Schlumberger

Performance Report: MEGADRIL Meeting All Objectives in 175-Well Offshore Drilling Campaign

Challenge: The operator programmed an extended reach well that posed a number of technical demands, including an extremely long 27,274 ft ( 8,301 m) 9 ⅝-in. liner in the 12 ¼-in. hole. In addition, the well was designed with more than 6.3 miles (10.14 km) of lateral offset, which was restricted by extremely limited deck space and pit capacity on the rig.

Solution: M-I SWACO recommended the MEGADRIL oil-base drilling fluid system with MEGAMUL, a single-drum emulsifier/wetting agent package that simplifies maintenance, logistics, and reduces inventory on location. MEGADRIL is engineered to provide a stable emulsion, inherent low HTHP filtrate and lower rheological properties than a traditional invert‐emulsion system, which combines to lower pump pressure and ECDs. Consequently, MEGADRIL is the preferred system when tight emulsions and thinner fluids are required. The system already had been proven to be effective over a wide range of temperatures, densities and oil-water ratios in over two hundred vertical and deviated wells.

Result:

  • Successfully drilled the longest extended well in North America
  • World’s longest extended-reach well drilled from an offshore fixed platform drilling rig
  • Extremely fast drilling process and high quality wellbore saved 90 days drilling time
  • Reduced well AFE by 20%
  • Zero environmental incidents

The 17 ½ in. sections, with an average section length of 876 m (2,874 ft), were drilled with densities ranging between 9.2 to 11.0 lb/gal (1.1- 1.3 s.g.). Inclinations ranged from vertical to 71º.

The 12 ¼ in. sections averaged 987 m (3,238 ft) in length and were drilled with mud weights of 8.8 to 11.8 lb/gal (1.0-1.4 s.g.). The maximum hole section was 74 degrees, and it represented the longest section drilled so far.

The 8 ½ in. sections were drilled to an average length of 905 m (2,969 ft) with a density range of 7.0 to 11.5 lb/gal ( 0.84 -1.3 s.g.) and inclinations from 59º to 90º.

In one of the development wells, the pore pressure was below the water gradient. Consequently, the client wanted to drill an 8 ½ in. section horizontally with a mud density <7.3 lb/gal (0.87 s.g.). In the initial displacement, the MEGADRIL system was mixed with the following properties:

  • Density: 7.0 lb/gal (0.84 s.g.)
  • Viscosity: 49 sec
  • PV/YP: 14/10
  • R6/R3: 5/4
  • Gels: 4/6
  • HTHP at 300º F (149º C) 4.0 cc
  • OWR: 90:10
  • ES: 550 volts (un-sheared)
  • Excess Lime: 4.25
  • Chlorides 8,500 mg/l in brine phase

Although about 7,418 bbl was lost to the formation while drilling, this development well was drilled and cased successfully with the 7 in. liner. No previous attempts had been effective, which led the client to consider underbalanced drilling as a potential solution.

Owing to the limited space on the rig, M-I SWACO is only using six major chemicals to formulate the MEGADRIL system, including MEGAMUL, MEGATROL, VG PLUS, lime, CaCl2 as well as the EDC Diamond base oil.


Download: MEGADRIL Drills the Longest Extended-Reach Well in North America (0.46 MB PDF)

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