Module 1- Log Analysis Findamentals Flashcards
What 3 things do we need to find out in a well log?
Rock Type, Rock Properties, Fluids
What is a well log?
A continuous record of measurements made in bore hole to detect variations of some physical properties of the subsurface rocks.
What are the 5 properties of the rock that logging is trying to determine?
Porosity Permeability Bedding Orientation Fractures Temperature
What are the 4 fluid properties logging is trying to determine?
Type
Saturation
Salinity
Pressure
What information can be determined from drill cuttings?
rock type
HC indications
Porosity type
What information can be determined from mud logs?
drilling rate
mud properties
gas analysis
What information can be determined from pressure transient tests?
reservoir pressure
permeability and skin
fluid recovery
What information can be determined from cores?
porosity
permeability
lithology
residual fluid saturations
What information can be determined from well logs?
Porosity
lithology
water saturation
net pay thickness
What information can be determined from Seismic data?
structure
gross and net thickness
porosity
What is the only logging method that is considered to have definitive results?
Cores!
Open hole logging tools are also called?
Sondes
what are triple-combo & platform Express tools?
Modern wireline logging tools that run resistivity and porosity tools at the same time.
Triple combo-90ft
platform express- 38ft
The triple-combo & platform express tools each contain what?
Resistivity Log
Two porosity logs
What are passive measurements?
may be made of naturally occurring phenomena like radioactivity
What are active measurements?
may be induced, as is the case with an induction resistivity log, for example.
What are the 3 broad categories of open hole logs?
Natural detection
Porosity
Resistivity
What are the 2 natural detection logs?
Spontaneous Potential
Gamma Ray
What does Spontaneous Potential measure?
Measures natural electric potential generated in the rock, showing porous and permeable beds.
SHALE OR NON-SHALE INDICATOR
what do Gamma Ray logs measure?
measures natural radiation from unstable elements (uranium, thorium, potassium)
What would a good gamma ray lithology log read?
identifies shale clearly by HIGH gamma ray readings.
identifies Sandstone & carbonates by LOW gamma ray readings.
What are the 3 logs used to calculate porosity?
Neutron (emits neutrons)
Density (emits gamma rays)
Sonic (emits sound waves)
What does a neutron log measure?
Hydrogen concentration in the formation
What does a density log measure?
measures the weakening of gamma rays and calculates bulk density of the formation
What does a sonic log measure?
transit time of sound waves through formation
Define resistivity
ability of a material to resist electrical conduction. Inverse of conductivity. Measured in Ohm-m.
What are the 2 resistivity logs?
Induction log
Laterolog
What does an induction lot measure?
measures resistivity indirectly by measuring conductivity
What does a laterolog(focused log) measure?
measures resistivity of formation by passing a current between two electrodes.
T or F: The induction and Laterolog are commonly run together?
TRUE
What do the following abbreviation stand for? (terminologies used in a borehole environments/well logging)
dh di/dj Rmf Rxo Sxo Rw Rt Sw
dh- hole diameter di/dj- invasion diameters Rmf- mud filtrate resistivity Rxo- flushed zone resistivity Sxo- flushed zone saturation Rw- formation water resistivity Rt- uninvaded zone resistivity Sw- water saturation
What are 6 things that open hole well logs are used for?
- Detect hydrocarbons
- Determine lithology
- Evaluate zones
- Correlation zones
- Determine dip, faults and other geologic structures
- identifies sedimentary environments of deposition
Explain methods used in both open hole and cased hole well logs.
Open hole logging tools are attached to a wire-line and run to the bottom of the hole. The tool is slowly pulled upwards and the tool response is sent through the wireline to the truck where it is recorded.
Alternatively, the logging sensor may be embedded in the drill string and is LWD.
What is high-tension conveyance & wireline deployment and why is it used?
condition associated with deep, highly deviated well paths that are managed by using systems that pair high-stregth cable with specialized surface equipment.
conveyance of most logging tools on drill-pipe, coiled tubing or wireline tractors is also available
