A06_Specifications.docx

Specifications –

NEED - 2EMA-1000 EM39 electromagnetic induction probe - completely compatable with the Mount Sopris winches, loggers, and other tools we already possess. This is one part of a multipart logging system and it must be compatable with that system to work.

When attached to the necessary fully compatible Mount Sopris logging equipment the 2EMA-1000 EM39 probe measures the bulk conductivity of consolodated rock and unconsolodated sediments adjacent to the borehole. The electromagnetic induction method of measuring earth materials is now widely used for mapping ground water contamination plumes, for ground water exploration, and for general geological mapping. A logical extension to the surface geophysical method was the development of a borehole conductivity measuring probe. Although such devices (called induction loggers) have been used by the oil industry for many years their sondes are generally unsuitable for geotechnical application. For geotechnical work the principal requirements are:

1. slim probes, since the boreholes are often only 2 in diameter (usually PVC cased) .

2. excellent vertical resolution so that, for example, thin contaminant plumes can be accurately located and resolved.

3. high sensitivity combined with low noise and drift for measurements in resistive environments and also for detecting the small reductions in conductivity that are expected to occur when passing through contaminant plumes of organic liquids.

4. excellent long term stability so that repeated measurements in a borehole (for monitorig purposes) will detect the very small variations in conductivity with time that result from small changes in the nature and extent of the contaminant plume.

5. moderate depth of exploration, often only a few tens of meters and seldom greater than 200 meters.

2EMA-1000, probe indicates a tool with the Mount Sopris Instruments single conductor probe top attached

To create the 2EMA-1000 EM39 Mount Sopris modifies the EM39 probe with a V/F circuit board converting the analog voltage to an analog pulse, with 12,500 CPS as nominal “zero” and 17,500 CPS as nominal full scale. When the probe is in the 0 – 1000 mS/M mode, resolution is 5 CPS (hertz) per mS/M. This allows this probe to work with our existing geophysical logging systems. The 25 cm response is “bucked” so that the minimum radius of sensitivity is 4 inches, and the radius of maximum sensitivity is 28 inches from the axis of the borehole. There is a Century Geophysical LLC. 9512 Slim Hole Induction Tool that is similar, however, it is not designed for our logging system, and the range in the radius of measurement for that probe is listed as 10 to 50 inches. As can be seen this is different than that of the 2EMA-1000 EM39 or its predecessors design which has been used to collect 25 years of data. This would make the new data incompatible with the old data and negate the historical record. My market research identified no other probes that met the requirements.

The coil array in the induction probe has been designed so that it is not sensitive to material at a radial distance smaller than about 10 cm from the probe axis. The reason for this is to reduce sensitivity to the borehole fluid. The vertical resolution of the tool is 65 cm. This is measured as the vertical distance where the response is more than half the maximum response to an infinitely thin bed. The volume of investigation is similar to that of the 40 cm normal resistivity probe, therefore the induction tool and the normal resistivity tool give similar responses. The shape of the volume of the investigation is radically different between the two tools. See Geonics technical note TN-20 for more details on the theory of the induction logging and the response of the EM-39 conductivity probe.

The receiver circuit rectifies the received signal using a synchronous rectifier and generates two DC voltages, one proportional to the average value of the quadrature phase component of the received signal (with respect to the primary magnetic field), and another proportional to the in phase component of the received signal. The quadrature phase component is proportional to the conductivity and the in phase component is related to the magnetic susceptibility.

These DC voltages are then converted into pulse trains whose frequencies are proportional to the measurements. These pulses are sent up the logging cable for counting at the surface. The probe sends an ~ 12.5 KHz pulse train to indicate a measurement of zero, and ~ 17.5 KHz pulse train indicates a full, scale measurement. Positive pulses are sent and represent the millisiemens per meter (conductivity). Negative pulses are sent to indicate either the magnetic susceptibility if the tool is connected to a 2ADP-1000 adapter or the gamma count rate from the Poly - Gamma tool if the unit is connected to a 2PGA-1000.The reason a zero count rate of 12.5 KHz was selected is that in the presence of metallic objects negative readings occur. These objects are commonly smaller than the volume of the investigation of the probe, thus the mechanism used to subtract the primary field and the response from borehole fluid can cause negative readings. This can be useful information.

Range of measurement is controlled, by changing the gain of the receiver circuit. The gain can be changed manually in the probe or by applying different polarities to the probe for power. These polarities set a latching relay in the tool, which controls the gain setting. Only two different ranges are achievable by this method.

Controls for the induction probe consist of a rotary switch located inside the probe. To manually set this range switch you will need to open the probe by unscrewing the housing at the joint just above where the black heat shrink ends at the probe top. Remove housing and locate the range select switch using Figure 1. Set the switch as per Table 2. To have the tool select two ranges automatically refer to Table 3. Note that when the automatic selection is desired the switch must be set to position 5, for the surface equipment to be able to switch ranges in the tool. The factory setting is position 5, for the range switch.

Power Requirements D.C. voltage at probe top Min. 30 VDC Max. 80 VDC @ 50mA to 90mA depending on tool configuration

Cable Armor Negative and Pos, not polarity dependant Center conductor Pos and Negative, not polarity dependant Tool Output Pulse type, positive and negative going, 1.25uS wide from ~ 12.5 KHz to 17.5 KHz Radius of Investigation Radius of maximum sensitivity 28 cm Minimum radius of sensitivity 10 cm Vertical Resolution 65 cm Ranges or Scales 100mS/m, 1000mS/m, 10000mS/m Accuracy 5% of full scale Resolution

0.02 % of full scale Repeatability Listed as "+/- 2% full scale for temperature changes less than 10 degrees Centigrade" BUT WE ARE EXCEEDING THIS AS LONG AS WE HAVE BEEN GETTING THE EXACT SAME TYPE OF PROBE FROM MOUNT SOPRIS AND WE NEED TO KEEP EXCEEDING THESE SPECS.

Noise level Less than 0.5 mS/m Measurement point

91.4 cm (36”) from the joint of the probe top Temperature range -30 to 50 degrees Centigrade Operating frequency 39.2KHz Primary field source Self contained dipole transmitter Sensor Self contained dipole receiver Coil separation 50 cm Maximum depth 1000 m (water filled) Length 170 cm Diameter

3.65 cm Weight

3.2 kg (without weight section)