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2016-01-26 - Colloque/Présentation - communication orale - Anglais - 19 page(s)

Descamps Fanny , Fay Gomord Ophélie, Vandycke Sara , Van Landschoot Pierre, Leroy Yves, Caline Bruno, Schroeder Christian, Swennen Rudy, Tshibangu Katshidikaya , "Relations between lithology and geomechanical properties of chalks from NW Europe" in 5th International Geologica Belgica Meeting, Mons, Belgique, 2016

  • Codes CREF : Forages pétroliers (DI2324), Essais destructifs (DI2831), Sédimentologie (DI1415), Résistance et comportement des matériaux (DI2110), Mécanique des roches (DI1418)
  • Unités de recherche UMONS : Génie Minier (F408)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Ingénierie des matériaux (CRIM)
Texte intégral :

Abstract(s) :

(Anglais) High porosity pure white chalks have been extensively studied for more than forty years in relation with oil and gas production. Recently, there has been an increasing interest for unconventional reservoirs, among which other chalk formations, leading to the need for investigating a wider range of sedimentary systems. For a better understanding of their mechanical behaviour, a relation can be made with the diagenesis of chalk formations. Several classification systems exist for carbonates, based on their mineralogical content and their granulometry. Faÿ-Gomord (2014) developed a diagenesis index based on the evaluation of textural and diagenetic parameters: the micritic matrix texture, grains contact, coccolithe disintegration, cemented zone, automorphous cement crystals, coccolithe grain overgrowth and intraparticle cementation. This tool, especially developed for chalk, aims to quantify the global porosity reducing diagenesis affecting chalk microtexture. In this study, a wide variety of chalk samples from NW Europe have been investigated: classical high porosity chalk, clayey chalk, cemented chalk, coarse white chalk,… On the one hand, a petrographical and petrophysical study has been performed to determine their petrography, density, porosity, permeability and sonic velocity. On the other hand, uniaxial compression experiments have been performed. The dataset gathered on more than 30 samples covers a wide range of values for the determined properties: porosities range between 15 and 45%, strength between 3 and 50 MPa, just to give two examples. Additional data from literature are also considered in the study. The relations between petrographic and mechanical properties are investigated. The porosity-permeability relationship is found to be non-linear. Porosity is linked to P-wave velocity, strength and Young’s modulus: high porosity chalks have lower P-wave velocities and lower strength. In addition, the pore size shows an interesting relationship with the Young’s modulus. Finally, when assessing those relationships, chalk families based on their lithology can also be emphasized.