The analysis of cores and cuttings starts with the observation and description of the geological samples taken during well drilling. Rock type, color, hardness, characteristics of materials filling fractures (cores only), degree and condition of alteration etc., are the main items to describe. To make a more precise description of the type of rocks, thin sections of cores and cuttings are prepared and subject to microscope observation. Following, the geologic column (Fig.1-1) of the wells under study are prepared to disclose the rock type and stratigraphy (Fig.1-2) around the geothermal well.

In West JEC we are careful in pursuing the exact degree of geological detailing to avoid unnecessary work and acquisition of information. Precisely, the description of the well geology is completed with the least number of formations that clearly identify the rock type or age. Also, we are careful to give priority to the determination of boundaries between geological formations through the comparing of geologic formations and geological boundaries in order to improve the disclosure of faults (Fig.1-3).

 

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Fig.1-1 Example of the geological column of a geothermal well
Fig.1-2 Example of the stratigraphy of the geothermal field
Fig.1-3 Geological cross section of the Hatchobaru geothermal field
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