Case Study: TDDirect CD Service Saves Apache Energy 7 Rig Days in Australia’s North West Shelf

Casing while drilling finishes 12 1/4-in, 1,054-m horizontal well section in one run

Challenge: Drill a 12 1/4-in horizontal well section of at least 1,000 m in an unstable formation offshore Australia.

Solution: Use a TDDirect CD casing-while-drilling service with a rotary steerable system (RSS) assembly and an underreamer.

Result: Cased while drilling a 1,054-m horizontal well section in one run, saving 7 rig days.

Demanding application causes excessive NPT

While working in Australia’s North West Shelf, Apache Energy encountered wellbore instability while drilling development wells, which caused hole problems and the loss of a wellbore. During the operation, greater-than-normal NPT resulted from controlling circulation losses, making wiper trips, tripping in and out, and running casing. Apache wanted to reduce NPT-related costs and improve performance by reducing off-bottom risks when drilling the 12 1/4-in sections.

Greater wellbore integrity eliminates borehole collapse issues

To help Apache reduce NPT and minimize operational risk, the TDDirect CD casing-while-drilling service with a retrievable BHA was used. The 12 1/4-in section was directionally drilled from the 13 3/8-in shoe to TD in a single run, using 9 5/8-in casing instead of a conventional drillstring. Casing the wellbore while drilling eliminated the danger of borehole collapse before casing could be run.

The TDDirect CD service retrievable BHA included an RSS to drill a pilot hole and an underreamer to enlarge the borehole to 12 1/4 in. The BHA was actively steered to avoid unstable regions and wellbore collision risks using real-time MWD measurements. The resulting wellbore inclination increased from 27° to 90°, holding angle to section TD at 2,197-m MD and 723-m TVD. Once TD was reached, the underreamer's cutters were retracted, the BHA was unlocked from the 9 5/8-in casing and retrieved on drillpipe, and the casing was cemented.

Casing while drilling saves 7 rig days, sets world records 

Compared with nearly 13 days to drill the offset well by conventional means, the TDDirect CD service ran casing to TD while drilling in 5.88 days, saving approximately 7 rig days. In addition to reducing Apache's NPT-related costs and drilling time, the run eliminated the need for a long liner run on the next section. The operation also resulted in three TDDirect CD service world records for

  • the longest 9 5/8-in interval drilled in one run with a single retrievable casing-while-drilling BHA
  • the longest 9 5/8-in horizontal section drilled—1,054 m with a TVD of 723 m
  • the longest 9 5/8-in horizontal well section drilled with a casing-while-drilling RSS BHA—3.04 throw ratio of MD to TVD.

Download: TDDirect CD Service Saves Apache Energy 7 Rig Days in Australia’s North West Shelf (0.51 MB PDF)

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