The Wireline Workshop bimonthly bulletin provides valuable information for wireline logging in the mining and mineral exploration industries. The July issue reviewed borehole navigation and verticality, borehole conditions and borehole fluid assessment. It also featured an overview of the Nuclear Magnetic Resonance (NMR) measurement and a guest article covering the principles and applications of Borehole Magnetic Resonance (BMR).
Wireline Logging – What does the Average Geo need to know?
Three basic topics for wireline loggers are covered in this issue. Guidelines are provided for less experienced loggers to make decisions for their surveys. Borehole navigation and borehole verticality are important properties in many industries. Typically, borehole logs should be precise but do not necessarily need to be accurate, however, borehole navigation does require an accurate log. The bulletin explains how it is difficult to assess accuracy when analyzing verticality logs. A main issue with this is that verticality logs are often reliant on magnetometers, which cannot be run through steel casing and have skewed results based on local magnetic material in the subsurface. Drift also affects the measurements. Refer to the full issue for a more detailed explanation of these problems and how they can be resolved.
The next topic that is described is the borehole condition. It suggests that knowing the condition that a borehole is in is vital before logging to prevent losing or damaging equipment. Running a “dummy” probe down the hole first can help you predict these conditions, as well as running a caliper tool to assess issues indicated by the borehole diameter. The last part of this section explains how properties of the borehole fluid provide useful information on your borehole or the surrounding material. The borehole fluid temperature, conductivity, flow and water quality can be measured with wireline logging. Certain tools can collect samples of the borehole fluid for further testing. The September issue of the Wireline Workshop will look at the physical properties of a formation.
Nuclear Magnetic Resonance
Each Wireline Workshop issue thoroughly reviews a wireline log measurement. The July issue describes nuclear magnetic resonance (NMR). This measurement does not require a radioactive source, but uses a strong permanent magnet and applies a secondary electromagnetic field to excite the source and collect data. This issue explains that NMR is useful to characterize porosity and infer permeability by measuring the rate of polarization and rate of decay. No other logging tool on the market currently provides such a reliable measurement. Although it is a more costly tool, it is eventually time and cost effective by preventing the need for additional surveying such as packer testing. This measurement is very useful for hydrological and geotechnical applications.
Borehole Magnetic Resonance
A guest article written by a scientist from NMR Services Australia (NMRSA) describes borehole magnetic resonance logging. Recently, Mount Sopris has added an NMR tool to our rental pool that was developed by NMRSA. This tool will be available for rental only and will come with full training from our experienced MSI staff. Refer to our recently added NMR page for more information on this tool. In this article, Tom Neville goes into depth on NMR physics and the theory of operation of a borehole magnetic resonance (BMR) probe.
The Wireline Workshop bulletins are aimed to provide expertise to wireline loggers in the mining and mineral exploration industries, however the content can be applied in many other industries as well. Subscribe here to receive this bimonthly bulletin. Click here to view and download the full July issue.