Zusammenfassung der Ressource
LECTURE 21
- WELL LOGGING
- Conventional Logs
- Spontaneous potential (SP)
- Measures natural
electric potential,
porosity, well correlation
- Resistivity (LLD and LLS)
- measure: electric resistivity,
deep+shallow logs (flushed
zone vs. virgin zone),
pemeability, pore fluid type
- Gamma-ray (GR)
- measure: decay of natural
radioisotopes, lithology, grain
size, well correlation
- Sonics (DT)
- Measure: slowness of
rock, lithology, porosity
- Caliper (CAL)
- Measure: borehole diameter,
washouts, mudcake,
stress-induced failure
- Neutron (NPHI)
- measure: hydrogen atoms (water
content), lithology, porosity
- Density (RHOB)
- measure: electron density, bulk
rock density, lithology, porosity
- Dipmeter
- measure: orientation of
dipping surfaces, structural+
stratigraphic analysis
- Measurement/logging
while drilling (MWD/LWD)
- log measurement detector
can also be mounted in the
drill colars behind bit
- Pros: real-time logging
while drilling, minimise
invasion effects, safer,
easier, possible in
horizontal/deviated well
- Cons: some not as
high quality as
wireline logging
- Measurement of physical
properties of rocks+fluids
vs. depth in a well
- many logs to identify rock
types, porosity, oil/water filled
- wireline logging
- housed in pipe (protection),
several assemble tools,
cable for power+send data
back
- data records as tool move
up+down holeat maintain
speed to measure depth
(200-2000m/hr)
- Logging truck
- mounted with cable, winch,
depth measurement +
computerise record +
processing equipment
- reading: measured property/volume (dimension of
volume control: resolution, radius of investigation)
- Specialist Logs
- High
resolution
electrical +
acoustic logs
- pseudo-images
of borehole walls
- high resolution image of
borehole: sedimentary
structure, fractures,
irregularities
- Small-scale structural +
stratigraphic analysis
- Stress-induced failure
of borehole (collapse)
- Drilling-induced
fractures (fluid loss)