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Home  >  Volume 46 (May, 2018)

42. ELASTIC PROPERTIES OF CLAY-DIAGENETIC SMECTITE AND KAOLINITE COMPOSITIONS OF SHALE by Aigba P. I., Nwankwo C.N. and Ijeh B.I. Volume 46 (May, 2018 Issue), pp305 – 312
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ELASTIC PROPERTIES OF CLAY-DIAGENETIC SMECTITE AND KAOLINITE COMPOSITIONS OF SHALE

Aigba P. I., Nwankwo C.N. and Ijeh B.I.

Department of Physics, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.

Department of Physics, University of Port Harcourt, Port Harcourt, Rivers State, Nigeria.

Abstract

The classical change associated with rocks of different constituents is an interesting concept that can be inferred using their elastic properties. The fluid contents, minerals and several geochemical processes heralding alteration of various mineral constituents and geometry of rocks are strong contributions to the stress associated with overburden, differential and fluid pressures. Obvious shifts in response of rock to stress, elastic moduli and of course Lame’s constant are characterized by different rock constituent and fluid substitution. The clay mineral of Kaolinite Dickite and Halloysite (KDH) on one hand and Illite-Smectite to Illite (I-S to I) alteration with its attendant free and interlayer bound water on the other hand makes it more interesting. The processes of quartz cementation involving dissolution, transportation of solute and precipitation all rolled into one helps to see permeability and porosity change. All these factors help to dictate the changing density, stiffness in other word the elastic properties of rock. Determining the elastic properties from all these activities are pointers to appreciating the geomechanics of the subsurface which are of the essence in reservoir study. Results of clay minerals were obtained from core sample of wells. Well logs were imported into the RokDoc software and correlated to results from core samples at corresponding depths with emphasis on shale formation as figured out from the Gamma ray log. Worthy of note is that some layers have Poisson ratio of over 0.4 with low moduli of elasticity indicating poor consolidation and probably appreciable smectite constituent. Other depths with high modulus of rigidity with higher I-S to I than KDH are of Illite dominance. Prior knowledge of clay mineral is essential in seismic modeling particularly in locating cap rocks relative to reservoirs.         

Keywords: Poisson ratio, Elastic moduli, Illite, Smectite, Permeability and Lame’s parameters.

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