This paper discusses the advantages that accrue to remedial operations as a result of using coiled tubing to enable the fast and safe removal of the latest-generation composite bridge plugs in an underbalanced environment. The paper addresses the development and early field history of latest-generation composite bridge plugs, which are designed to set securely in the casing and then be easily removed using coiled-tubing-conveyed downhole motors and drilling tools in an under-balanced environment after remedial operations are complete.
The new technology is particularly applicable in multi-zone, commingled gas wells with varying bottom-hole pressure, where there is a need to reduce overall operator expense and minimize formation damage, without compromising reliability of safety.
Field experience verifies that a reliable and easily removable composite bridge plug requires substantially less rig time than conventional cast iron bridge plugs while at the same time reducing formation damage. These benefits result from the ability of coiled tubing conveyance to eliminate the need for kill weigh fluid and to enable the well to be worked over "live".
The paper includes a listing with brief descriptions of more than 100 field runs to date for zonal isolation and treatment using this new technology (see Figure 1). It also examines in detail the following two case histories:
Phillips Davis Lease Well #8 in Louisiana's Webster Parish
Marathon's J. Kaye Field Well #3–33 in Oklahoma's Grady County.
Since the introduction of composite bridge plugs onto the market in 1992, composite technology and design has substantially advanced plug performance over the years. However, operators still have complaints about current composite bridge plugs on the market. Operator complaints about the current composite bridge plugs are identified as:
the plug moves after being set,
metallic debris left in the well after drill up,
the need of a cement cap for high pressure applications,
lack of performance and reliability,
very short life span as related to pressure integrity,
tungsten carbide buttons and brass rings cause drill up difficulties and damage drilling tools along with casing.
The second generation composite bridge plug is designed to address operators' concerns related to existing composite bridge plugs. The second generation composite bridge plug's design dramatically improves performance through major innovation in design and materials developed in response to input from operators.