Grade 10 Studying

Field Acceptance criteria for G
+- 2.5 milli G
FAC for B
+-6 counts or 300 nT (nano teslas)
FAC for magnetic dip
+- 0.45 degrees
working definitive surveys
most accurate description of the well path to present TD
final definitive surveys
most accurate description of the entire wellpath
Anticollision: classifying wells. What is the difference between single wells and nearby wells
Single well: at surface has separation of 41,000 ft + its own measured depth from all other wells

Nearby well: all wells that do not meet the criteria for a single well

Ellipsoids of uncertainty use what percent confidence?
These are calculated using error models, to a confidence of 95% in 3D
OSF?
Oriented separation factor, this is the method SLB uses unless there is a more conservative method used by the client. It does a scan, any well with an OSF less than 5 must be considered for a more detailed anticollision analysis.
Minor risk anticollision well
OSF between 1 and 1.5
Major risk anticollision well
OSF less than 1
MAS?
Minimum allowable separation
2 rules used to define MAS
Surface rule: single MAS is calculated at the well reference point, usually at surface, maximum 10 meters separation between wells.
OSF rule: the OSF between the planned trajector and all offset wells must be greater than 1.5 (not a minor nor a major OSF risk well)
Resistivity phase shift measurement limits
0.2 ohmm to 60 ohmm (for 2 MHz)
0.1 ohmm to 10 ohmm (for 400 kHz)
Resistivity attenuation measurement limits
0.2 ohmm to 25 ohmm (for 2 MHz)
0.1 ohmm to 3 ohmm (for 400 kHz)
Four Rules for Depth of Investigation
DOI increase with increasing resistivity
Attenuation measurements read deeper than phase shift
DOI increases with increasing transmitter spacing
400 kHz (lower freq) reads deeper than 2 MHz
Qualitative
Thinnest bed that the tool can detect (koala bears are thin)
Quantitative
thickness that the bed must be for the tool to read atleast 90% of its true resistivity value
Vertical Resolution
width at 50% of the vertical response function
Four Rules for Vertical Resolution
VR decreases with increasing resistivity
Phase shift measurements have better VR than attenuation
2 MHz (high freq) has better VR than 400 kHz (low freq)
VR remains constant for transmitter spacing