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COMMERCIAL BOREHOLE LOGGING

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COMMERCIAL BOREHOLE LOGGING

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    1. COMMERCIAL BOREHOLE LOGGING PAUL SPIELMAN September 2007

    3. TYPICAL WIRELINE TRUCK

    4. TYPICAL WIRELINE SKID UNIT

    5. 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

    6. 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

    7. 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

    8. 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

    9. 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

    10. 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

    11. 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

    14. 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.

    15. 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

    16. 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

    18. TEMPERATURE PROFILE

    19. 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

    22. 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

    24. TYPICAL SHALLOW WELL LOGGING UNIT

    25. TYPICAL SLICK LINE WINCH

    26. 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 Requires very clear water

    27. 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

    28. 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.

    29. GEOPHYSICAL LOGGING TOOLS AND WIRELINE WINCHES FOR SALE Companies that used to make tools and sell wireline systems went out of business in the 1990’s Companies that sell systems now are on the internet

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