No one will disagree that provisioning and planning for mining operations require accurate borehole survey tools that ensure quality control. Wrongly classifying a core sample location can lead to an economic or natural disaster.
We can all also agree on the knowledge that with millions of dollars invested in a mining operation, even the smallest error in a downhole survey tool's accuracy can cost precious time and significant amounts of money. In the drilling industry mistakes cost more than money; they can result in significant damage to a company's reputation or more importantly the environment.
The majority of drilling contractors rely on a borehole surveying instrument to make sure the drilling they undertake is as accurate as possible. Unfortunately, a large number are still using outdated or inferior downhole surveying technology. By understanding the benefits of the latest north seeking gyro technology, drilling contractors will be able to produce better results and increase profits.
Stockholm Precision Tools (SPT) is a downhole survey tool manufacturer which specialises in north seeking solid-state gyro tools and it was contacted by a client to verify an unexplained deviation of data taken from an alternative downhole gyro survey tool.
The being surveyed well was 543m with an inclination of -58.30 degrees measured from the horizontal. The alternative survey device lacked quality control features, which led to unquantified errors that would have resulted in the invalidity of the geological mapping of the mine.
That alternative tool attempted an in-run/out-run survey, which presented skewed results. To make sense of these results, SPT's north seeking GyroMaster borehole survey tool completed a separate run using its advanced continuous survey mode.
SPT's proprietary Navibore technology was instrumental in the tool's ability to produce highly accurate borehole survey data. Capable of surveying at high-speeds with no need to stop, this downhole technology allows SPT's continuous mode to register data points at every centimetre. This type of precision was crucial in producing definite survey data for this mining operation.
The comparison between the two tools used above highlight the advantages of north seeking technology and its ability to deliver the client precise survey results. Those advantages include: Increased accuracy, no need for topographic data, automated quality assurance, elimination of human error, and significantly reduced non-product time (NPT).
With the GyroMaster operating in continuous mode, it was three times faster than the alternative borehole survey tool. The GyroMaster took 105 minutes from the moment the drill machine was stopped until the drilling crew resumed drilling, providing two complete 550.06m independent downhole surveys logs for data interpretation and validation. The previous log completed by the alternative gyro downhole tool took 323 minutes to complete.
SPT's continuous survey mode was able to reduce NPT) for the drilling operation by over 3.5 hours. Such savings over the course of a year would make a significant saving and help increase the client's overall bottom line.
In addition, the north seeking borehole survey tool from SPT refers to a "true" north. Unlike the alternative gyro tool which was off the target by 60m, SPT's was not in need of declinations as it is oriented to an absolute reference direction.
SPT's Navibore technology allows for the downhole survey tool to automatically eliminate human error. This gives the GyroMaster the ability to find and correct itself along a borehole survey path, eliminating all possibility of drift. This tool does not need the collar azimuth, making it an absolute measurement without operator dependence.
The difference in accuracy between these two tools is vast. The alternative gyro survey tool showed an offset of six per cent in respect to the real bottom borehole emplacement; six per cent means 60m of uncertainty in a 1,000m hole. That is the equivalent of half a football (soccer) pitch. Compared to the pinpoint accuracy of the GyroMaster, which had a 0.1 per cent, which is the equivalent of only 1m of uncertainty in a 1,000m hole.
Data showing the extent to which borehole survey tool accuracy can differ
Choosing the right downhole gyro survey tool can help make a mining operation profitable. However, this is something that is sometimes easily overlooked. The comparison above demonstrates the importance of a borehole survey tool's accuracy for a mining operation. The data provided is essential to localise the core position in the three-dimensional global coordinates as an absolute system. Even a small error in accuracy could lead to the wrong calculation of natural reserves, which would prove to be disastrous for mine planning as ore could be considered waste rock because of a wrong localisation.
Another point to consider is that the direction of the downhole survey probe measured from the outside of the pipe is not the same as when measured inside the pipe. This is another source of error, which other downhole gyro survey tools often miss. From offering non-editable data to automated procedures which eliminate human error, SPT's quality assurance measures are unparalleled in the industry. All of our design, production and manufacturing is done in-house, to give us complete control.
