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Cementing Services
Manage Back Pressure in Cementing Job on Unconventional Horizontal Well

BACKGROUND

Onshore horizontal well of 5,530m TD with cement interval (0-5530m) at Sichuan Shale Gas. Due to narrow window between ECD and fracture pressure, significant mud loss encountered and background gas presented during the whole production section drilling.

CHALLENGES

  • Long cementing interval with high differential temperature: 300m/97degF and 5,530m/192degF
  • High slurry density@18.3ppg
  • Narrow density window between ECD and fracture pressure
  • Significant mud losses
  • Significant background gas
  • Lost centralizers & stop collars
  • Aging of chemicals: stored mixed fluid on rig over 24 days due to downhole complexity.

SOLUTIONS

  • Multi-FIT Cement System with EO10 elastoplastic additive.
  • Annulus clean up procedure for enhancing borehole clean up and coping with potential losses.
  • Retest the cement slurry after extensive delay and cement properties meet requirement before operation.
  • Manage back pressure on annulus during whole cementing operation.
  • Shut in annulus immediately upon bumping plug.
  • Oil-removal Spacer was utilized to enhance cement bond between formation and casing.

RESULTS

Cementing job was successfully accomplished with no losses and plug bumped as designed.