Clay minerals used in stratigraphical correlations of coal-bearing carboniferous formations
The main objective of this research project has been the development of a new tool for the lithostratigraphical correlation of cored boreholes. Over 1000 samples (mainly from mudstones, some siltstones and sandstones) have been taken out of the cores, at a regular spacing (about 2 m), for further mineralogical analysis. Simultaneously, a sedimentological study has been carried out on the sampled sequences, as well as a petrographical analysis of the main rock types. The mineralogical composition of the clay has been identified by X-ray diffraction methods. The qualitative and semi-quantitative changes of these clay minerals revealed by specific post-treatment, as well as those of the intensity ratios of some particular diffraction peaks, display characteristic trends within coeval rock sequences from different boreholes. The computer-aided graphical processing of these parameters produced percentage or intensity ratio curves, which could then be used as a lithostratigraphical correlation tool. These graphs show strong similarities with geophysical well-logging graphs. The general aspect of the graphs is studied, and more especially the presence of minima and maxima, as well as their varying intensities (amplitudes). Successful correlations were established between relatively simple rock sequences (without split seams) in neighbouring boreholes (1 to 3 km apart). Then positive correlations were achieved between more complex sequences containing multiple coal seams, and finally some positive but less obvious correlations were established between sequences from widely spaced boreholes (+/- 10 km).
Bibliographic Reference: EUR 14024 FR (1992) 173 pp., MF, ECU 8, blow-up copy ECU 27
Record Number: 199210600 / Last updated on: 1994-12-02
Original language: fr
Available languages: fr