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The sonic log measures...
the interval transit time of a compressional sound wave traveling through the formation along the axis of the borehole
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Sonic log radius of investigation...
5-6 inches
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Sonic log measures _________ porosity
matrix
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Sonic logs are optimistic/not optimistic in shaly sandstone
optimistic
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Modern sonic logs are what types of devices?
Borehole compensated (BHC)
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Interval transit time is measured in...
microseconds per foot, the inverse of the velocity of a compressional sound wave in feet per second
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The interval transit time is dependent on...
lithology and porosity
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For sonic logs, porosity can be determined by chart or by these two equations...
Wyllie time-average equation and Raymer-Hunt-Gardner (RHG) equation
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Porosity values are too high/low when sonic porosities of carbonates with vuggy or gracture porosity are calculated by the Wyllie formula and why
low because the sonic log only sees matrix porosity
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We can determine if a formation has vugs or fracture secondary porosity by...
subtracting sonic porosity by total porosity. (matrix-total=vuggy or secondary)
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The interval transit time is increased due to the presence of...
hydrocarbons, if the effect of hydrocarbons is not corrected, the sonic derived porosity is too high
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Radius of investigation of density logs is...
2 inches
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Density logs measure _______ porosity
total
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Density logs are optimistic/not optimistic in shaly sandstone
not optimistic
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What tow separate density values are used by the density log?
bulk density and matrix density
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What is done to compensate for the shallow depth of investigation of a density log?
the tool is held against the side of the borehole during logging
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The number of returning gamma rays in the higher energy range is proportional to the...
electron density of the formation
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The electron density that a density log measures is related to the...
formation bulk density
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The bulk density that a density log measures is related to...
porosity
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The response from the energy range in a density log is strongly dependent on _______ and only very slightly dependent on _______.
lithology, porosity
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The DRHO curve indicates what?
how much correction has been added to the bulk density curve during processing due to borehole effects and is primarily used as a quality control indicator
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The photo-electric effect curve appeared as part of the second generation density tools, which are commonly reffered to as _____ or ______.
Litho, Spectral
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Formation bulk density is a function of _______, ______, and _______
matrix density, porosity, density of the fluid in the pores
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In a density log, if the formation's actual matrix density is less than the matrix density used to calculate porosity, the log shows a calculaed porosity that is higher/lower than the actual porosity of the formation
higher
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In a density log, if the formation's actual fluid density is less than the fluid density used to calculate the porosity, the log shows a calculated porosity that is higher/lower than the actual porosity of the formation
higher
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In a density log, where invasion of a formation is shallow, the low density of the formation's hydrocarbons causes the calculated density porosity to be greater/less than the actual porosity
greater
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Negative density porosity is often a good indication of the presence of ______ or other heavy minerals
anhydrite
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Neutron logs are porosity logs that measure...
the hydrogen concentration in the formation
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In clean formations where the porosity is filled with water or oil, the neutron log measures ______ _______ porosity
liquid filled
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In a neutron log, energy loss can be related to the formation's _______
porosity
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Neutron log responses vary, depending on (3 things)...
differences in detector types and what they detect, spacing between source and detector, lithology
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The neutron log response is inversely proportional to _______
porosity
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The sidewall neutron log is insensitive to lithologic effects, but sensitive to...
borehole effets such as rugosity
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The most commonly used neutron log is the ________ ________ log
compensated neutron
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The advantage of compensated neutron logs over sidewall neutron logs is that they are less affected by...
borehole irregularities
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In a neutron log, whenever the pores are filled with gas rather than oil or water, the reported neutron porosity is less/more than the actual formation porosity
less
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An increase in neutron porosity due to the presence of clays is called
the shale effect
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In a neutron log, whenever clays are part of the formation matrix, the reported neutron prosity is greater/less than the actual formation porosity
greater
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Resistivity logs are used to...(3 things)
determine hydrocarbon bearing vs water bearing zones, indicate permeable zones, determine porosity
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As the hydrocarbon saturation of the pores increases, the formation's resistivity increases/decreases?
increases
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As the salinity of the water in the pores decreases, the rock's resistivity increases/decreases?
increases
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Old e-logs are ineffective in ______ and _______
salt mud, thin beds
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In log interpretation, the _________, the ______, and the _____ ____ of the formation are
all assumed to have a high resistivity (low conductivity) to electric current flow.
hydrocarbons, rock, fresh water
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Resistivity is a basic measurement of a reservoir’s fluid saturation, and is a function of _______,
______ of ______, ______ of _______, and ______ of _______.
porosity, type of fluid, amount of fluid and type of rock
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Resistivity is measured by electric logs, commonly know as _______ (run in salt mud) and _______ logs (run in fresh mud).
laterologs, induction
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The current can be produced and measured by either of two methods:
electrode tools (laterolog), induction tools
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the most common type of electrical logging device in present use is the
induction tool
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The laterolog does not work in _____ ______ boreholes or ______ based muds.
air filled, oil
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The laterolog works best in...
salty mud
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The dual laterolog consists of a...
deep reading measurement (RLLD), shallow reading measurement (RLLS), microspherically focused (RMSFL)
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The microspherically focused resistivity log (RMSFL), is a ____-_____, focused electrode log that has a very shallow/deep depth of investigation.
pad-type, shallow
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induction logs work well in wells containing ________ in the borehole such as air and oil-based muds and freshwater muds
non-conductive fluids
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Induction logs are affected most by...
salty muds
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Induction logs work best in ____ to ______ formation resistivities
low, moderate
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The short normal works best in
freshwater muds
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What does the FF in 6FF40 mean?
The FF in 6FF40 means that the tool is focused both radially and vertically
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The dual induction consists of...
a deep-reading device which attempts to measure Rt and a medium-reading device which measures Ri
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Neutron Logs radius of investigation is...
6 inches
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What type of Porostiy does the Neutron Log measure..
Total
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Neutron logs are optimistic/not optimistic in shaly sandstone
optimistic
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What four curves have we discussed that the density log can give us?
- Correction curve for density (DRHO)
- Density derived porosity (DPHI)
- Photo Electric (PE)
- Bulk Density (RHOB)
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What two things can be determined from crossplots?
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Density logs can assist the geologist by? (4)
- Identify evaporite minerals
- detect gas bearing zones
- determine hydrocarbon density
- evaluate shaly sand reservoirs and complex lithologies
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Four combinations of porosity measurements?
- Neutron vs density porosity
- Neutron vs. Sonic Porosity
- Sonic vs Density
- Spectral vs Density
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3 ways that permeability can be indicated on a microlog/sp/caliper combinations log?
- R2>R1x1 micronormal is greater than microinverse
- Decrease in borehole size
- Detection of mudcake
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When the ILD is corrected for invasion, it will always yield an Rt that is more than or less than the ILD reading?
Lower for deep induction (higher for deep laterlog)
WHY! I dont know
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The two resistivity measurements made from a microlog are?
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What three logs were designed to measure resistivity in the flushed zone,rxo?
- Proximity
- Microlaterolog
- Micro Spherically Focused
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What 2 variables affect the Laterolog?
- Formation Thickness
- Borehole Size
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Induction logs measure formation ______ rather than _______
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the most important use of resistivity logs?
•determination of hydrocarbon- bearing vs. water-bearing zones.
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The Dual induction log is useful in formations that are deeply invaded by
Mud filtrate
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What adversely affects the measurement of a microresistivity device _________-and _________?
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Nonporous and impermeable zones have high/low resistivity values on both the micronormal and microinvers curves?
High
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The microlog does not work well in Salt/Fresh water muds?
Salt
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the microlaterlog should be run only in salt water muds
thats the answer
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Proximity log should be run in fresh/salt water muds?
Fresh
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Measurements of a formations resistivity close to the borehole is used to determine?
Porosity
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