The Research On Identification Of Fluid Properties And Classification Of Tight Gas Sand Reservoirs

Tight sandstone gas belongs to unconventional petroleum resources. It has uniquecharacteristics, such as small reservoir pore space, poor percolation capacity, strongheterogeneity, complex pore structure, changes in lithology and electrical, complexrelationship between gas and water, low gas saturation, fluid identification difficulties. Howto effectively evaluate tight gas sand reservoirs with the logging data has great significance ofexploration and development.The tight reservoir lithological characteristics, physical properties and pore structurecharacteristics are analyzed through collecting the data of the study area in this thesis. Inconnection with characteristics of tight gas sand reservoir, the reservoirs macro-parametermodel of porosity, permeability and bound water saturation calculated by T2cutoff value arestudied with the NMR logging. According to the theoretical basis that NMR T2spectrum andmercury injection capillary pressure curve both can reflect of the pore size, a similar contrastmethod calculated transverse conversion factor and a segmented equal-area method tocalculate the longitudinal conversion factor are discussed. Then NMR T2spectrum isconverted into a pseudo-capillary pressure curve, and the microscopic pore structurecharacteristic parameters of reservoir are calculated. In accordance with the standards ofoilfield production, the study area reservoir is divided into three classes. Combined with thereservoir macro and micro parameters, five parameters such as the effective porosity,permeability, irreducible water saturation, expulsion pressure and pore throat radius arescreened to construct a complex sub-index of the reservoir which is used to divide reservoirtypes. Development process of water saturation model for decades is researched. On the basisof previous studies, the three-component mixed-linked conductive saturation model isproposed. In connection with the problem that the tight gas sand reservoirs has complexrelationship between gas and water and difficult fluid identification. Three methods such as overlapping double-saturation method overlapping shear wave time difference method basedon longitudinal wave time difference and the method based on building a gas spectral libraryare used to identify fluid properties which better results are achieved.