How Challenging Well Conditions Hindered Frac Plug Drillouts
An operator deployed 2-inch coiled tubing (CT) to drill out composite frac plugs following a well stimulation from 13,000 to 17,580 feet. Outdated cleanout techniques utilizing gel sweeps and high concentrations of friction reducer had saturated the fluid system in polymer, increasing viscosity and decreasing cleanout efficiency.
Upon reaching the 26th plug at 16,528 ft., the motor locked in a stalled condition, resulting in loss of circulation and a stuck CT string. Since pumping down a cutting tool was not possible, wireline cut the stuck CT at the kick off point, leaving 4,528 ft. in the well. With a shut-in wellhead pressure of 6,000 psi, various fishing alternatives (e.g. a workover rig, a snubbing unit, and other alternative methods) were ruled out.
How a Hybrid Approach Resulted in Dramatic Savings in Time and Cost
As a solution, Nine Energy Service proposed a unique hybrid strategy using a combination of a rig-assist snubbing unit, slickline, and coiled tubing. The well was loaded with CaCl2 fluid to reduce wellhead pressure and minimize risk. A rig-assist snubbing unit rigged atop the coiled tubing BOPs in order to run a 2 7/8-inch workstring with fishing BHA to latch the 2-inch CT fish. The workstring and fish were pulled into tension, providing a conduit to the CT fish.
An initial wash run using 1 1/4-inch CT was made, running through the 2 7/8-inch workstring and into the 2-inch fish. A pressure-actuated radial jet cutter was then run to friction lock-up depth of 14,925 ft., cutting the 2-inch CT string. The 1 1?4-inch string was pulled out and rigged down. The rig-assist snubbing unit pulled the 2 7/8-inch workstring out of the well and hung the 2-inch CT fish in the surface BOP’s. Slickline set two bridge plugs at the bottom of the fish for wellbore isolation. Finally, a 2-inch CT unit made the connection to the fish and spooled 3,000 ft. from the well without incident.
The entire operation was completed in 18 days with no HSE incidents and saved the operator more than 55 days and approximately $4 million. More than half the wellbore was returned to production clear of obstructed flow.
Visit nineenergyservice.com/coiledtubing or Booth #19 at the SPE ICoTA Well Intervention Conference for more information.