Abstract

This paper describes the approach of an integrated team of Subsurface and Well Engineers to mitigate the substantial technical risks of a 3-well field development in offshore Sarawak, Malaysia. These challenges ranged from significant geohazard risks in the overburden to uncertainties regarding the extent of potential overpressure in the reservoir section.

The overpressure prediction in the reservoir section arose from detailed analysis of previous exploration and appraisal well abandonments, which indicated the potential for cross-flow from highly pressured sands in the under-burden.

To de-risk the execution phase of this campaign, a multi-disciplinary team of subsurface and well engineers focused on the following key factors:

  • Evidence for drilling hazards in offset wells

  • Evidence for cross-flow from deeper high pressured sands into the reservoir section

  • Geohazards identification in the overburden section

  • Data acquisition & real time monitoring

  • Pore pressure prediction

  • Mud-weight management

  • Integrated casing design

  • Hard-stop TD criteria for each well section

  • A range of "What-if Scenarios" that covered risk identification & mitigation

The well designs eventually selected for this development included both low angle (~40 deg inclination) and extended reach wells (~70 deg inclination) drilled to a target depth of some 21,000 ft.

The successful outcome of this challenging campaign can be attributed to good team integration, rigorous assessment of the risks based on all the available data, and excellent communication and co-operation between the office and rig during operations.

The team created "Well Trouble Plots" for every development well which summarizes the information regarding events such as losses, geohazards and mud weight from the offset wells.

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