A038 Guard Tool 38mm

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Tool Description

The A038 Guard tool is designed for the measurement of electrical conductivity of rocks in boreholes. This tool requires the presence of conductive fluid and the absence of casing. The tool is capable of providing measurements under adverse conditions, such as where high borehole fluid salinity and resistive formations cause normal resistivity logs to show poor results. Good vertical resolution and depth of investigation facilitate the detection of fractures, permeable zones, formation, water quality and strata correlation between boreholes.

The purpose of the Guard Log is to measure resistivity or its inverse, conductivity, in order to calculate porosity and to interpret lithology. The Guard Log is useful in several types of ground investigation and is more suitable than other resistivity measurements in high conductivity fluids and when vertical resolution is important.

This tool is also available in combination with Natural Gamma. Click here for more information.

Mineral Investigation

The resistivity of rocks depends on several factors. Rocks are usually poor conductors. Rock resistivity is determined, primarily, by porosity and the salinity of the pore fluid.

Clay minerals reduce the resistivity of the formation. Some alteration processes result in the formation of clay minerals, reducing resistivity, while others reduce rock porosity and increase formation resistivity. Decreases in resistivity may be a result of either significant concentration of conductive metal sulphides or oxides. Fracturing increases effective porosity and can, therefore, decrease resistivity.

The complexity of resistivity interpretation means that complementary information from other geophysical measurements or other geological logs is usually required. However, massive sulphide deposits generally consist of conductive ore zones and resistivity logs are often used to delineate these ore zones.

Coal Investigation

Coal usually has high resistivity. This may be reduced according to its porosity, clay, and water content. The porosity of coal varies with rank and so its resistivity increases from lignite to semi-anthracite and then decreases slightly with anthracite. Clay inclusions reduce the resistivity of coal.

Clay-rich lithologies, such as shales, have low resistivity. Clean, relatively dry sandstone has high resistivity. This may be reduced according to porosity, salinity, and clay content.

Resistivity (or conductivity) logs may also indicate oxidation of a coal seam or alteration by an intrusion.

Ground-water Investigation

The Archie equation defines the relationship between porosity and resistivity in reservoir rocks:

F = Ro / Rw where;

Ro = resistivity of a clean formation
Rw = resistivity of the water saturating the rock
F = a constant of proportionality called the formation factor

FEATURES
Convenient and simple to use
High sensitivity
MEASUREMENTS
Resistivity or Conductivity
APPLICATIONS
Coal, Ground Water	Mineral detection
OPERATING CONDITIONS
Borehole type	Borehole type: open-hole, water-filled
TOOL SPECIFICATIONS
Diameter	38 mm / 1.496 in
Length	1800 mm / 70.866 in
Weight	6 kg / 13.227 lb
Min. Temperature	0ºC / 32 ºF
Max. Temperature	70ºC / 158ºF
Max. Pressure	15 000 kPa / 2175 psi
Tool Voltage Required	30 VDC
Tool Current Required	45 mA
Communications	Pulse
Cable Conductors Required	1 or 4
SENSORS
Guard
Guard Electrode Length	800 mm / 31.496 in
Sense Electrode Size	100 mm / 3.937 in
Excitation	250 Hz - 9V positive square wave
Conductivity Range	0.1 - 200 mS/m
Accuracy	5% FSD
SHIPPING SPECIFICATIONS
Length	2000 mm / 78.740 lb
Width	120 mm / 4.724 in
Height	120 mm / 4.724 in
Weight	8 kg / 17.636 lb
SALES INFORMATION
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