Geologica Belgica

1374-8505 2034-1954

 

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Karl-Heinz A.A. WOLF, Dan BOSSIE-CODREANU, Rudy EPHRAIM & Nikolai SIEMONS

ANALYSING CLEAT ANGLES IN COAL SEAMS USING IMAGE ANALYSIS TECHNIQUES ON ARTIFICIAL DRILLING CUTTINGS AND PREPARED COAL BLOCKS

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Annexes

Mots-clés : Coal, Cuttings, Image Analysis, Cleat, Angle Distribution, CT-scan.

Abstract

For coal seams, considered as gas reservoirs, the orientation of the major cleat directions are dominating the flow direction and control the Darcy permeability. Information on the intra-cleat angles is obtained from coal fragments, which simulate drill cuttings. The methodology here below describes the use of image analysis techniques to determine from cuttings the intra-cleat angle and the angles between the cleats and bedding. The analysis is based on the phenomenon that cleats and bedding planes form the weakest bounds in a coal bed. Up to two thousand fragments, of three French coal samples, are analysed to characterize a cleat angle distribution for each coal. After the extraction of the (sub-) spherical fragments, shape factors are calculated for the fragments left behind. These shape factors act as a second filter, which remove grains with no rectangular or parallel like shape. The relationships between measured spatial properties are summarized into frequency histograms, which give a picture of the most abundant face angles in the accepted fragments. The resulting histograms are compared with 3D cleat angle reconstructions of the same coal samples, obtained from CT-scans. These scans are analyzed on their fracture patterns in three orthogonal directions. Here the results are from macro-cleat spacings with a larger cleat distance than obtained from the fragments.

To cite this article

Karl-Heinz A.A. WOLF, Dan BOSSIE-CODREANU, Rudy EPHRAIM & Nikolai SIEMONS, «ANALYSING CLEAT ANGLES IN COAL SEAMS USING IMAGE ANALYSIS TECHNIQUES ON ARTIFICIAL DRILLING CUTTINGS AND PREPARED COAL BLOCKS», Geologica Belgica [En ligne], volume 7 (2004), number 3-4 - Proceedings of the 5th European Coal Conference, 105-113 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=246.

About: Karl-Heinz A.A. WOLF

Delft University of Technology, Department of Applied Earth Sciences, Dietz Laboratory, Mijnbouwstraat 120, 2628 RX Delft, the Netherlands. E-mail: k.h.a.a.wolf@ta.tudelft.nl

About: Dan BOSSIE-CODREANU

Institut Francais du Petrole, 1- 4 Avenue de Bois-Preau, BP 311 – 92506 Rueil-Malmaison, Cedex – France. E-mail : Dan.Bossie-Codreanu@ifp.fr

About: Rudy EPHRAIM

Delft University of Technology, Department of Applied Earth Sciences, Dietz Laboratory, Mijnbouwstraat 120, 2628 RX Delft, the Netherlands.

About: Nikolai SIEMONS

Delft University of Technology, Department of Applied Earth Sciences, Dietz Laboratory, Mijnbouwstraat 120, 2628 RX Delft, the Netherlands.