GEOPHYSICS (BOREHOLE) Flashcards
Drilled to study subsurface lithology along the path of a hole which can help interpret a 3D picture of the study area
Borehole logging
Process
1) Shallow NONCORE holes are excavated by reverse-circulation drilling
2) Deeper Holes are drilled by rotary drills with cutting units an tungsten-carbide or diamond bits
If a core barrel is recovered it is used for?
Lithology, Mineralization, and Structure Analysis
the process of using electric instruments to continuously measure the properties of a formation, in order to make decisions about drilling and production operations.
Wireline Logging
The cylindrical metal tube which houses the probe in borehole surveys
Sonde
How is data logging conducted in borehole?
Paper Strip and
Magnetic Tape in Analog
Properties obtained
1) Formation Thickness
2) Lithology
3) Porosity
4) Permeability
5) Proportion of Water and hydrocarbon saturation
6) Temperature
A postdiscovery method done by enhancing resisitivity contrast between the host rock and the sulfide ore which is indicative of mineralization continuity in strike, dip, shape and interconnectivity between numbers of intersections within a borehole
Mise a la Masse
“excitation of the mass”
Setup
positvie current electrode is planted into the condctive mass thrugh a pit or drill hole
what is the measured propoerty?
Surface potentials are measured with respct to the distant electrode and the distribution of which reflects the geometry of the conductive mass
Logs used to identify borehole size and shape
Caliper Logs
Logs used to differentiate sediments or sands
Lithology Logs
A scintillation detector that measures the Natural Radiation from a formation
Gamma Ray
A measurement vs depth of the potential difference between the volatage in the wellbore as a function of depth and that of an electrode on the surface
Spontaneous Potential
If the deflections in a log is towards the right the sediment is said to be?
Shale
If the deflections are to the left the sedment is said to be?
Sand
Logs that determine porosity and fluid types
Porosity logs
This measures tha bulk density of the formation (Rock and Fluid)
Density Porosity
Measures the hydrogen content in a porosity log
Neutron porosity
If there is a red line on the left of the black line, the porosity is
Highly Porous (Shale)
If there is a red line on the right of the solid black line, the porosity is
Low
When the red overlaps the black the lithology is
Wet Sand or Oil Sand
Logs that relate to seismic velocity
Velocity or Sonic Logs
Logs used to identify HC accumulation
Resistivity Logs
IN deep resistivity logs 4ft, high values mean
HC and Low Porosity
Low values means
Wet sand
If there is a separation between resistivities,
Formation fluid is different from the drilling fluid
Mise a la masse surveys
Geothermal Field
Pb Zn Cu
Au Pyrite
Conductive Ore
Miss a La masse
Mining and Econ Geol
?Electrical Mapping
?Mine Mapping
?Hydrocarbon mapping
?Extension of Ore bodies
?Base Metal w/ IP or EM
Mise a la masse
?Geothermal Field
?Pb-Zn-Cu
?Au-Pyrite
?Conductive Ore
Structural
?Demarcation of Geol structures and Intrusives
?Geochronology of Rock Formations
Hydrogeol
?Freshwater Resources
Environmental and Engg
?Engg Test Drilling
