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Hydraulic cut-off and gas recovery potential of sandstones from Tight Gas Reservoirs: a laboratory investigation

type de publication      communication internationale avec actes publiés
date de publication 28-06-2011
auteur(s) Jeannin Laurent; Davy Catherine A.; Skoczylas Frédéric; Portier Eric; Fu Xiaojian; Agostini Franck
conférence 45th US Rock Mechanics / Geomechanics Symposium 2011
     dates de 26-06-2011 à 29-06-2011
     lieu San Francisco, California, USA
     nom des actes Proceedings of the American Rock Mechanics Association's 45th U.S. Rock Mechanics / Geomechanics Symposium
  Sous presse
résumé Our experimental study relates to several sandstone samples originating from a tight gas field explored by GDF/Suez. The aim of the study is to characterize experimentally the petro-physical properties of these materials, in order to improve our knowledge on their gas recovery potential. The initial characterisation of these sandstone samples is performed in the dry and in the “as received” states: porosity, initial water saturation level, gas permeability at Pc=5MPa confining pressure. Further, sandstone samples have been preserved into hermetic chambers at fixed relative humidity (RH) values, until mass (and water saturation level) stabilisation. Gas permeability is measured at stabilisation, from 5 to 40MPa confinement. This method is limited to Sw ≤ 21%. In order to reach higher water saturation levels Sw, an iterative method has been developed, which allows to reach values as high as 70%. For two different samples, we have evaluated the water saturation threshold above which no more gas passes through the porous network, due to hydraulic cut-off, under increasing Pc. At intermediate saturation level (on the order of 40%), two different sample types have been identified, depending on whether their gas relative permeability depends, or not, on Pc. For one sample of each type, poro-elastic experiments provide drained bulk modulus Kb and solid matrix bulk modulus Ks, from which Biot’s coefficient b is deduced. From these tests, we show that the closure of some portion of the connected porous network is bound to explain the sensitivity of sandstone permeability to confining pressure.
mots clés tight gas sandstone, desorption isotherm, permeability, poroelasticity, SEM
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