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Wladyslaw Altermann - One of the best experts on this subject based on the ideXlab platform.

  • Calculation of water saturation in low resistivity gas reservoirs and pay-zones of the Cretaceous Grudja Formation, onshore Mozambique basin
    Marine and Petroleum Geology, 2015
    Co-Authors: Vincent Mashaba, Wladyslaw Altermann
    Abstract:

    Abstract The water saturation of a hydrocarbon bearing formation is usually calculated via the conductivity of the formation water, as defined by Archie, 1942. However, in some formations such conventionally calculated water saturation contradicts values calculated from the Nuclear Magnetic Resonance (NMR) tool and from the Drill Stem Test (DST). Here we discuss such a case of low resistivity pay zones in the J- and K-Reservoirs, of the Lower Grudja Formation of Maastrichtian age, onshore Mozambique basin, in which conventional log analysis contradicts water saturation calculated from the NMR and by the Drill Stem Test. For both, the J-Reservoir and K-Reservoir, the water saturation (Sw) was calculated using the Archie Equation and the Simandoux Equation, that accounts for clay bound water but not for silt, and the results were compared to NMR-calculated water saturation. A new algorithm that improves the accuracy of water saturation calculation was introduced. This new algorithm takes into account the clay- and silt-bound water within the overall reservoir resistivity. It is demonstrated that the clay- and silt-bound water must be included in water saturation calculations, where the formations are rich in silt and clay. The Simandoux Equation and the new algorithm yield significant improvement in water saturation results for the J- and K-Reservoirs, when compared to water saturation calculated using the Archie's Equation.

Christos D. Tsakiroglou - One of the best experts on this subject based on the ideXlab platform.

  • The correlation of the steady-state gas/water relative permeabilities of porous media with gas and water capillary numbers
    Oil & Gas Science and Technology - Revue d'IFP Energies nouvelles, 2019
    Co-Authors: Christos D. Tsakiroglou
    Abstract:

    The steady-state gas, k rg, and water, k rw, relative permeabilities are measured with experiments of the simultaneous flow, at varying flow rates, of nitrogen and brine (aqueous solution of NaCl brine) on a homogeneous sand column. Two differential pressure transducers are used to measure the pressure drop across each phase, and six ring electrodes are used to measure the electrical resistance across five segments of the sand column. The electrical resistances are converted to water saturations with the aid of the Archie Equation for resistivity index. Both k rw and k rg are regarded as power functions of water, Caw, and gas, Cag, capillary numbers, the exponents of which are estimated with non-linear fitting to the experimental datasets. An analogous power law is used to express water saturation as a function of Caw, and Cag. In agreement to earlier studies, it seems that the two-phase flow regime is dominated by connected pathway flow and disconnected ganglia dynamics for the wetting fluid (brine), and only disconnected ganglia dynamics for the non-wetting fluid (gas). The water saturation is insensitive to changes of water and gas capillary numbers. Each relative permeability is affected by both water and gas capillary numbers, with the water relative permeability being a strong function of water capillary number and gas relative permeability depending strongly on the gas capillary number. The slope of the water relative permeability curve for a gas/water system is much higher than that of an oil/water system, and the slope of the gas relative permeability is lower than that of an oil/water system.

Tsakiroglou, Christos D. - One of the best experts on this subject based on the ideXlab platform.

  • The correlation of the steady-state gas/water relative permeabilities of porous media with gas and water capillary numbers
    'EDP Sciences', 2019
    Co-Authors: Tsakiroglou, Christos D.
    Abstract:

    International audienceThe steady-state gas, krg, and water, krw, relative permeabilities are measured with experiments of the simultaneous flow, at varying flow rates, of nitrogen and brine (aqueous solution of NaCl brine) on a homogeneous sand column. Two differential pressure transducers are used to measure the pressure drop across each phase, and six ring electrodes are used to measure the electrical resistance across five segments of the sand column. The electrical resistances are converted to water saturations with the aid of the Archie Equation for resistivity index. Both krw and krg are regarded as power functions of water, Caw, and gas, Cag, capillary numbers, the exponents of which are estimated with non-linear fitting to the experimental datasets. An analogous power law is used to express water saturation as a function of Caw, and Cag. In agreement to earlier studies, it seems that the two-phase flow regime is dominated by connected pathway flow and disconnected ganglia dynamics for the wetting fluid (brine), and only disconnected ganglia dynamics for the non-wetting fluid (gas). The water saturation is insensitive to changes of water and gas capillary numbers. Each relative permeability is affected by both water and gas capillary numbers, with the water relative permeability being a strong function of water capillary number and gas relative permeability depending strongly on the gas capillary number. The slope of the water relative permeability curve for a gas/water system is much higher than that of an oil/water system, and the slope of the gas relative permeability is lower than that of an oil/water system

Vincent Mashaba - One of the best experts on this subject based on the ideXlab platform.

  • Calculation of water saturation in low resistivity gas reservoirs and pay-zones of the Cretaceous Grudja Formation, onshore Mozambique basin
    Marine and Petroleum Geology, 2015
    Co-Authors: Vincent Mashaba, Wladyslaw Altermann
    Abstract:

    Abstract The water saturation of a hydrocarbon bearing formation is usually calculated via the conductivity of the formation water, as defined by Archie, 1942. However, in some formations such conventionally calculated water saturation contradicts values calculated from the Nuclear Magnetic Resonance (NMR) tool and from the Drill Stem Test (DST). Here we discuss such a case of low resistivity pay zones in the J- and K-Reservoirs, of the Lower Grudja Formation of Maastrichtian age, onshore Mozambique basin, in which conventional log analysis contradicts water saturation calculated from the NMR and by the Drill Stem Test. For both, the J-Reservoir and K-Reservoir, the water saturation (Sw) was calculated using the Archie Equation and the Simandoux Equation, that accounts for clay bound water but not for silt, and the results were compared to NMR-calculated water saturation. A new algorithm that improves the accuracy of water saturation calculation was introduced. This new algorithm takes into account the clay- and silt-bound water within the overall reservoir resistivity. It is demonstrated that the clay- and silt-bound water must be included in water saturation calculations, where the formations are rich in silt and clay. The Simandoux Equation and the new algorithm yield significant improvement in water saturation results for the J- and K-Reservoirs, when compared to water saturation calculated using the Archie's Equation.

Dongming Liu - One of the best experts on this subject based on the ideXlab platform.

  • High-altitude well log evaluation of a permafrost gas hydrate reservoir in the Muli area of Qinghai, China.
    Scientific reports, 2018
    Co-Authors: Zhenzhou Lin, Heping Pan, Hui Fang, Gao Wenli, Dongming Liu
    Abstract:

    The Muli area is the only permafrost region on the Chinese mainland wherein gas hydrates have been discovered. The gas hydrates are present in the fractures and pore spaces of the host rocks with a lamellar or micro-disseminated structure. By combining conventional and image logs, we describe the thickness of the permafrost layer and the well log responses of the gas hydrate reservoir, and calculate the porosity and gas hydrate saturation. We then analyze the advantages and disadvantages of different logging methods for evaluating gas hydrate reservoirs. Our results indicate that (1) gas hydrates are present below the permafrost in the Muli area, (2) gas hydrates predominantly occur in rock fractures, (3) the apparent resistivity is sensitive to gas hydrates present in pore spaces, and both apparent resistivity and acoustic logs are sensitive to gas hydrates present in fractures, (4) a density log is more appropriate for calculating porosity, and (5) gas hydrate saturation can be effectively calculated by the Archie Equation, the modified Archie Equation, and the Indonesian Equation.