Proactive Geosteering in Kuwait’s Burgan Siliciclastic Reservoir (World’s Second Largest Reservoir)

Kuwait, a country situated in the Eastern Arabia at the tip of Persian Gulf, constitutes one of the world’s largest siliciclastic oil reservoir (Greater Burgan Field) on the earth, according to the American Association of Petroleum Geologists (AAPG).

The formation comprised of sand, silt and shale layers. The upper Burgan target zone was characterized as fluvial channel deposit with clean gamma and high resistivity sandstone.

Geosteering Objective:

The geosteering objective was to optimize the horizontal wellbore position within upper Burgan clean sandstone interval.

Challenges:

• Uncertainty in seismic data.
• Lateral variations within target zone.
• Target zone thickness variation along borehole section.

Tools Utilized:

• Halliburton’s Azimuthal Deep Resistivity (ADR)
• Density image
• Triple combo

Geosteering Summary:

The wellbore was landed within the target zone having distinctive clean gamma and high resistivity features of the zone. The upper and lower reservoir boundaries were shale layers with good resistivity contrast of 1:100. The ADR resistivity inversion was utilized for reservoir boundary mapping. The geosignals provided initial confirmation of reservoir boundary approaching. The resistivity image was plotted in real-time to make quick decisions. The density image was giving a close estimate of formation dips in real-time. The wellbore was placed very well within the reservoir target zone utilizing ADR’s distance-to-bed inversion and geosignals in combination with density and resistivity image data. The density and porosity data confirmed the wellbore position within the target zone.

Overall the objectives of proactive geosteering were largely achieved with good success in mapping reservoir boundary. The actual reservoir surface was 30-40 feet shallower than original surface along borehole section.

Conclusion:

• Knowledgeable personnel (Geosteering specialists)
• Extensive knowledge of deep azimuthal resistivity (ADR) tool’s responses.
• Utilizing the resistivity inversion algorithms added the value in determining reservoir boundaries with higher confidence.
• Without proactive geosteering, the well wouldn’t have achieved desired results and lateral wellbore objectives.