Schlumberger

Case Study: Precise Well Placement for Horizontal Campaign Increases Oil Production 30% in Bohai Bay

Advanced suite of LWD services guides geosteering of nine horizontal wells, RSS boosts drilling efficiency 60% to save USD 3.2 million off AFE for CNOOC

Challenge: Drill nine horizontal wells to develop a marginal oil field with stratigraphic and structural uncertainties and unknown gas/oil contact (GOC) and oil/water contact (OWC) levels.

Solution: Geosteer lateral sections with EcoScope multifunction LWD service for fluid property evaluation and PeriScope bed boundary mapper to stay in zone with distance-toboundary measurements.

Result:

  • Successfully placed nine horizontal wells, including one injection well, achieving production rate 30% higher than comparable set targets.
  • Saved USD 3.2 million off AFE with 60% improvement in drilling efficiency.

Drill nine horizontal wells to develop marginal oil field 

Chinese National Offshore Oil Corporation (CNOOC) planned to develop a marginal oil field  in Bohai Bay, China, where a pilot study showed that the reservoirs are distributary channel sands of a shallow water deltaic depositional system. Seismic inversion indicated that the sand properties and connectivity vary dramatically across the field. A multiple-aquifer system was apparent, and the gas/oil contact (GOC) and oil/water contact (OWC) levels were unknown. Furthermore, the only well control was from three vertical exploration wells and two directional offset wells.

The plan was to drill nine horizontal wells, including one injector well, gain reservoir exposure throughout the small 9-km2, oil-bearing area of a marginal oil field. This target area was isolated by secondary faults and stratigraphic depositional borders.

Acquire real-time data to guide geosteering

Understanding the need to evaluate stratigraphic uncertainties and establish an accurate picture of the targeted reservoir, Schlumberger provided PeriScope bed boundary mapper and EcoScope multifunction LWD service to acquire real-time measurements to guide geosteering of the horizontal wells. EcoScope service was deployed to evaluate fluid properties and identify the GOC level. PeriScope service was used to clearly delineate the channel sand body boundaries along the horizontal sections. A rotary steerable system (RSS) was included in the BHA to maximize drilling efficiency and trajectory control.

Improve drilling efficiency 60%, saving USD 3.2 million
off AFE

All nine horizontal wells were precisely placed in optimal positions for injection and drainage with a 100% success rate, using real-time measurements from PeriScope mapper and EcoScope service to guide geosteering. With accurate data guiding decisions and a powerful RSS for drilling, the team increased ROP and avoided unplanned exits for a 60% improvement in drilling efficiency. This improvement equated to savings of USD 3.2 million off AFE for CNOOC.

Drilling Efficiency Production Performance
Producer
Well
Horizontal Length (m) Drilling Time (h)
Saved Time (h)
Actual Production Water Cut (%)
1
800
48, 7
85
1.2
2
304
17, 36.5
86
23.9
3
305
14.5, 39.5
116
0.3
4
385
28.7, 25.3
66
2.0
5
490
13.3, 40.7
125
19.3
6
667
26, 28
200
0.4
7
346
7.5, 46.5
212
2.1
8
447
22, 32
171
15.4
Injector well
560
20, 34
   

Production from these horizontal wells surpasses the set production target by 30%, with extremely low water cut. The integrated LWD, well placement, and RSS solution optimized the marginal oil field into a much more economic development oil field.


Download: Precise Well Placement for Horizontal Campaign Increases Oil Production 30% in Bohai Bay (0.32 MB PDF)

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LWD Services Place Nine Horizontal Wells Within Targeted Channel Sands

Log shows the PeriScope mapper clearly delineated the channel sand body boundaries along the horizontal section.
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"The advantages from EcoScope service and PeriScope mapper enabled the team to make effective real-time decisions for placing the trajectory in the best place to drain the remaining hydrocarbon."
Chao Mien Nie
Chief G&G
CNOOC Tianjin, Bohai Bay

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