The customer had been milling frac plugs with coil tubing in their south Duvernay field with 12,500psi BHP. While performing a wiper trip, coil tubing had become stuck. And while working the string, it parted where the string weight tapered. Remaining coil pulled out of hole, well was secured with 7,000psi at surface.
Piston, the customer and Weatherford Fishing developed a plan to retrieve the coil. The BOP stack was designed to ensure a backup for every ram, and the ability for holding the coil string in slip rams once the coil was retrieved so that it could be reeled out of the well. 12 BOPs were used in the stack. A 2-7/8 SLH90 drill string was chosen and profiles were built for 1.781 R in the drillpipe thread. An overshot with high pressure packoff was chosen for latching the coil so that it could be circulated. The first run was to dress the fish top and approximately .5m was removed. The high pressure packoff was then snubbed in the well and attempted to be rotated on. The fish started moving down across the lateral and the grapple was scrubbed. After two more attempts to grab the floating fish were unsuccessful, the well was flowed to lockup the fish with sand. Fears were that if the fish top got pushed into the 4-½ liner, fishing would become more difficult. With sand locking up the fish, it was grabbed and circulated free through TKR plugs in the profiles. The fish was then pulled to 1000m from surface, wireline was rigged up and plugs were pulled. Wireline attempted entry into the fish and failed. A 4-1/16 coil unit was rigged up on top of the drillpipe, and 1.25 coil was run and cleaned out the fish ID. Wireline was then run inside the coil and the coil was perforated just above the mha. Slickline plugs were set inside the drillpipe and the plan was to run the string back to TVD and kill the well. The string would not move because a hydrate had formed while rigging out coil/ slickline. Coil was rigged back up and run inside the drillstring to warm the pipe from 1000m to surface for 3 days until the annulus could be freed of hydrate. A 50/50 methanol-water mixture was then bullheaded down the annulus. Coil was rigged out again and the string was lowered to place the perforations in the coil at 4200m MD. Slickline was rigged in and the plugs removed from the string. 2000 kg/m3 oil-based mud was circulated then weighted up to 2200kg/m3 to kill the well. After ensuring the well would remain static, a 2600 kg/m3 pill was pumped into the drillpipe to allow it to drain. The string was then pulled to surface. Coil tubing was secured in the slip rams, and the jack/ work window removed. The injector was hoisted above the fish and a dimple-to-dimple connection was installed, and the injector was bolted to snubbing BOPs. The connector was pull tested, slip rams were opened and coil reeled the connector to just above the reel. ½” chains were welded along the connector in case the connector caused the coil to snap on the reel. Coil was then reeled out of the well.
All coiled tubing equipment was rigged out and the snubbing jack rigged back in. A mill, mud motor, agitator and dual bpv’s were run in the well with a 2-3/8 CDS pac drillpipe string, then crossed over to 2 7/8 SLH90. At the heel, the oil-based mud was circulated out of the wellbore and the string was run into the lateral. Remaining plugs were milled, the drillstring was snubbed out of the hole and the completion string was snubbed and landed.