Schlumberger

Case Study: Shallow Horizontal Well Landed at 197.55 Meters TVD in Romania

Lessons learned in previous drilling and PowerPak XP steerable motor help OMV Petrom place well as planned in Suplac field heavy-oil reservoir

Challenge: Place horizontal well at less than 200 m TVD in unconsolidated sands of shallow heavy-oil reservoir without entering limestone, while contending with rig equipment limitations.

Solution: Use BHA incorporating PowerPak XP extended power steerable motor, Smith Bits Xplorer Expanded XR+VC soft formation milled tooth drill bit, and SlimPulse retrievable MWD service.

Result:

  • Successfully landed well at 197.55 m TVD and drilled 300-m horizontal drain without entering limestone.
  • Kept maximum dogleg severity within planned limits.
  • Achieved planned ROP.
  • Saved two cleanup trips.
  • Realized planned time-depth curve and costs.

Place well close to surface

Placement of Suplac H3W—a well OMV Petrom was drilling in Suplac field in northwestern Romania—was a challenge because the target heavy-oil reservoir was very close to the surface. The well plan called for landing the 12 1/4-in section at just 199 m TVD, then drilling an 8 1/2-in drain horizontally through the reservoir’s unconsolidated sands without entering the limestone. Equipment limitations added to the challenge. The rig on the Suplac H structure had a single-stand derrick, which precluded the use of a surveying tool during the kickoff from vertical—it had to be done with just a bit and motor on drillpipe, using a natural landmark as reference for the well azimuth.

Keep dogleg severity within planned limits

Working together, OMV Petrom and Schlumberger successfully met the well placement challenge. The 12 1/4-in hole section was landed at 197.55 m TVD with an inclination of 88.5°, using a BHA that included an Xplorer Expanded XR+VC drill bit, a PowerPak XP motor with 4:5 lobes and the bent housing set at 2.12°, and a SlimPulse retrievable MWD service for surveying and gamma-ray logging. Maximum dogleg severity in the section was 14.70°/100 ft—within the planned limits.

For drilling the 8 1/2-in horizontal drain section, the steerable motor’s bent housing was set at 1.15°. Losses were anticipated because they had been experienced while drilling the drain section of the previous well in the campaign, so loss-control measures were implemented. The risk of uncertainty in the location of geological features of interest was mitigated by carefully monitoring parameters while drilling and mapping the bit by cuttings analysis. TD was called at 621 m MD, giving a drain length of 300 m.

Set record for shallow well drilled by Schlumberger

The TVD of 197.55 m achieved with the PowerPak XP BHA made Suplac H3W the shallowest well Schlumberger had ever recorded, surpassing the previous record of 237 m TVD (199 m TVD subsea). Lessons learned on the first well of OMV Petrom’s horizontal drilling campaign in Suplac field helped the team avoid entering the limestone. Additional time savings were realized by avoiding hole cleanup trips. The well was drilled at the planned ROP, and the planned time-depth curve and well costs were matched.


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