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In Oman’s mature Saih Raw field, an operator had historically experienced sloughing shale, downhole losses, and incidents of differential sticking. Due to the low formation pressures found in fields such as this one, there is often only a narrow operating margin between the pore pressure and formation breakdown. The low pressure does not allow for increased drilling fluid density, therefore causing a dilemma over how to address the borehole stability requirements without inducing fractures.

Saih Rawl deviated production wells typically consist of surface and intermediate sections, with kick-off points around 4040 m (13,255 ft), casing set around 4700 m (15,420 ft), and then drilled out at 80º through the four Barik formations. These formations are largely sandstone and shale layers and are depleted with formation pressures as low as 3,481 psi (4.1 ppg).

This section consequently experiences overbalanced pressures higher than 5,000 psi, which can cause differential sticking while high hydrostatic pressures are maintained to stabilize the transitional shales frequently leading to nonproductive time (NPT).

After two previous unsuccessful attempts at drilling this field, the operator approached Baker Hughes, a GE company (BHGE), for an alternative solution.

Analyzing data from offset wells in previous operations using the BHGE BRIDGEWISE™ engineering software, the BHGE team worked with the operator to develop a MAX-BRIDGE™ solution for this depleted well based around the NANOSHIELD™ sealant for extreme wellbore stability and BRIDGEFORM™ wellbore strengthening technologies.

Download the PDF to read the full case study.

Challenges & Results
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Challenges

  • Changing pressure in highly depleted formations in 563 m- (1,847 ft-) section
  • Achieving a buildup of 0º to 80º in reactive shale and depleted zones
  • Extremely overbalanced conditions
  • Sloughing shale
  • Deviated wellbore

Results

  • Successfully drilled the well to TD of 4570 m (14,990 ft) despite differentially pressured zones causing two offset failures
  • Eliminated NPT by minimizing downhole losses and incidents of differential sticking