Schlumberger

Case Study: Steering Optimization Increases Oil Recovery in Mature South China Sea Field

RSS and LWD service enable Xijiang Operating Company to place horizontal sidetrack in narrow window of reservoir

Challenge: Land and place sidetrack horizontal section within narrow window to avoid oil/water contact (OWC) and prolong well’s producing life.

Solution: Steer sidetrack with PowerDrive Xceed RSS for harsh, rugged environments guided by real-time images from EcoScope multifunction LWD service.

Result:

  • Kept sidetrack above oil/water contact.
  • Achieved 100% net to gross.
  • Increased oil production.
  • Reduced water cut.

Recover remaining oil

Xijiang Operating Company, the operator of a mature oil field in block XJ24-3 in the Pearl River Mouth basin of the South China Sea, was planning to drill sidetrack horizontal wells to recover the remaining oil in the Hanjiang formation. One of these wells—XJ24-3-ST—targeted a three-layer reservoir in which sands with high porosity and permeability were interbedded with shales.

The well was to be placed in the reservoir’s second layer, immediately below the interbedded shale in the upper part of the reservoir. Because it was expected that oil production had raised the OWC level in the reservoir, the sidetrack needed to be kept within 1 m of the bottom of the shale to prolong the well’s producing life.

Place sidetrack within narrow window

Xijiang’s well placement objective was achieved through teamwork, collaboration, and the use of a PowerDrive Xceed RSS for harsh, rugged environments and the EcoScope multifunction LWD service. Real-time density images from the EcoScope service guided well placement decisions, and the PowerDrive Xceed RSS ensured quick response for any trajectory adjustments needed.

The sidetrack was landed smoothly 0.5 m below the shale with no gooseneck—despite the target being deeper than the original plan indicated. Then the horizontal section was kept 0.5 m below the shale, in the middle of the 1-m target window, until 30 m from TD. At that point, the well was intentionally drilled upward into the shale to acquire a structural depth control point for future field development purposes.

Increase production and reduce water cut

Net to gross in the 323-m horizontal section of the XJ24-3-ST sidetrack was 100% and the productivity index was excellent. During a subsequent performance test, oil production stabilized at 2,000 bbl/d—500 bbl/d more than the expected rate. Water cut was 31%, substantially less than the field average.

This success was achieved by combining the capabilities of the PowerDrive Xceed RSS and EcoScope service with the knowledge and dedication of the well placement team, which included geologists and geophysicists, well placement and LWD engineers, and directional drillers. Team members on site were able to interact, collaborate, and communicate in real time with team members onshore.


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