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Maheswar Ojha - One of the best experts on this subject based on the ideXlab platform.
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gas hydrates saturation using geostatistical inversion in a Fractured Reservoir in the krishna godavari basin offshore eastern india
Marine and Petroleum Geology, 2013Co-Authors: Xiujuan Wang, Kalachand Sain, N Satyavani, Jiliang Wang, Maheswar OjhaAbstract:A Reservoir of gas hydrates filling fractures was discovered in the Krishna-Godavari (KG) Basin during the Indian National Gas Hydrate Program (NGHP) Expedition 01 at site NGHP01-10. The existing methods for estimating gas hydrate saturation from seismic data rely on establishing an empirical relation between acoustic impedance and density porosity from well logs assuming isotropic pore-filling gas hydrate. This method, however, yields a misleading saturation for Fractured clay-dominated sediments. Here we present a methodology to estimate gas hydrate saturation from seismic data based on geostatistical inversion. It integrates the verticals detail of well log data with the lateral details from seismic data to produce highly detailed estimates of gas hydrate saturation. First, gas hydrate saturation is calculated from P-wave velocities assuming anisotropic distribution at the well site. Then, probability density functions (PDFs) between acoustic impedance and the calculated gas hydrate saturation at the well site are analyzed. A Markov Chain Monte Carlo method is employed to integrate well logs with the seismic data to produce acoustic impedance. Finally, crossplots and histograms at the well site are used to estimate gas hydrate saturations along the seismic line from inverted acoustic impedance. The spatial distribution of gas hydrate varies both laterally and vertically along the line with an average saturation of 22.5%. The estimate matches reasonably with the value at the wells. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
Timothy S Collett - One of the best experts on this subject based on the ideXlab platform.
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gas hydrate saturations estimated from Fractured Reservoir at site nghp 01 10 krishna godavari basin india
Journal of Geophysical Research, 2009Co-Authors: Timothy S CollettAbstract:[1] During the Indian National Gas Hydrate Program Expedition 01 (NGHP-01), one of the richest marine gas hydrate accumulations was discovered at Site NGHP-01-10 in the Krishna-Godavari Basin. The occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures. Assuming the resistivity of gas hydrate– bearing sediments is isotropic, the conventional Archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50% (as high as � 80%) of the pore space for the depth interval between � 25 and � 160 m below seafloor. On the other hand, gas hydrate saturations estimated from pressure cores from nearby wells were less than � 26% of the pore space. Although intrasite variability may contribute to the difference, the primary cause of the saturation difference is attributed to the anisotropic nature of the Reservoir due to gas hydrate in high-angle fractures. Archie’s law can be used to estimate gas hydrate saturations in anisotropic Reservoir, with additional information such as elastic velocities to constrain Archie cementation parameters m and the saturation exponent n. Theory indicates that m and n depend on the direction of the measurement relative to fracture orientation, as well as depending on gas hydrate saturation. By using higher values of m and n in the resistivity analysis for Fractured Reservoirs, the difference between saturation estimates is significantly reduced, although a sizable difference remains. To better understand the nature of Fractured Reservoirs, wireline P and S wave velocities were also incorporated into the analysis.
John Killough - One of the best experts on this subject based on the ideXlab platform.
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General Multi-Porosity simulation for Fractured Reservoir modeling
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Masoud Alfi, Cheng An, Yuhe Wang, John KilloughAbstract:Abstract In the area of Fractured Reservoir modeling, conventional Dual Porosity Models is challenged to flexibly simulate more than two porosity systems and it is also difficult to capture the transient fluid transfer between matrix and fracture. This work aims to solve those problems in Fractured Reservoir simulation. The newly introduced Multi-Porosity Model honors any number of porosity types with different properties, such as permeability, porosity and wettability thus achieving significant improvements over conventional Dual-Porosity Models. Arbitrary connections for intra-porosity flow and inter-porosity flow are incorporated into the design to allow for the convenient transformation between Multi-Porosity and Multi-Permeability formulations. The addition of a flexible subdivision in each porosity system has allowed us to characterize the transient flow for inter-porosity flow. Due to the low permeability in the matrix, transient flow between matrix and fracture dominates, and thus matrix spatial subdivision is necessary to accurately capture the dynamics. The formulation is designed to allow the proposed scheme to be generalized. To quantify the improvements available with the new formulation, several typical Multi-Porosity Models are compared with Fine-Grid Single-Porosity Models. Consistent results have been obtained with those similar cases from literature, and the robustness and efficiency of the model is validated. Besides, the extra matrix subdivision is proven to accurately capture the transient fluid transfer between matrix and fracture.
Anvarbek Meirmanov - One of the best experts on this subject based on the ideXlab platform.
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DOUBLE POROSITY MODELS FOR LIQUID FILTRATION IN INCOMPRESSIBLE POROELASTIC MEDIA
Mathematical Models and Methods in Applied Sciences, 2010Co-Authors: Anvarbek MeirmanovAbstract:Double porosity models for the liquid filtration in a naturally Fractured Reservoir is derived from the homogenization theory. The governing equations on the microscopic level consist of the stationary Stokes system for an incompressible viscous fluid, occupying a crack-pore space (liquid domain), and stationary Lame equations for an incompressible elastic solid skeleton, coupled with the corresponding boundary conditions on the common boundary "solid skeleton-liquid domain". We assume that the liquid domain is a union of two independent systems of cracks (fissures) and pores, and that the dimensionless size δ of pores depends on the dimensionless size e of cracks: δ = er with r > 1. The rigorous justification is fulfilled for homogenization procedure as the dimensionless size of the cracks tends to zero, while the solid body is geometrically periodic. As the result we derive the well-known Biot–Terzaghi system of liquid filtration in poroelastic media, which consists of the usual Darcy law for the liquid...
Xiujuan Wang - One of the best experts on this subject based on the ideXlab platform.
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gas hydrates saturation using geostatistical inversion in a Fractured Reservoir in the krishna godavari basin offshore eastern india
Marine and Petroleum Geology, 2013Co-Authors: Xiujuan Wang, Kalachand Sain, N Satyavani, Jiliang Wang, Maheswar OjhaAbstract:A Reservoir of gas hydrates filling fractures was discovered in the Krishna-Godavari (KG) Basin during the Indian National Gas Hydrate Program (NGHP) Expedition 01 at site NGHP01-10. The existing methods for estimating gas hydrate saturation from seismic data rely on establishing an empirical relation between acoustic impedance and density porosity from well logs assuming isotropic pore-filling gas hydrate. This method, however, yields a misleading saturation for Fractured clay-dominated sediments. Here we present a methodology to estimate gas hydrate saturation from seismic data based on geostatistical inversion. It integrates the verticals detail of well log data with the lateral details from seismic data to produce highly detailed estimates of gas hydrate saturation. First, gas hydrate saturation is calculated from P-wave velocities assuming anisotropic distribution at the well site. Then, probability density functions (PDFs) between acoustic impedance and the calculated gas hydrate saturation at the well site are analyzed. A Markov Chain Monte Carlo method is employed to integrate well logs with the seismic data to produce acoustic impedance. Finally, crossplots and histograms at the well site are used to estimate gas hydrate saturations along the seismic line from inverted acoustic impedance. The spatial distribution of gas hydrate varies both laterally and vertically along the line with an average saturation of 22.5%. The estimate matches reasonably with the value at the wells. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
