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Zhicheng Li - One of the best experts on this subject based on the ideXlab platform.
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controls on Reservoir Heterogeneity of tight sand oil Reservoirs in upper triassic yanchang formation in longdong area southwest ordos basin china implications for Reservoir quality prediction and oil accumulation
Marine and Petroleum Geology, 2016Co-Authors: Yong Zhou, Youliang Ji, Liming Xu, Yuqi Zhou, Zhicheng LiAbstract:Abstract Compared to conventional Reservoirs, pore structure and diagenetic alterations of unconventional tight sand oil Reservoirs are highly heterogeneous. The Upper Triassic Yanchang Formation is a major tight-oil-bearing formation in the Ordos Basin, providing an opportunity to study the factors that control Reservoir Heterogeneity and the Heterogeneity of oil accumulation in tight oil sandstones. The Chang 8 tight oil sandstone in the study area is comprised of fine-to medium-grained, moderately to well-sorted lithic arkose and feldspathic litharenite. The Reservoir quality is extremely heterogeneous due to large heterogeneities in the depositional facies, pore structures and diagenetic alterations. Small throat size is believed to be responsible for the ultra-low permeability in tight oil Reservoirs. Most Reservoirs with good Reservoir quality, larger pore-throat size, lower pore-throat radius ratio and well pore connectivity were deposited in high-energy environments, such as distributary channels and mouth bars. For a given depositional facies, Reservoir quality varies with the bedding structures. Massive- or parallel-bedded sandstones are more favorable for the development of porosity and permeability sweet zones for oil charging and accumulation than cross-bedded sandstones. Authigenic chlorite rim cementation and dissolution of unstable detrital grains are two major diagenetic processes that preserve porosity and permeability sweet zones in oil-bearing intervals. Nevertheless, chlorite rims cannot effectively preserve porosity-permeability when the chlorite content is greater than a threshold value of 7%, and compaction played a minor role in porosity destruction in the situation. Intensive cementation of pore-lining chlorites significantly reduces Reservoir permeability by obstructing the pore-throats and reducing their connectivity. Stratigraphically, sandstones within 1 m from adjacent sandstone-mudstone contacts are usually tightly cemented (carbonate cement > 10%) with low porosity and permeability (lower than 10% and 0.1 mD, respectively). The carbonate cement most likely originates from external sources, probably derived from the surrounding mudstone. Most late carbonate cements filled the previously dissolved intra-feldspar pores and the residual intergranular pores, and finally formed the tight Reservoirs. The petrophysical properties significantly control the fluid flow capability and the oil charging/accumulation capability of the Chang 8 tight sandstones. Oil layers usually have oil saturation greater than 40%. A pore-throat radius of less than 0.4 μm is not effective for producible oil to flow, and the cut off of porosity and permeability for the net pay are 7% and 0.1 mD, respectively.
Yang Qin - One of the best experts on this subject based on the ideXlab platform.
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origin of calcite cements and their impact on Reservoir Heterogeneity in the triassic yanchang formation ordos basin china a combined petrological and geochemical study
Marine and Petroleum Geology, 2020Co-Authors: Delu Xie, Suping Yao, Jian Cao, Yang QinAbstract:Abstract Calcite cement is a typical product of fluid–rock interaction in petroleum Reservoirs, and its migration has a major impact on Reservoir Heterogeneity. A case study of a closed diagenetic system was carried out on the Upper Triassic Yanchang Formation of Ordos Basin, China—the most successful exploration region for tight sandstone oil in China. The investigated sandstones are mainly lithic arkoses (Q31F42L27). Three occurrences of calcite cement are the most important diagenetic minerals affecting Reservoir quality: early calcite completely filling intergranular volumes; late calcite filling pores after chlorite coating, distributed in oil layers, or locally replacing feldspar; and crystal-stock calcite typically distributed in dry layers. δ13C values of the sandstones are in the range −9.69‰ to −2.05‰, indicating that calcite is derived mainly from thermodynamic decarboxylation of organic matter. Dark mudstone interbedded with sandstone and hydrocarbon emplacement are the two crucial sources of organic fluid, providing sufficient Ca2+, Mn2+, Fe2+, and Mg2+ for calcite precipitation through interaction with feldspar and other silicates, such as dissolution and replacement together with transformation of smectite to illite. Manganese was continuously enriched in calcite during burial diagenesis. Driven by compaction of interbedded mudstone and fluid overpressure, calcite migrated widely into calcite-cemented zones (CCZs) where fluid–rock interaction was strong, such as in the margins of sandstone bodies, intrastratal sandstones with original high-permeability zones, and thin sandstones, thereby forming an important organic CO2 sink. Potential high-quality Reservoirs are distributed mainly in the central part of the closed system, restricted by calcite-cemented zones, and are an exploration target. Our data suggest that frequently alternating sandstone and mudstone sequences comprise a complete organic CO2 source/sink system, controlling the migration of calcite cement in a closed diagenetic system and Reservoir Heterogeneity by fluid–rock interaction.
Emad A Alkhdheeawi - One of the best experts on this subject based on the ideXlab platform.
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effect of wettability Heterogeneity and Reservoir temperature on co2 storage efficiency in deep saline aquifers
International Journal of Greenhouse Gas Control, 2018Co-Authors: Ahmed Barifcani, Emad A Alkhdheeawi, Stephanie Vialle, Mohammad Sarmadivaleh, Stefan IglauerAbstract:Abstract Reservoir Heterogeneity at various length scales is a well-established fact. This includes Reservoir wettability − a key factor influencing CO2 geo-storage efficiency and containment security − which changes with depth, and is generally non-uniform due to different depositional environments and fluid flow paths over geological times. However, the effect of heterogeneous wettability distribution on CO2 storage efficiency is not understood. Moreover, there is a knowledge gap in terms of how temperature affects capillary and dissolution trapping, CO2 mobility and vertical CO2 migration distance, particularly when coupled with wettability Heterogeneity effects. Thus, in this work we studied the effect of wettability Heterogeneity and Reservoir temperature on the vertical CO2 plume migration, and capillary and dissolution trapping capacities. Our results clearly show that both wettability Heterogeneity and Reservoir temperature have a significant effect on vertical CO2 migration, and the associated capillary and dissolution trapping mechanisms: both heterogeneously distributed wettability and higher temperature significantly accelerated the vertical CO2 migration, CO2 mobility and solubility trapping, while it reduced residual trapping. We thus conclude that wettability Heterogeneity and Reservoir temperature are important factors in the context of CO2 geo-storage, and that heterogeneous wettability and higher Reservoir temperatures reduce storage capacity.
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impact of Reservoir wettability and Heterogeneity on co2 plume migration and trapping capacity
International Journal of Greenhouse Gas Control, 2017Co-Authors: Ahmed Barifcani, Emad A Alkhdheeawi, Stephanie Vialle, Mohammad Sarmadivaleh, Stefan IglauerAbstract:Abstract Reservoir wettability – the tendency of a rock surface to be in contact with one fluid more than other fluids – can vary substantially from strongly water-wet to strongly CO2-wet. However, the influence of such differences in wettability on the CO2 storage capacity has received little attention. Here, we studied the impact of Reservoir wettability on CO2 plume behaviour and residual and solubility trapping capacities. We also compare the case of a homogeneous distribution of permeability and porosity values within the Reservoir with that of a heterogeneous distribution. We found that CO2-wet Reservoirs have the highest CO2 vertical migration, while water-wet Reservoirs best retain CO2. In addition, less residual CO2 but more dissolved CO2 is obtained in a CO2-wet Reservoir. Furthermore, we demonstrate that Reservoir Heterogeneity reduces the vertical CO2 migration and induces significant horizontal migration, while lower residual and solubility storage capacities are achieved. We thus conclude that both Reservoir wettability and Heterogeneity significantly impact CO2 migration and trapping capacities and need to be incorporated into Reservoir simulations for accurate predictions of both CO2 plume behaviour and CO2 storage capacities. Overall, we conclude that strongly water-wet Reservoirs are preferable CO2 sinks.
Sanjay Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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Reservoir sensitivity analysis for Heterogeneity and anisotropy effects quantification through the cyclic co2 assisted gravity drainage eor process a case study from south rumaila oil field
Fuel, 2018Co-Authors: Watheq J Almudhafar, Dandina N Rao, Sanjay SrinivasanAbstract:Abstract The effects of Reservoir Heterogeneity and anisotropy were quantified through the cyclic CO2-Assisted Gravity Drainage (GAGD) process performance in a heterogeneous multi-layering sandstone Reservoir. First, an integrating workflow of multiple-point geostatistics (MPS) and Sequential Gaussian Simulation (SGSIM) was adopted for the lithological and petrophysical modeling to capture the fluvial depositional environment and preserve the Reservoir Heterogeneity, respectively. Next, sensitivity analysis was conducted through compositional Reservoir simulation and Design of Experiments (DoE) to eliminate the non-influencing petrophysical parameters on the GAGD process performance. Then, Heterogeneity and anisotropy effects were quantified with respect to Reservoir permeability and anisotropy ratio, respectively. The effects was attained by generating and incorporating multiple Reservoir stochastic images (realizations) that capture the entire geological uncertainty space into the Reservoir flow simulation. Based on the Reservoir flow responses, it was concluded that the impact of permeability anisotropy on the GAGD process is higher than that of Heterogeneity, because the main concept of GAGD process considers vertical fluid movements from the top-layer injection wells to the horizontal producers.
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effects of Reservoir Heterogeneity on scaling of effective mass transfer coefficient for solute transport
Journal of Contaminant Hydrology, 2016Co-Authors: Juliana Y Leung, Sanjay SrinivasanAbstract:Abstract Modeling transport process at large scale requires proper scale-up of subsurface Heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous Reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the Reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-Heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple Reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of Heterogeneity on the scaling of effective transport parameters. A key finding is that spatial Heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It reinforces the notion that the flow response is influenced by the higher-order statistical description of Heterogeneity. An important implication is that when scaling-up transport response from lab-scale results to the field scale, it is necessary to account for the scale-up of Heterogeneity. Since the characteristics of higher-order multivariate distributions and large-scale Heterogeneity are typically not captured in small-scale experiments, a Reservoir modeling framework that captures the uncertainty in Heterogeneity description should be adopted.
Yong Zhou - One of the best experts on this subject based on the ideXlab platform.
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controls on Reservoir Heterogeneity of tight sand oil Reservoirs in upper triassic yanchang formation in longdong area southwest ordos basin china implications for Reservoir quality prediction and oil accumulation
Marine and Petroleum Geology, 2016Co-Authors: Yong Zhou, Youliang Ji, Liming Xu, Yuqi Zhou, Zhicheng LiAbstract:Abstract Compared to conventional Reservoirs, pore structure and diagenetic alterations of unconventional tight sand oil Reservoirs are highly heterogeneous. The Upper Triassic Yanchang Formation is a major tight-oil-bearing formation in the Ordos Basin, providing an opportunity to study the factors that control Reservoir Heterogeneity and the Heterogeneity of oil accumulation in tight oil sandstones. The Chang 8 tight oil sandstone in the study area is comprised of fine-to medium-grained, moderately to well-sorted lithic arkose and feldspathic litharenite. The Reservoir quality is extremely heterogeneous due to large heterogeneities in the depositional facies, pore structures and diagenetic alterations. Small throat size is believed to be responsible for the ultra-low permeability in tight oil Reservoirs. Most Reservoirs with good Reservoir quality, larger pore-throat size, lower pore-throat radius ratio and well pore connectivity were deposited in high-energy environments, such as distributary channels and mouth bars. For a given depositional facies, Reservoir quality varies with the bedding structures. Massive- or parallel-bedded sandstones are more favorable for the development of porosity and permeability sweet zones for oil charging and accumulation than cross-bedded sandstones. Authigenic chlorite rim cementation and dissolution of unstable detrital grains are two major diagenetic processes that preserve porosity and permeability sweet zones in oil-bearing intervals. Nevertheless, chlorite rims cannot effectively preserve porosity-permeability when the chlorite content is greater than a threshold value of 7%, and compaction played a minor role in porosity destruction in the situation. Intensive cementation of pore-lining chlorites significantly reduces Reservoir permeability by obstructing the pore-throats and reducing their connectivity. Stratigraphically, sandstones within 1 m from adjacent sandstone-mudstone contacts are usually tightly cemented (carbonate cement > 10%) with low porosity and permeability (lower than 10% and 0.1 mD, respectively). The carbonate cement most likely originates from external sources, probably derived from the surrounding mudstone. Most late carbonate cements filled the previously dissolved intra-feldspar pores and the residual intergranular pores, and finally formed the tight Reservoirs. The petrophysical properties significantly control the fluid flow capability and the oil charging/accumulation capability of the Chang 8 tight sandstones. Oil layers usually have oil saturation greater than 40%. A pore-throat radius of less than 0.4 μm is not effective for producible oil to flow, and the cut off of porosity and permeability for the net pay are 7% and 0.1 mD, respectively.
