COMMERCIAL BOREHOLE LOGGING

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COMMERCIAL BOREHOLE LOGGING

• PAUL SPIELMAN
• September 2007

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From Warrior Energy Services Website,
www.warriorenergyservices.com
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TYPICAL WIRELINE TRUCK
From Welaco
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TYPICAL WIRELINE SKID UNIT
Welaco Unit at Ormats Puna Geothermal Venture in
Hawaii
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TYPES OF LOGS

• Geophysical Logs
• Resistivity
• Porosity
• Gamma Ray
• Dip Meter
• Borehole Imaging
• Other

• Production Logging
• Pressure
• Temperature
• Spinner
• Fluid Density
• Well Inspection
• Sonic
• Caliper
• Electro-magnetic
• Ultrasonic
• RA Tracer
• Video

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RESISTVITY LOGS

• Measure bulk resistivity of formation
• Laterlog
• The original well log
• Electrodes direct current into formation to
  ground electrodes on surface
• Induction
• Magnetic field induces current in formation
• Used with low conductivity well fluids
• Porosity can be calculated if water salinity is
  known
• Oil or gas saturation can be calculated if
  porosity and water salinity are known

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POROSITY LOGS

• Neutron tool
• Neutron source
• High energy neutrons are slowed down by hydrogen
  atoms in water (or oil) and detected by tool
• Porosity is function rock type and slow neutron
  count
• Density tool
• Gamma ray source
• Electrons reflect gamma rays back to detector in
  tool
• Electrons in formation proportional to density
• Porosity is function of rock type and density
• Sonic tool
• Measures speed of sound in formation
• Porosity slows sound
• Porosity is function of rock type and measured
  speed of sound

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GAMMA RAY LOG

• Gamma ray detector measures natural radioactivity
  of formation
• Mostly due to Potassium in Shale
• Shale has porosity but no permeability
• Uranium and Thorium
• Less common sources natural radioactivity
• Detected by more sophisticated tools that measure
  gamma ray energy
• Run with other tools to correlate logs

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DIP METER AND BOREHOLE IMAGING

• Dip Meter
• Four or six arms with few buttons measure small
  scale resistivity
• Wellbore inclination and orientation
• Map bedding planes of sedimentary formations
• Imaging Tools
• Resistivity imaging tools
• FMI - Schlumberger, EMI Halliburton
• Pads with many buttons map small scale
  resistivity
• Ultrasonic imaging tools
• USIT Schlumberger, CAST Halliburton
• Spinning ultrasonic transducer measures I.D. and
  sonic impedance
• Borehole image
• Dip and orientation of fractures
• Structure and stress of formation
• Borehole breakout
• Drilling induced fractures

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OTHER GEOPHYSICAL LOGS

• Mineral identification
• Pulsed neutron source stimulates gamma ray
  emissions
• Tool measures energy spectrum of returning gamma
  rays
• Percentage of elements (silica, calcium, etc.)
• Magnetic resonance
• Detects free water
• Determine permeability

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GEOTHERMAL APPLICATIONS

• Geophysical tools designed for sedimentary
  formations
• Algorithms for sandstone, shale, limestone,
  dolomite
• Special algorithms required for crystalline rock
• Resistivity tool is sufficient to quantify
  porosity when water salinity is known
• Sonic tool puts seismic surveys on depth
• Density tool calibrates gravity surveys
• Formation imaging tools map fractures and
  quantify stress regime
• Neutron and density tools can identify lithology,
  
• if samples are available to create correlations
• if there is variation in rock type

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Schlumberger Litho-Density Log
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COMPANIES

• The Big Three
• SCHLUMBERGER
• HALLIBURTON
• BAKER ATLAS
• Worldwide Geophysical, Production Inspection
  Logging
• Video
• DOWNHOLE VIDEO Oxnard CA
• many other companies

• Geothermal Production Logging
• WELACO Bakersfield CA
• PACIFIC PROCESS SYSTEMS Bakersfield CA
• SCIENTIFIC PRODUCTION SERVICES Houston TX
• INSTRUMENT SERVICES INC. Ventura CA
• Pressure-Temperature-Spinner
• some other services
• Sell and service equipment
• Many other companies in Japan, New Zealand,
  Philippines, Iceland, Kenya (KenGen), etc.

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PRODUCTION LOGS

• Very useful in geothermal wells
• Can be run with simple or sophisticated equipment
• Temperature surveys are essential for exploration
  work
• Pressure Temperature surveys are more useful
  for well testing and production

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TEMPERATURE LOGS

• Most important parameter in geothermal wells
• Thermocouple wire
• easiest for shallow holes
• RTD
• most accurate
• Mechanical tool
• Only option for deep hot wells 10 years ago
• Electronic surface readout tool in thermal flask
• Requires high temperature wireline
• Electronic memory tool in thermal flask
• State of the art
• Slick line or braided cable
• Fiber Optics
• Instantaneous temperature profile of entire
  wellbore
• Good for measuring transients
• High temperature electronics
• Not yet commercial

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TEMPERATURE PROFILE
SURFACE
CONDUCTIVE GRADIENT
DEPTH
HYDROTHERMAL SYSTEM
OUTFLOW ZONE
UPFLOW
TEMPERATURE REVERSAL
CONDUCTIVE HEAT SOURCE
TEMPERATURE
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PRESSURE LOG

• Second most important reservoir parameter
• pressure drives flow
• producing drawdown indicates reservoir
  productivity (or injection buildup)
• drawdown curves analyzed to determine reservoir
  permeability
• Water level, easily measured
• used in hydrology but less useful in geothermal
  systems
• dependant on wellbore temperature and gas or
  steam pressure above water
• Mechanical pressure tool
• common ten years ago
• Capillary tubing filled with nitrogen or helium
• reservoir pressure is measured at surface
• good for long term reservoir pressure monitoring
  of hot wells
• Electronic surface readout tool in thermal flask
• requires high temperature wireline
• Electronic memory tool in thermal flask
• state of the art
• slick line or braided cable

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WATER LEVEL
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SPINNER LOG

• Propeller measures flow in wellbore
• Identifies production (or injection) zones
• Calculate fluid velocity from series of up and
  down runs at different cable speeds

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TYPICAL SHALLOW WELL LOGGING UNIT
From USGS website, nc.water.usgs.gov
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TYPICAL SLICK LINE WINCH
From BOP Controls Inc. website, bopcontrols.net
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WELL INSPECTION LOGS

• Sonic Cement Bond Log (Same tool as sonic
  porosity log)
• Measures quality of cement on outside of casing
• Difficulty with large geothermal well casing
• Difficulty with micro-annulus caused by
  temperature and pressure changes
• Caliper
• Measures I.D. of casing
• Detects corrosion, scale, washouts, parted casing
• Electro-magnetic
• Measures metal loss
• Detects corrosion, holes and parted casing
• Ultrasonic (same as imaging tool)
• Measures I.D. and thickness of casing, and
  impedance of material behind casing
• Detects corrosion, holes and cement
• RA Tracer
• Injects slug of iodine 131 into wellbore
• Gamma ray detector measures radioactive slug
• Detects leaks in casing and flow behind pipe
• Video
• Identify well problems

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PRESSURE CONTROL

• Should be used there is any possibility of well
  flowing
• Pack-off
• Rubber cylinder tightens around wireline
• Few hundred psi
• Lubricator
• Length of pipe below pack-off
• Necessary to run tool in pressurized well
• Blow out preventor
• Valve below lubricator that closes around
  wireline
• Useful if pack-off fails or wireline gets stuck
  in pack-off
• Grease tubes for high pressure
• Placed below pack-off
• For thousands of psi
• Grease pumped in high pressure end flows to low
  pressure

Grease out Low pressure
Grease in High pressure
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PRESSURE-TEMPERATURE-SPINNER TOOLS FOR SALE

• MADDEN SYSTEMS (Odessa, TX)
• Flasked surface readout and memory tools
• KUSTER COMPANY (Long Beach, CA)
• Mechanical tools
• Flasked surface readout and memory tools
• Anyone with a slickline or braided cable winch
  can run memory tools.

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GEOPHYSICAL LOGGING TOOLS AND WIRELINE WINCHES
FOR SALE

• Companies that used to make tools and sell
  wireline systems went out of business in the
  1990s
• Companies that sell systems now are on the
  internet

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