Tool table

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Development Geology Reference Manual
Series Methods in Exploration
Part Wireline methods
Chapter Basic tool table
Author Mark W. Alberty
Link Web page
Store AAPG Store

Logging tools are generally designed for operation under limited borehole conditions. A minimum hole size is the consequence of maximum tool diameter and pad curvatures, while maximum hole size is established by signal strength and caliper arm lengths. Mud types can affect signal transmission. Hole position affects signal strength and mud or borehole effects. Table 1 provides general operating limitations for the standard logging tools. Service companies have specially designed or modified tools that may allow extension of operation ranges.

Table 1 Basic tool tablea
Tool Minimum Hole Size (in.) Maximum Hole Size (in.) Mud Typeb Preferred Hole Positions Recommended logging speed (ft/hr)
F S B K O Excentered Stand-Off (in.) Centered
SP × NA
Gamma ray 6 20 <1800
Spectral GR 6 20 NRno report NRno report <900
Induction 6 20 × × 1.5 <3600
Laterolog 6 20 × × × <3600
Microresistivity 6 16 × <3600
Density 6 16 0–2.0 × <1800
IPL* 6 16 0–2.0 × 1800
Photoelectrical 6 16 × 0–2.0 × <1800
Neutron 6 16 × × <1800
Sonic 6 20 <3600
FWS (monopole) 6 20 × × <1800
Dipole 6 14 × <1400
Dipmeter 6 22 M × × <3000
Formation tester 6 16 NA NA NA NA
FMS 6 22 × × × <1800
Televiewer 6 14 × × <1200
FMI 6 21 × × × <1800
Pulsed neutron 2 12 <1800
CMR* 6.5 20 1800
aSymbols: √ = good conditions, × = unsuitable conditions, - = marginally acceptable conditions, NRno report = not recommended, NA = not applicable, M = with special modifications.
bMud types: F = freshwater (low salt), S = high salt, B = barite, K = high potassium salt, O = oil-based.
*Mark of Schlumberger

Computerized surface systems and cable communication systems have made tool combinations virtually unlimited. However, the combining of different tools into a single logging run may be limited by more than the physical ability to hook them together. Some devices are designed to operate excentered, some centered, and some stood off from the borehole wall. Tool positioning is important in ensuring valid environmental corrections. Table 1 includes optimum hole positions for each device. Caution should be used in combining a tool designed to be excentered, such as the neutron, with one designed to be centered, such as the sonic. The environmental effects upon the measurement may be uncorrectable. Also note that the maximum and minimum hole sizes are general recommendations only. Some logging devices are modified for larger and smaller holes.

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