CHALLENGE Drill an S-shaped well at high ROP, identify gas/oil contact (GOC), and land the well below GOC in a highly deviated section without the use of a chemical nuclear source for logging. SOLUTION Use NeoScope* sourceless formation- evaluation-while-drilling service for identification of GOC without a chemical source and Orion II* telemetry platform for faster data transmission. RESULTS Maintained high ROP, identified GOC in the target sandstone at 5,454 ft MD in real time, and obtained high-quality spectroscopy data for quantitative lithology to set the 7-in liner without a chemical nuclear source. “We are pleased with the NeoScope service and the correlation of the sourceless neutron-gamma density with density logs from nearby wells. After this success, we would recommend use of this service on future wells where handling of chemical sources is a concern.” —Pearl Oil, Thailand Maintain high ROP, obtain quality logging data offshore Thailand Pearl Oil operates in the Gulf of Thailand where fast drilling at rates of more than 1,000 ft/h is the standard. The company was drilling an S-shaped well at high ROP and needed to identify GOC to land the well approximately 5 ft below GOC in a highly deviated section. However, obtaining logging data with a chemical nuclear source was risky in this complex formation with poor borehole conditions. To obtain the full suite of real-time measurements that Pearl needed, Schlumberger introduced the NeoScope sourceless formation evaluation service. CASE STUDY Drilling NeoScope Sourceless LWD Data Identifies GOC at High ROP to Land Offshore Well for Pearl Oil Real-time logging without a chemical nuclear source provides high-quality data in highly deviated section Sourceless NeoScope integrated analysis includes net pay flag. Sourceless neutron porosity, sourceless neutron-gamma density, and sigma crossover are used to identify GOC. , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , GOC Sigma-neutron Sourceless NGD density ROP Averaged Over Last 5 ft, Recorded Mode 2,000 ft/h MD ft TVD ft 0 90 Hole Deviation 0 ° 13 Ultrasonic Caliper Average 8 in 13 Bit Size 8 in 50 Sigma Formation, Average Gas Indication 0 cu 0 Best Thermal Neutron Porosity, Average 0.5 ft 3 /ft 3 2.95 Bulk Density from Neutron, Average Gas Indication 1.95 g/cm 3 -0.15 Best Thermal Neutron Porosity, Average 0.45 ft 3 /ft 3 2,000 Phase Shift Resistivity 16-in Spacing at 2 MHz, Environmentally Corrected 0.2 ohm.m 2,000 Phase Shift Resistivity 22-in Spacing at 2 MHz, Environmentally Corrected 0.2 ohm.m 2,000 Phase Shift Resistivity 28-in Spacing at 2 MHz, Environmentally Corrected 0.2 ohm.m 2,000 Phase Shift Resistivity 34-in Spacing at 2 MHz, Environmentally Corrected 0.2 ohm.m 2,000 Phase Shift Resistivity 40-in Spacing at 2 MHz, Environmentally Corrected 0.2 ohm.m Gamma Ray, Average 0 gAPI 200
Transcript
CHALLENGEDrill an S-shaped well at high ROP, identify gas/oil contact (GOC), and land the well below GOC in a highly deviated section without the use of a chemical nuclear source for logging.
SOLUTIONUse NeoScope* sourceless formation- evaluation-while-drilling service for identification of GOC without a chemical source and Orion II* telemetry platform for faster data transmission.
RESULTSMaintained high ROP, identified GOC in the target sandstone at 5,454 ft MD in real time, and obtained high-quality spectroscopy data for quantitative lithology to set the 7-in liner without a chemical nuclear source.
“We are pleased with the NeoScope service and the correlation of the sourceless neutron-gamma density with density logs from nearby wells. After this success, we would recommend use of this service on future wells where handling of chemical sources is a concern.”
—Pearl Oil, Thailand
Maintain high ROP, obtain quality logging data offshore ThailandPearl Oil operates in the Gulf of Thailand where fast drilling at rates of more than 1,000 ft/h is the standard. The company was drilling an S-shaped well at high ROP and needed to identify GOC to land the well approximately 5 ft below GOC in a highly deviated section. However, obtaining logging data with a chemical nuclear source was risky in this complex formation with poor borehole conditions. To obtain the full suite of real-time measurements that Pearl needed, Schlumberger introduced the NeoScope sourceless formation evaluation service.
CASE STUDY
Drilling
NeoScope Sourceless LWD Data Identifies GOC at High ROP to Land Offshore Well for Pearl OilReal-time logging without a chemical nuclear source provides high-quality data in highly deviated section
Sourceless NeoScope integrated analysis includes net pay flag. Sourceless neutron porosity, sourceless neutron-gamma density, and sigma crossover are used to identify GOC.
Sourceless density
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Sigma-neutron
Sourceless NG
D density
ROP Averaged Over Last 5 ft,
Recorded Mode
2,000 ft/h
MD ft
TVDft0
90
Hole Deviation
0 °
13
Ultrasonic Caliper Average
8 in
13
Bit Size
8 in
50
Sigma Formation, Average
Gas Indication
0 cu
0
Best Thermal Neutron Porosity, Average
0.5 ft3/ft3
2.95
Bulk Density from Neutron, Average
Gas Indication
1.95 g/cm3
-0.15
Best Thermal Neutron Porosity, Average
0.45 ft3/ft3
2,000
Phase Shift Resistivity 16-in Spacing at 2 MHz, Environmentally Corrected
0.2 ohm.m
2,000
Phase Shift Resistivity 22-in Spacing at 2 MHz, Environmentally Corrected
0.2 ohm.m
2,000
Phase Shift Resistivity 28-in Spacing at 2 MHz, Environmentally Corrected
0.2 ohm.m
2,000
Phase Shift Resistivity 34-in Spacing at 2 MHz, Environmentally Corrected
0.2 ohm.m
2,000
Phase Shift Resistivity 40-in Spacing at 2 MHz, Environmentally Corrected
0.2 ohm.m
Gamma Ray, Average
0 gAPI 200
CASE STUDY: Pearl Oil avoids risk of using chemical source in complex formation while logging at high ROP
Obtain petrophysical data with sourceless LWD technologyThe NeoScope service—the industry’s only pulsed-neutron-generator-based (PNG) LWD technology—reduces risk by eliminating the need for chemical sources. The service also provides the complete petrophysical data needed in the shortest multifunction LWD collar available. The Orion II telemetry platform increases the flow of real-time data LWD and MWD systems to enhance decision making.
Using NeoScope service, the sourceless neutron-gamma-density (SNGD) measurement was obtained by detecting the gamma rays emitted from the formation nuclei through their interactions with neutrons generated by PNG. PNG nuclear logging data was obtained without the risks associated with traditional chemical nuclear logging sources, and spectroscopy and sigma were acquired for formation lithology and salinity.
Set liner with more data and less riskNeoScope service provided Pearl with the data it needed while reducing the risk associated with a chemical nuclear source. More than 15 measurements were sent to surface at more than 1,000 ft/h through the Orion II downhole telemetry platform to identify GOC. The Orion II platform quickly provided the real-time data critical to determining where to set the 7-in liner in the highly deviated section.
The logging interval was from 1,200 to 5,480 ft MD, and GOC in the target sandstone was identified at approximately 5,454 ft MD. The recorded-mode data, including SNGD and spectroscopy measurements, were used for further petrophysical analysis.
Crossplot between neutron porosity and SNGD (left) and between SNGD-corrected matrix porosity and sigma (right).
Gas-bearing sands
Sandstone
Limestone
Dolomite
FZone 1 Reservoir gas
Gas-bearing sands
2.0 50
35
20
5
2.3
2.6
2.9
-15 0 15 30 45 0 10 20 30 40 50
Sigma = 36.362 cu
Best thermal neutron porosity, average (matrix limestone), %
Density porosity of matrix, %
Sour
cele
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mm
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rage
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Gas-bearing sands
Sandstone
Limestone
Dolomite
FZone 1 Reservoir gas
Gas-bearing sands
2.0 50
35
20
5
2.3
2.6
2.9
-15 0 15 30 45 0 10 20 30 40 50
Sigma = 36.362 cu
Best thermal neutron porosity, average (matrix limestone), %
Density porosity of matrix, %
Sour
cele
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CASE STUDY: Pearl Oil avoids risk of using chemical source in complex formation while logging at high ROP
Sourceless NeoScope logs (left) and petrophysics integrated analysis (right).
MD ft
4,600
4,700
4,800
4,900
5,000
5,100
5,200
5,300
5,400
GOC
G S R PD L
NetReservoir
NetPay
F R Salt
Coal
Siderite
Anhydrite
Pyrite
Dolomite
Calcite
Quartz-Feldspar-Mica
Clay
Ultrasonic Caliper Average
in8 13
Bit Size
in8 13
Gamma Ray, Average
Gamma Ray, Caliper, ROP
gAPI0 200
ROP Averaged Over Last 5 ft, Recorded Mode
ft/h2,000 0
Sigma Formation, Average
cu0 50
Neutron and Density
Best Thermal Neutron Porosity, Average
ft3/ft30.5 0
ft3/ft3 0.5-0.15
Blended Attenuation Resistivity 40 in
ohm.m0.1 200
Blended Attenuation Resistivity 34 in
ohm.m0.1 200
Blended Attenuation Resistivity 28 in
ohm.m0.1 200
Blended Attenuation Resistivity 22 in
ohm.m0.1 200
Blended Attenuation Resistivity 16 in
Blended Attenuation Resistivity
ohm.m0.1 200
Thermal Neutron Porosity (Ratio Method) in Selected Lithology
ft3/ft30.45
0.45
-0.15
Best Thermal Neutron Porosity, Average
g/cm31.95 2.95
Neutron-Gamma-Density, Average
ft3/ft3 0
Matrix Adjusted Density Porosity
0.5 ft3/ft3 0
Matrix Adjusted Neutron Porosity
Gas Effect
Gas Effect
Gas Effect
<--Sand shale
<--RZone_1
www.slb.com/NeoScope*Mark of Schlumberger
Note: Japan Oil, Gas and Metals National Corporation (JOGMEC), formerly Japan National Oil Corporation (JNOC), and Schlumberger collaborated on a research project to develop LWD technology that reduces the need for traditional chemical sources. Designed around the pulsed neutron generator (PNG), NeoScope service uses technology that resulted from this collaboration. The PNG and the comprehensive suite of measurements in a single collar are key components of the NeoScope service that deliver game-changing LWD technology.
