Download - Day 2 - 1 FormEval-Intro
Formation Evaluation
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Formation Evaluation
ObjectivesFormation Evaluation
• Describe the information that can be obtained from a mud log and from three types of core samples.
• List six conventional openhole well logs and describe the information that can be obtained from each.
• List six conventional cased hole well logs and describe the information that can be obtained from each.
• Calculate water saturation using Archie’s equation, given well log readings.
Formation Evaluation
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OutlineFormation Evaluation
• Mudlogging• Cores • Logging while drilling (LWD)• Openhole Wireline logs• Cased-Hole Wireline logs
Introduction
Formation Evaluation
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The Life of a Reservoir
Gather All Data
Operating Company
Logs BoreholeSeismic
2D/3DSurfaceSeismic
RegionalDataGeological
Data
CoreData
Informationfrom nearby
wells
Formation Evaluation
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Subsurface Petrophysical Procedures
Mudlog Example
Visu
al P
oros
ity
Drilling RateM. per Hr.
20 15 10 5
Dep
th (m
)
CuttingsLithology
Continuous TotalGas in air %
1 10 PPM 1 K 10 K
Hydrocarbon AnalysisChromotograph PPM
AnalysisMethane--- Ethane---Propane--- Butane---
Pentane---
Remarks
Inte
rpre
ted
Lith
olog
y
LS: wht, dk, br, vf, xin, cin, hdw tr foss
SH: dk gy, gy, frm, occ sft,occ sity
SS: lt gy, cir, xin, sb ang, sb, rnd, m grn, oil stn, bri yelflour, bri gid stng cut
SH: dk gy, gy, frm, occ sft,occ sity
SS: lt gy, cir, xin, sb ang, sb,rnd, m grn, oil stn, bri yelflour, bri gid stng cut
SH: dk gy, gy, frm, occ sft,occ sity
Formation Evaluation
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Cores• Allow direct measurement of reservoir
properties
• Used to correlate indirect measurements, such as wireline/LWD logs
• Used to test compatibility of injection fluids
• Used to predict borehole stability
• Used to estimate probability of formation failure and sand production
Information from Cores
• Porosity• Horizontal
permeability to air• Grain density
• Vertical permeability to air
• Relative permeability• Capillary pressure• Cementation exponent
(m) and saturation exponent (n)
Standard Analysis Special Core Analysis
Formation Evaluation
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PDC Cutters
Fluidvent
Drill collarconnection
Inner barrel
Outer barrel
Thrust bearing
Core retainingring
Core bit
Coring Assembly and Core Bit
(Whole Core Photograph, MisoaSandstone, Venezuela)
Whole Core
Formation Evaluation
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Sidewall Sampling Gun
Core bullets
Core sample
Formation rock
Sidewall Coring Tool
Coring bit
Samples
Formation Evaluation
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Well Log Analysis
• Openhole logs• Cased-hole logs
Well LogSP Resistivity
Openhole Log Evaluation
Formation Evaluation
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Gammaray
Resisitivity Porosity
Increasingradioactivity
Increasingresistivity
Increasingporosity
Shale
Oil sand
Shale
Openhole Well Logs• Passive measurements
• Gamma ray: Indicates lithology• Spontaneous potential: Indicates
lithology• Caliper: Hole condition
• Active measurements• Resistivity: Fluid saturation, fluid type• Porosity: Rock properties, quantity of
hydrocarbon• Density: Rock properties, seismic
response• Sonic log: Rock properties, seismic
response
Cap rock
Reservoir rock Source rock
Oil
Formation Evaluation
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Well Log InterpretationLogs provide detailed essential information on wells and reservoirs
Well
Depth
• Rock type• Porosity• Permeability• Fluid type• Fluid volume• Formation tops• Fractures
Granite
Sandstone
Limestone
Shale
Claystone
Common Types of Logs
• Gamma (GR)• Spontaneous Potential (SP)• Sonic (DT)• Density (RHOB)• Neutron (CNT)• Resistivity (LLD)
Formation Evaluation
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MotorSurface-adjustable
bent housing
Inclination RPMgravity toolface
Stabilizer and bearings
Measurementantenna
Azimuthal resistivity(depth of investigation
12 in. or less)Gamma ray
detector
3/4º fixed bent housing
Transmitter forwireless telemetryand measurement
of current
Logging While Drilling
Logging While Drilling (LWD)
• Provides:– Real time correlation for picking coring
and casing points– Real time overpressure detection in
exploration wells– Real time logging to minimize “out of
target” sections (geosteering)– Real time formation evaluation to
facilitate “stop drilling” decisions
Formation Evaluation
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Cased-Hole Logs
Formation Properties From Cased-Hole Logs
• Porosity
• Saturation
• Permeability
• Reservoir geometry
• Temperature and pressure
Formation Evaluation
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Why Log Cased Wells?
• To monitor production:– Fluid contact detection and movement – Other water/gas movement– Injection front advance– Water salinity
Common Cased-Hole Logs
• Gamma ray log• Natural gamma ray spectrometry log• Neutron log• Sonic log• Thermal decay time log• Gamma ray spectrometry log