How can borehole geophysics be used to characterize subsurface structures?

1 Logging methods

One of the main borehole geophysical methods is logging, which involves lowering a device or a tool that records physical parameters along the borehole depth. Logging can measure properties such as electrical resistivity, natural gamma radiation, acoustic velocity, density, neutron porosity, magnetic susceptibility, and temperature. Logging can provide continuous and high-resolution data that can be used to identify and correlate subsurface layers, estimate rock and fluid properties, and detect anomalies or changes in the borehole environment.

2 Imaging methods

Another borehole geophysical method is imaging, which involves using a tool that produces an image or a map of the borehole wall or the surrounding formation. Imaging can use techniques such as acoustic, optical, electrical, or magnetic methods to generate images that show the shape, texture, orientation, and features of the borehole and the formation. Imaging can be used to characterize subsurface structures such as fractures, faults, joints, bedding planes, and borehole breakouts. Imaging can also provide information on the stress state, deformation, and fluid flow in the subsurface.

3 Crosshole methods

A third borehole geophysical method is crosshole, which involves using two or more boreholes that are connected by a source and a receiver of a physical signal. Crosshole can use signals such as seismic waves, electromagnetic waves, or heat to measure the properties and conditions of the formation between the boreholes. Crosshole can provide data on the spatial distribution and variation of subsurface structures and properties, such as velocity, resistivity, attenuation, anisotropy, and heterogeneity. Crosshole can also be used to monitor changes in the subsurface over time, such as fluid injection, extraction, or migration.

4 Integration methods

A final borehole geophysical method is integration, which involves combining data from different borehole methods or from other sources of geophysical data, such as surface or airborne surveys. Integration can enhance the resolution, accuracy, and interpretation of the borehole data by providing complementary or independent information on the subsurface. Integration can also help to reduce the uncertainty and ambiguity of the borehole data by using multiple lines of evidence and cross-validation. Integration can be done using various techniques, such as correlation, inversion, modeling, or visualization.

5 Here’s what else to consider

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