SACK BLACK Enhances High Performance WBM, Eliminates Casing | Schlumberger
Case Study
Location
United States, North America, Onshore
Details

Challenge: Operator wanted to drill the wells and run 7 in. long string casing, which would eliminate an intermediate interval and, thus significantly reduce time and cost. 

Solution: KLA-SHIELD water base mud designed to provide wellbore stabilization by sealing microfractures in shale/coal formations and inhibiting the swelling and dispersion of sensitive shale and drill cutting exposed to water-based drilling fluids was used. 

Results: The well was drilled with no losses, stuck pipe or wellbore stability problems. Total time from spud to landing the 7 in. long string casing, including four days of open hole logging, was 18 days with no lost time due to mud problems.

Products Used

SACK BLACK Enhances High Performance WBM, Eliminates Casing

Well Information
 
Location Alaska
Spud May 21 – June 20, 2008
Intervals drilled 12 ¼ in from 70 ft to 3,041 ft (21 – 927 m)
  8 ¾ in from 3,041 ft to 7,005 ft (927 – 2,135 m) S-shaped well
Total well depth 7,005/6,780 ft TVD (2,135/2,067 m)
Disposal method Injection
Bottom hole temperature 110° F (43° C) Mud type/Density
  water-based 9.8 lb/gal (1.1 s.g.)
Completion type Gravel pack
Casing size 12 ¼ in 9 ⅝ in csg; 8 ¾ in Long string casing 7 in

The Situation

The operator wanted to drill the wells and run 7 in long string casing, which would eliminate an intermediate interval and, thus significantly reduce time and cost. The objective was to drill and run the long string through depleted production sands to the normally pressured target zone. The job posed inherent risks of stuck pipe, losses, as well as wellbore stability and well control Adding to the challenge were highly reactive clay/shale, coal beds and clay rich sands in the producing zones. Owing to environmental concerns and logistical challenges, mineral oil-based and synthetic-based drilling fluids were not an option.

The Solution

The M-I SWACO Houston lab performed characterization and analysis of formation samples with Mineralogy, CEC, Thin Section Analysis and Fracture Development tests. The test results lead M-I SWACO to recommend the operator use the KLA-SHIELD water base mud designed to provide wellbore stabilization by sealing microfractures in shale/coal formations and inhibiting the swelling and dispersion of sensitive shale and drill cutting exposed to water-based drilling fluids. Further, the results test data analysis indicated a 50/50 blend (6 lb/bbl each) of SACK BLACK and sulfonated asphalt should be incorporated for HTHP filtrate control and shale/coal stabilization. Continuous maintenance of 6 lb/bbl of SACK BLACK and proper particle size distribution of bridging material were recommended to prevent differential sticking threats in the depleted zones.

Key products used in the final KLA-SHIELD System comprised KLA-STOP, SACK BLACK, SAFECARB bridging agent (Using OPTIBRIDGE for PSD), Pac and sulfonated asphalt. LO-TORQUE and LUBE 776 were used as needed to reduce  torque and drag.

The Results

  • The well was drilled with no losses, stuck pipe or wellbore stability problems. Total time from spud to landing the 7 in long string  casing, including four days of open hole logging, was 18 days with no lost time due to mud problems
  • The KLA-SHIELD system provided excellent inhibition of reactive shale and clay, producing crisp angular cuttings
  • The mechanically sensitive shale remained stable
  • Drilled thru depleted zones with formation pressures of 3.5 ppg EMW to TD with pressures of ~9.8 ppg EMW and ECD’s of ~10 ppg EMW with no losses

 

SACK BLACK enhances high performance WBM, eliminates casing (Alaska)

The Details

This S shaped well was drilled in two intervals, 12 ¼ in surface and 8 ¾ in production. Of particular concern was drilling the production interval and running 7 in long string casing through the unconsolidated, depleted formation just below the casing shoe, to the normally pressured target formation.

A three-to-four day open hole logging run only magnified the concern of maintaining adequate wellbore integrity to allow the 7 in long string to be landed. Other concerns that were successfully avoided included lost circulation, stuck pipe and well control problems.

The performance of SACK BLACK was a major contributor to the success we had with KLA-SHIELD in these wells.”

Jim Cucullu, Project Engineer – M-I SWACO

Products Used

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