You’re facing a live well and need to perform critical maintenance or repairs on surface equipment – perhaps a BOP stack swap or a wellhead component replacement. Killing the well might be an option, but it adds time, cost, and potential formation damage. What you need is a robust, temporary downhole barrier that provides verifiable isolation, allowing you to work safely above, yet can be retrieved cleanly when the job is done. This is where a retrievable packer, specifically an RTTS (Retrievable Test-Treat-Squeeze) packer, combined with a subsurface control valve (SSCV) – often called a storm valve – becomes indispensable.
The challenge isn’t just installing a packer; it’s installing a complete dual-barrier system that you can trust. The RTTS packer provides the annular seal, isolating the casing, while the storm valve seals the workstring’s internal bore. Together, they create a reliable isolation point, allowing you to unlatch and POOH with the upper workstring, leaving the well secured. But getting it right demands meticulous planning and execution, especially when dealing with live well conditions or tight operational windows.
Why the Dual Barrier Approach Matters
Relying on a single barrier for critical well isolation, especially for operations like BOP repairs, is an unnecessary risk. A retrievable packer alone isolates the annulus, but the workstring itself remains a conduit to the formation. By integrating a storm valve directly above the RTTS packer, you create a verified two-barrier system. The packer holds the annulus, and the storm valve holds the tubing bore, effectively isolating the well below your intended point of work. This setup provides the confidence to break out the workstring above the storm valve, knowing the well remains secure.
The storm valve typically features a shear-pin activated plug at its base and a sliding sleeve mechanism. When deployed, the plug provides initial bore isolation for pressure testing the packer and the valve itself. Once isolation is confirmed, the sleeve can be closed, and the workstring detached. For operations requiring full bore access, like bullheading kill fluid in a well control scenario, the shear plug can be expelled to the rat hole by applying sufficient pressure, assuming no downhole restrictions prevent it from falling clear.
Operational Approach: Running and Setting the Assembly
Before you even pick up the BHA, ensure a bit and scraper run has been made to clean the casing ID. Skipping this step is a common cause of packer elements failing to set or seal properly, and it requires a formal Management of Change (MOC). If you’re on a semi-submersible, a slip joint in the string above the storm packer is non-negotiable to manage heave. Always use rig tongs for making up tool joints; iron roughnecks can easily crush the critical components of the BHA.
The BHA typically consists of the RTTS packer at the bottom, with the storm valve directly above it. A 10ft pup joint above the storm valve facilitates handling. Function test the packer’s drag blocks on the rig floor to ensure smooth operation before running in hole. Calculate your target hang-off weight carefully. This is the weight required to keep the packer set, factoring in buoyancy. For example, if you need 30,000 lbs on the packer in fluid, and your buoyancy factor is 0.8671, you’ll need approximately 35,000 lbs in air to achieve that. This weight must be accurately slacked off on the packer during setting.
Make up all connections using the specified torque values – typically around 20,000 ft.lbs for IF connections and 2,000 ft.lbs for service joints. Crucially, the connection on the seal mandrel should be hand-tight and then backed out by one thread. This allows for the required rotational movement during setting and closing the storm valve. RIH slowly, especially when passing through restrictions like the wellhead or liner tops, to prevent damage to the packer elements. Never run the packer across perforations, casing joints, or couplings, and avoid tagging bottom with the packer.
Once at your desired setting depth (e.g., 984ft/300m), break circulation at 2-3 bpm and reciprocate the workstring +/- 7ft around the setting depth to ensure the wellbore is clear. Pick up to the setting depth, make 2-3 right-hand rotations (adjusting for well deviation – typically ¼ turn per 1000 ft), and then slack off the calculated hang-off weight (e.g., 35,000 lbs) onto the packer. Monitor the weight indicator for a positive indication that the packer has set and is taking weight.
With the packer set, pressure test the annulus above the packer to the client’s specification. A successful test verifies the annular seal. Bleed off annular pressure, then ensure the storm valve is in a neutral position by slacking off the exact hang-off weight. Mark the workstring vertically. Make 22 left-hand rotations, easing off the brake to prevent thread torque, to back out the seal mandrel from the storm valve. This closes the sliding valve. Pick up the workstring by 10ft to confirm the seal mandrel is clear of the storm valve. Finally, pressure test the top of the storm valve. Remember its shear pin is rated for roughly 3,000 psi. Always factor in hydrostatic pressure (e.g., 445psi at 984ft) and use 80% of the shear value (e.g., 2,400 psi) as your max applied surface pressure. For this example, that’s about 2,000 psi surface pressure. A successful test means you have dual-barrier isolation. You can now POOH with the workstring above the storm valve.
Retrieval Procedure and Contingencies
When it’s time to retrieve the assembly, RIH with the seal assembly. If running in casing larger than 10-3/4″, use a centralizer to ensure proper alignment. At approximately 10ft above the storm valve, break circulation at 2 bpm. RIH slowly, tagging the top of the storm valve with 3-5 KIPs. Watch for a weight reduction and a pressure increase in the workstring, indicating you’ve landed in the valve. Stop circulating, apply 500 psi to the workstring, and make 22 slow right-hand rotations. Monitor torque, ensuring it doesn’t exceed 2,000 ft.lbs. Around the 11th rotation, the sliding valve should open, and you’ll see pressure equalization in the string. Complete the remaining rotations.
Once the valve is open, proceed to un-sit the packer with a straight pull on the workstring. Once released, flow check and wait 10 minutes for the packer elements to relax before POOH. If the packer is difficult to un-sit, apply annular pressure to help equalize forces and retract the hydraulic slips. This is a common and effective contingency.
Decision Checklist for RTTS & Storm Valve Operations
- Pre-Job Planning:
- Bit and scraper run confirmed? MOC if omitted.
- Slip joint planned for semi-sub rig?
- Rig tongs specified for tool makeup?
- Shear pin values and hydrostatic pressures calculated? Max surface test pressure defined?
- Hang-off weight (in fluid and air) calculated and verified?
- Max circulation rate through storm valve (e.g., 5 bpm) communicated?
- Ported sub included below packer for equalization (if available)?
- Running In Hole:
- RIH speed reduced at restrictions (wellhead, liner tops)?
- Packer not set across perforations, casing joints, or tagged bottom?
- Seal mandrel backed out by one thread?
- Drag blocks function tested on surface?
- Setting and Testing:
- Workstring reciprocated at setting depth?
- Correct number of right-hand rotations for setting?
- Exact hang-off weight slacked off?
- Annulus pressure test successful?
- 22 left-hand rotations for storm valve closure?
- Storm valve top pressure test successful (within shear pin limits)?
- Retrieval:
- Centralizer used for large casing sizes?
- SSCV tagged with correct weight (3-5 KIPs)?
- 22 right-hand rotations for opening? Torque monitored?
- Packer un-sat with straight pull?
- Annular pressure contingency ready for difficult un-sit?
Failure Modes and Lessons Learned
Even with meticulous planning, things can go sideways. A common issue is the RTTS packer pre-setting while running in hole, often due to excessive RIH speed or hitting an obstruction. If this happens, pick up the workstring a few feet, make 2-3 left-hand rotations to un-set, and then continue RIH more slowly. If the packer sets but fails to seal during the annulus test, unset it and try setting at a slightly different depth. This could be due to setting on a casing collar, debris, or a minor casing imperfection.
The storm valve’s shear pin is a critical safety feature, but it also presents a limitation. If you need to bullhead into the well, you must apply enough pressure to shear that pin (e.g., 2,555 psi in our example) to expel the plug and gain full bore ID. However, never expel the bull plug if there are downhole completion accessories or ID restrictions below the packer that could prevent the plug from falling clear. You’ll end up with a fishing job on your hands. Always confirm the rat hole is clear before planning to shear the plug.
During retrieval, a packer refusing to un-sit is frustrating. Before resorting to extreme over-pull, try applying casing (annular) pressure to help retract the hydraulic slips and equalize differential pressures. This often works. Finally, in any well control scenario, if you experience a well kick or flow while setting or retrieving, immediately equalize pressure across the assembly and conduct a proper flow check before proceeding. If available, a ported sub directly below the RTTS packer can greatly aid in safely equalizing tubing and annular pressures during un-setting or in a well control event.
Bottom Line
Deploying a retrievable packer and storm valve assembly is a high-stakes operation that demands precision. Follow pre-job recommendations, adhere to calculated parameters, and have your contingencies ready. Dual-barrier isolation is paramount for safety and operational flexibility.
Have a question about your well? Reach out via the contact page.