ISSN: 2578-4846
Authors: Ghosh S*, Milad B, Prasun S and Ghosh SS
Discontinuities are ubiquitous in all rocks at different scales. Their characterization occupies a high ground in the field of geological research. Discontinuity abundance, strength, flow and frictional properties are matters of great interest to structural geologists, petroleum engineers (mostly in unconventional shale gas and oil production), and civil engineers. Joints (opening mode fractures) are some of the most commonly observed rock discontinuities among others. Understanding joint origins from outcrops and other directly visible sources explain the presence of certain joints in the near and deep subsurface. We have summarized several tectonic and non-tectonic drivers behind joint origins and suggested the use of multiple supporting evidence while timing and causal interpretations are made. If particular subsurface joint sets may be traced back to the outcrops through the knowledge of their origins, their characteristics (length, aperture, height, abundance and interrelationships between these parameters) may be measured at the outcrops or using other data sources such as cores and image logs. Additionally, it is important to understand several non-visual data sources aiding in joint parameterization. This paper discusses the strengths and limitations of these direct (visual) and indirect (inference) data sources. In addition, we have summarized different methods for the quantification of the aforementioned joint related geometric and abundance parameters. We have shown that each measurement method and data source has its own set of strengths and limitations, and the appropriate methods to be used are case specific. We suggest that, if possible, characterization by direct visualization (mainly outcrops) should not be withheld or substituted with techniques that only imply the presence of joints and faults. Also, reconciliation of all joint-related parameters (i.e., geometry and abundance) from all available data sources provide confidence in the geologic interpretation and models.
Keywords: Fractures; Rocks; Joint characterization; Microseismic; Seismic; Satellite; Velocity anisotropy; LIDAR
