Wellbore Cleaning for Abandonment Operations CGII Site Operating Procedures

Regulators are asking for clean wellbores ahead of cut and cap operations to protect the base of groundwater from migrating oil, reduce wind-wicking of oil from recovered production tubulars on the lease/equipment, and limit the potential for surface water to displace oil from the well after a vented cap is installed.

• This process was developed over 10 wells at 765 m (2,510’) TVD with 177.8 mm (7”) casing, 88.9 mm (3.5”) tubing, 25.4 mm (1”) rods, and 10 API oil.
• 1 tote equates to 1,000 L or 275 gallons.
• Tend to Corporate Health, Safety, and Environmental requirements.
• Move in and rig up a service rig with auxiliary support equipment.
• Record and bleed off the shut-in tubing and casing pressure.
• Unseat the rotor from the stator or the insert pump from the PSN.
• Mix 0.5 tote of CG-100 with 2 totes of 85°C (185°F) hot fresh water in a pressure truck (herein referred to as mixed fluid).
• Pump 1 tote of mixed fluid down the tubing string and 1.5 totes of mixed fluid down the tubing-to-casing annulus.
• Tubing ID Displacement: Chase the mixed fluid with a tubing volume (~4 totes) of 85°C (185°F) hot fresh water.
• Annulus Displacement: Chase the mixed fluid with an annular volume (~12 totes) of 85°C (185°F) hot fresh water.
• Surface tubulars (inspecting if required). Run a casing scraper on tubing compatible with the production casing inner diameter to the top perforation. Surface the casing scraper.
• Set a tubing conveyed permanent bridge plug (PBP) as required by regulatory requirements above the perforations.
• Mix 0.5 tote of CG-100 with 2 totes of 85°C (185°F) hot fresh water in a pressure truck (herein referred to as mixed fluid).
• Pump a 2 tote 85°C (185°F) hot fresh water spearhead down the tubing-to-casing annulus.
• Chase the spearhead with the mixed fluid and a hole volume (~17 totes) of 85°C (185°F) hot fresh water.
• The rate appeared effective at 400 – 500 L/min (2.5 – 3.1 bbl/min). Monitor the returns at the rig tank. Depending on production chemicals, results have included:
  • Oil, chased by a light brown foamy fluid.
  • Foamed water transitioning to a mild brown shaving cream (on MEOR or polymer wells).
  • Straight hot fresh water.
• Continue to circulate until clean.
• Pressure test the wellbore and PBP as required by regulatory requirements.
• Surface the tubing string, sandline bail a cement cap, and top fill with fresh water.

*Volumes and rates may need to be adjusted based on site-specific observations.