Development and Installation of a High-Pressure-Rated Bridge Plug With Metal-to-Metal Sealing System

Abstract

This paper will describe the development, testing and installation of a high pressure rated mechanical bridge plug for a major oil and gas operator on the Norwegian Continental Shelf. Due to low reservoir pressure a mechanical high pressure rated bridge plug was required to be set as a zonal isolation barrier prior to a frac operation. The plug was set in a heavy wall liner with a 4.375?? ID, but had to pass a 3.725?? ID minimum restriction and hold 7500 psi differential pressure during the frac operation. The combination of high pressure rating and expansion ratio was a challenge to solve. A new metal-to-metal sealing technology was the solution to meet the required criteria. In July 2005, the first plug was successfully set, conveyed on coiled tubing. This new plug technology has improved the way of performing the zonal isolation and frac operation in low pressure reservoirs. History The development of the high pressure, high expansion metal-to-metal sealing system (Figure. 1) first started in 2000. The original goal was to develop a metal sealing bridge plug capable of achieving 10,000psi differential at 350 degrees F. The design concept of the sealing system relies upon the controlled application of load and pressure to expand the seal in order to create a fully formed pressure barrier with the inner diameter of the tubular into which it is being set. This development to date has resulted in a metal-to-metal sealing system employed primarily on well service type tools such as flow control devices, permanent and temporary wellbore plugging devices and straddle systems. With the need for high expansion occurring wherever a restriction (either planned or unplanned) exists above the depth at which intervention is required, it is plain to see that in traditional "bottleneck" type completions, the requirement for expandable sealing devices can be considerable. The discussed metal-to-metal sealing system has evolved since 2000 to a point where expansion ratios of up to 160% of its' original run in hole outside diameter (OD) are possible whilst at the same time being able to preserve the systems high-pressure, high-temperature (HPHT) characteristics. This expansion characteristic from a non-elastomeric seal is a desirable feature to have for applications that would have only been serviceable by inflatable type elastomeric devices. Other advantages offered to the operator in having a non elastomeric sealing system are in the opportunity to be able to eliminate some fairly commonplace oil and gas industry failure modes of seals such as; explosive decompression, gasification; temperature degradation; extrusion gap shearing; compression load failure and dynamic fatigue under pressure cycles. The development program centering on the evolution of the metal-to-metal sealing system has also seen the concurrent development of deployment and retrieval tools, allowing for the technology to be conveyed on common ‘live well’ deployment systems such as slickline, electric wireline and coiled tubing.