Retrievable Bridge Plug
A retrievable bridge plug is a temporary downhole pressure isolation device that is set across the casing or liner bore at a specified depth to create a mechanical barrier between the formation below and the wellbore above, and that is designed to be retrieved from the wellbore after its temporary function is complete without drilling or milling, using a pulling tool run on wireline, slickline, or coiled tubing to engage the plug's fishing neck and mechanically release the anchoring slips and packing elements before pulling the plug to surface; retrievable bridge plugs are used in well intervention and workover operations to temporarily isolate specific zones for pressure testing, fluid displacement, well killing, perforation of new zones while protecting existing perforated intervals, acid or stimulation treatments of specific intervals, and for setting up multi-zone production tests in wells with multiple perforated intervals; the retrievable bridge plug is distinguished from the permanent or drillable bridge plug (which is permanently set and must be drilled or milled out after use, requiring a separate drill-out trip that adds cost and time to the operation) by the ability to be mechanically released and pulled from the wellbore intact, and from the cement plug (which is a mass of set cement placed across the wellbore that must be drilled out and cannot be retrieved) by the mechanical rather than cementation sealing mechanism; retrievable bridge plugs are manufactured in a range of casing sizes (from 2-3/8 inch tubing to 13-3/8 inch surface casing) and pressure ratings (from 3,000 to 10,000 psi differential pressure rating for typical production well service), with the specific design selected based on the casing ID at the setting depth, the maximum differential pressure to be held, and the maximum wellbore temperature at the setting depth.
Key Takeaways
- Retrievable bridge plug setting mechanism uses a combination of hydraulically or mechanically actuated slip elements (hardened steel anchoring slips that bite into the casing wall to resist axial movement) and an elastomeric or mechanical packing element (that seals the annular space between the plug body and the casing ID) to create a bidirectional pressure seal at the plug setting depth: wireline-set retrievable bridge plugs use the energy of an explosive setting tool (a jet or percussion firing head) to drive the setting mandrel against the plug body, compressing the packing element and setting the slips against the casing wall in a single mechanical stroke; hydraulically set retrievable bridge plugs use the pump pressure applied through the tubing or workover string to actuate a hydraulic cylinder that drives the setting mandrel; mechanically set plugs use weight and rotation of the setting tool to engage the plug setting mechanism; after setting, the integrity of the bridge plug seal is typically confirmed by a pressure test (applying pressure above the plug from the wellbore above and monitoring for stabilization or decline that indicates whether the plug is holding pressure or leaking), with the pressure test pressure and hold time specified in the well program based on the anticipated maximum wellbore pressure differential during the planned operation above the plug.
- Retrievable bridge plug retrieval mechanism requires the engagement of a pulling tool with the plug's fishing neck (a standardized cylindrical section at the top of the plug designed to be caught by an overshot or by locking lugs on the retrieval tool), followed by a mechanical release that disengages the anchoring slips from the casing wall and decompresses the packing element before the plug is pulled uphole: the release mechanism on most retrievable bridge plugs is a shear-pin or locking-sleeve design in which a specific upward pull load (the release load, typically 10,000 to 30,000 pounds above the plug weight) applied by the pulling tool shears the release pins or moves the release sleeve to a position that allows the slips to retract and the packing to decompress; if the mechanical release fails (which can occur if the plug has been set for an extended period at high differential pressure that has caused the packing element to take a compression set, or if the slip teeth have embedded too deeply in the casing wall), the fallback retrieval method is to apply higher overpull loads in stages to attempt to free the plug, and if that fails, to jar the plug upward using a wireline or coiled tubing jar assembly to deliver impact loading that may dislodge a stuck plug that could not be pulled free by steady tension; if the plug cannot be retrieved by pulling and jarring, it must be milled out using a packer mill run on coiled tubing or workover drillpipe, converting the retrievable plug into an effectively permanent obstruction that must be drilled through rather than mechanically released.
- Retrievable bridge plug selection for high-temperature and high-pressure (HPHT) wellbore conditions requires plug designs with thermally stable elastomeric packing elements that maintain their sealing properties over the anticipated temperature range, and with slip and body materials that retain adequate mechanical strength at elevated temperatures to resist deformation under the high differential pressure loads encountered in HPHT well service: standard retrievable bridge plugs with nitrile or neoprene packing elements are rated for temperatures to approximately 150 to 180 degrees Celsius, with the upper limit set by the softening and degradation of the elastomer at elevated temperature that reduces its ability to maintain the required contact pressure against the casing wall; high-temperature retrievable plug designs use perfluoroelastomer (FFKM) or hydrogenated nitrile (HNBR) packing elements rated to 200 to 230 degrees Celsius, and may also use metal-to-metal seal elements (backup metal seals that engage when the elastomeric primary seal softens at extreme temperatures) to maintain sealing integrity in HPHT conditions; the differential pressure rating of retrievable bridge plugs in HPHT service must be derated from the room-temperature rating to account for the reduction in slip and packing contact force at elevated temperature, and the derating factor is provided by the plug manufacturer based on qualification testing at the target temperature and pressure.
- Retrievable bridge plug applications in multi-zone well testing and completion operations include the setting of a retrievable plug below each new perforation interval to isolate it from existing perforations below while the new zone is tested and potentially stimulated, followed by plug retrieval to commingle the production from all perforated intervals: in a well with multiple stacked productive formations, the typical workover sequence for adding a new zone above existing perforations involves setting a retrievable bridge plug just below the lowest existing perforation, perforating the new zone above the plug, pressure testing the new zone's casing integrity, and optionally acid-treating or fracture stimulating the new zone while the plug protects the existing perforations from the treatment fluids; after the new zone treatment is complete and the well is cleaned up, the retrievable plug is retrieved to allow production from the new zone to commingle with the existing production through the wellbore; in wells where zonal commingling is not desired (for regulatory compliance, for allocation metering, or because the zones have very different pressures), the retrievable plug may be replaced with a permanent packer with a sliding sleeve to provide selective zone control during production.
- Retrievable bridge plug inventory management and compatibility verification are critical operational steps before any plug setting job because retrievable bridge plugs are manufactured in specific casing ID ranges, and deploying a plug that is too small for the casing ID (which will not develop adequate slip contact force to anchor against the casing wall) or too large for the casing ID (which may jam during run-in before reaching the setting depth) will cause the operation to fail: the casing ID at the setting depth must be verified against drift records (the drift run that confirms the minimum inside diameter of the casing string) rather than the nominal casing ID, because casing coupling ID restrictions, scale buildup, damage deformation, and collapsed or buckled sections may reduce the actual drift ID below the nominal casing ID; the plug size is selected based on the minimum drift ID at the setting depth, with the plug's OD in the unset position (the run-in OD) at least 1/16 to 1/8 inch smaller than the measured drift ID to allow passage through all restrictions above the setting depth; the pressure and temperature ratings of the selected plug must exceed the maximum anticipated wellbore conditions during the operation by the appropriate safety factor specified in the well program, typically 25 percent above the maximum anticipated differential pressure and 10 degrees Celsius above the maximum anticipated temperature.
Fast Facts
Retrievable bridge plugs became a standard tool in production workover operations during the mid-twentieth century as the oil industry recognized that the ability to temporarily isolate zones during workover without committing to a permanent plug dramatically improved the flexibility and economic efficiency of well intervention programs. The development of reliable elastomeric packing materials that could seal against high differential pressures and be mechanically compressed and released multiple times without losing their sealing properties was the key technical advance that made the retrievable bridge plug practical, and the ongoing development of high-temperature elastomers continues to extend the application range of retrievable plugs into increasingly demanding HPHT well environments.
What Is a Retrievable Bridge Plug?
A retrievable bridge plug is a mechanical device set in the casing bore to temporarily seal off the wellbore below it, creating a pressure barrier that allows work to proceed safely in the wellbore above without fluid entry from the zone below, and that can be pulled out intact when the isolation is no longer needed. The retrievable plug anchors to the casing wall with hardened steel slips, seals the annular space with a compressed elastomeric packing element, and holds pressure differentially until the job above it is done. When retrieval is required, a pulling tool engages the plug's fishing neck, applies an upward load that releases the slips and decompresses the packing, and pulls the entire assembly to surface without drilling. This recoverability is what makes the retrievable plug preferable to a cement plug or permanent drillable plug in workover operations where the isolation is temporary: there is no drill-out trip, no debris to clean up, and no permanent restriction left in the casing. The plug goes down, does its job, and comes back up, leaving the wellbore in the same condition as before the operation.
Synonyms and Related Terminology
Retrievable bridge plug is also called a packer bridge plug, retrievable packer, or simply a bridge plug (when context makes the retrievable nature clear). Related terms include bridge plug (any downhole device set across the casing bore to create a mechanical pressure barrier between the wellbore above and the formation or completion interval below, available in retrievable designs that can be pulled intact and in permanent or drillable designs that must be milled out after use), setting tool (the downhole assembly run above the bridge plug on wireline, slickline, or coiled tubing that provides the mechanical energy to compress the packing element and set the anchoring slips against the casing wall, using explosive, hydraulic, or mechanical energy sources depending on the plug design), packer mill (a downhole milling tool run on coiled tubing or workover drillpipe to drill through a stuck or permanently set bridge plug or packer that cannot be retrieved by pulling, removing the obstacle by mechanical cutting rather than mechanical release), differential pressure (the difference between the pressure above and below the bridge plug, which the plug must hold across its packing element and slip system to maintain zone isolation, with the plug's pressure rating specifying the maximum differential it can safely contain without leaking or displacement), and isolation packer (a packer device set in the casing or wellbore to isolate one zone from another by anchoring to the tubular wall and compressing a sealing element against it, functioning similarly to a bridge plug but typically used in the context of production tubing isolation between two perforated intervals rather than full wellbore isolation).