determine which are most resistant to hot, sour gas well fluids.