Downhole Surveys - DHS Australia

services

HSHA Rate Gyro - Calibration

DHS Calibration checks currently performed:

Downhole Surveys currently has in place a detailed calibration check procedure prior , during and after each survey. Monthly and other regular checks are preformed to ISO9002: 1994 Standards of Australia.

Manufactures Calibration
Each Gyro is factory calibrated and has its own personality file. This is done at least every two years in the Scientific Drillings' workshop based in the United States.

Field Calibration
The HSHA Rate Gyro is laid horizontally in an East/West plane. The tool is checked for horizontal with a precision spirit level. East /West is +- 10 degrees. The tool is allowed to reach optimum running temperature typically 90 - 100F. The latitude acquired from GPS is entered and this is used to calculate the Earth rate horizontal
15.0419 degrees per hour x Cos latitude.

The settle and fetch time for the tool is set at 18 seconds settle and 4 fetch.

Nine readings are taken and averaged in the East direction. The tool is then rotated 180 degrees and a further 9 readings are taken and averaged.

The tool bias's DI and DS are recorded and updated. Any large shifts in these values will indicate the tool should be recalibrated.

End of hole Gyro compass check/validation
At the completion of every hole surveyed in high speed mode an independent Gyro Compass reading is taken to check and validate the High speed survey. Acceptance is +- 0.5 degrees. Azimuth. Gyrocompass check readings are available with every survey in a hard copy print format.

Earth rate horizontal (ERH) readouts
After each gyrocompass shot, the operator checks the earth rate horizontal readout on the printer. The computer calculates this reading using the formula lat(cos) x 15.041= expected ERH to calculate the azimuth. If this reading is out by more than +- 0.5% another shot is taken.

Example of test stand simulation
Below is an example of the results achievable from the HSHA Gyro in a simulated drill hole with azimuth 270 and dip angle +2 degrees.

HSHA Gyro		ID: HSS133	21/04/01
Tilt	Azimuth	Tool Stand	Difference
(deg)	(deg.)	Azimuth	Azimuth
92.35	270	270	0
92.37	270
92.36	270
92.34	270.9	271	-0.1
92.32	270.9
92.34	271.9	272	-0.1
92.34	271.9
92.31	272.92	273	-0.08
92.35	272.92
92.35	273.93	274	-0.07
92.33	273.93
92.35	274.93	275	-0.07
92.31	274.93
92.33	273.97	274	-0.07
92.33	272.98	273	-0.02
92.32	272.98
92.33	271.98	272	-0.02
92.32	271.98
92.35	270.98	271	-0.02
92.33	270.98
92.33	269.99	270	-0.01
92.33	269.98
92.36	269.98	Tilt Positive	Tilt
92.36	269.98	92.3	0.06
92.34	269.98
93.33	269.98	93.3	0.03
93.33	269.98
93.34	269.98
94.33	269.97
94.35	269.97	94.3	0.05
94.33	269.97
94.32	269.97
95.32	269.96	95.3	0.02
95.31	269.96
96.30	269.96	96.3
96.29	269.96
96.28	269.96

Below is an example of the end of hole Gyro compass Vs high Speed survey.

Depth	Tilt	Azimuth	Gyro temp
	(deg.)	(deg)	(F)
High Speed mode
-200	32.40	38.54	89.74
-205	32.46	38.54	89.74
-210.1	32.51	38.64	89.79
-215	32.53	38.72	89.83
-220	32.55	38.76	89.83
-225.1	32.48	38.87	89.84
-230	32.49	38.93	89.90
-230.1	32.50	38.92	89.90
-230.1	32.53	38.92	89.90
-230.1	32.52	38.92	89.88
Gyro Compass
230.1	32.52	39.08	90.08
QC Check (variation)	0.00	0.08

	SERVICES LINKS
	HSHA Rate Gyro In Rods RC/DDH holes PVC cased holes Horizontal holes Steering/Orientation in vertical holes Steering and directional surveying Calibration Tech Specs on HSHA Rate Gyro Electronic Multishot Open holes Blast holes Grade control Component Downhole Magnetic Surveying Surveying through DDH bit Inside RC rods Tech Specs on Multismart

MANUAL TEST STAND CALIBRATION CHECK

Calibration check stand - Kalgoorlie W.A.

Gyro Compass Mode
A precision check stand has been built at our Kalgoorlie office and provides checks on the survey equipment. Gyro compass mode is checked against a range of inclinations and azimuth headings, fully exercising the tool. Typical tolerances are +- 0.02 degrees inclination and +- 0.1 degrees Azimuth.

Drill hole simulation
The calibration jig allows us to simulate any drill hole and check the accuracy of each individual tool, thus optimising the performance of a particular tool prior to completing the project.

MANUAL TEST STAND CALIBRATION CHECK

Calibration check stand - Kalgoorlie W.A.

High Speed mode
Utilising our precision test stand, based in Kalgoorlie, a deviating drill hole is simulated and surveyed in high speed mode to test the performance of the HSHA Rate Gyro in extreme deviation situations. This test stand will enable Downhole Surveys to calculate accurately the tool uncertainty for any given drill hole simply by simulating the deviation of each hole with the test stand. Any errors no matter how small are mapped, providing end of hole uncertainty data.

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