the interval transit time of a compressional sound wave traveling through the formation along the axis of the borehole
Sonic log radius of investigation...
Sonic log measures _________ porosity
Sonic logs are optimistic/not optimistic in shaly sandstone
Modern sonic logs are what types of devices?
Borehole compensated (BHC)
Interval transit time is measured in...
microseconds per foot, the inverse of the velocity of a compressional sound wave in feet per second
The interval transit time is dependent on...
lithology and porosity
For sonic logs, porosity can be determined by chart or by these two equations...
Wyllie time-average equation and Raymer-Hunt-Gardner (RHG) equation
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
We can determine if a formation has vugs or fracture secondary porosity by...
subtracting sonic porosity by total porosity. (matrix-total=vuggy or secondary)
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
Radius of investigation of density logs is...
Density logs measure _______ porosity
Density logs are optimistic/not optimistic in shaly sandstone
What tow separate density values are used by the density log?
bulk density and matrix density
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
The number of returning gamma rays in the higher energy range is proportional to the...
electron density of the formation
The electron density that a density log measures is related to the...
formation bulk density
The bulk density that a density log measures is related to...
The response from the energy range in a density log is strongly dependent on _______ and only very slightly dependent on _______.
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
The photo-electric effect curve appeared as part of the second generation density tools, which are commonly reffered to as _____ or ______.
Formation bulk density is a function of _______, ______, and _______
matrix density, porosity, density of the fluid in the pores
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
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
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
Negative density porosity is often a good indication of the presence of ______ or other heavy minerals
Neutron logs are porosity logs that measure...
the hydrogen concentration in the formation
In clean formations where the porosity is filled with water or oil, the neutron log measures ______ _______ porosity
In a neutron log, energy loss can be related to the formation's _______
Neutron log responses vary, depending on (3 things)...
differences in detector types and what they detect, spacing between source and detector, lithology
The neutron log response is inversely proportional to _______
The sidewall neutron log is insensitive to lithologic effects, but sensitive to...
borehole effets such as rugosity
The most commonly used neutron log is the ________ ________ log
The advantage of compensated neutron logs over sidewall neutron logs is that they are less affected by...
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
An increase in neutron porosity due to the presence of clays is called
the shale effect
In a neutron log, whenever clays are part of the formation matrix, the reported neutron prosity is greater/less than the actual formation porosity
Resistivity logs are used to...(3 things)
determine hydrocarbon bearing vs water bearing zones, indicate permeable zones, determine porosity
As the hydrocarbon saturation of the pores increases, the formation's resistivity increases/decreases?
As the salinity of the water in the pores decreases, the rock's resistivity increases/decreases?
Old e-logs are ineffective in ______ and _______
salt mud, thin beds
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
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
Resistivity is measured by electric logs, commonly know as _______ (run in salt mud) and _______ logs (run in fresh mud).
The current can be produced and measured by either of two methods:
electrode tools (laterolog), induction tools
the most common type of electrical logging device in present use is the
The laterolog does not work in _____ ______ boreholes or ______ based muds.