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O. O. Blake - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Effective Pressure on the Relationship Between Static and Dynamic Young’s Moduli and Poisson’s Ratio of Naparima Hill Formation Mudstones
Rock Mechanics and Rock Engineering, 2020Co-Authors: O. O. Blake, R. Ramsook, D. R. Faulkner, U. C. IyareAbstract:Static elastic properties, derived from stress–strain data, and dynamic elastic properties, derived from P- and S-wave velocities, are significantly different for rocks. Most rocks are deformed nearly statically (due to tectonic forces and reservoir compaction during production of the reservoir) but static measurements are not as readily available as dynamic measurements. Hence, empirical relationships between the static and dynamic elastic properties are needed to convert the dynamic elastic properties to static values. In this study, the static and dynamic Young’s moduli and Poisson’s ratio were measured simultaneously for dry and fluid-saturated mudstone samples. The samples were axially loaded only within the elastic region to determine the static elasticity. The samples were from four different lithofacies within the Naparima Hill Formation, Trinidad, West Indies. Experiments were carried out at Effective Pressures up to 130 MPa to determine if the relationship, if any, is influenced by Effective Pressure. The results show that the dynamic Young’s modulus is greater than the static Young’s moduli. Saturation of the samples causes a decrease in the Young’s modulus and an increase in Poisson’s ratio. Saturation also increases the difference between the static and dynamic Young’s moduli and Poisson’s ratio. A linear relationship with high correlation ( R ^2 greater than 0.9) was established between the static and dynamic Young’s moduli. The gradient of the linear relationship increases, while the intercept decreases, with increasing Effective Pressure and axial loading. No clear trend was observed between the static and dynamic Poisson’s ratio.
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The role of fractures, Effective Pressure and loading on the difference between the static and dynamic Poisson's ratio and Young's modulus of Westerly granite
International Journal of Rock Mechanics and Mining Sciences, 2019Co-Authors: O. O. Blake, Daniel R. Faulkner, D. TathamAbstract:Abstract Fracture in rock is a major factor that affects the rock's elastic properties. Elastic properties can be measured statically during slow loading of a specimen, or dynamically, where the elasticity can be calculated using elastic-wave velocity. However, differences exist between the static and dynamic elastic properties. In this study, the dynamic and static elastic properties were measured under varying Effective Pressures and differential loads for dry and water-saturated Westerly granite that was thermally treated to 250, 450, 650 and 850 °C. Increasing the temperature produces an increased fracture density that is isotropically distributed. Increased fracture density results in a reduction in the Young's modulus and an increase in the Poisson's ratio, in both the static and dynamic cases, and is very significant for rocks treated above 450 °C. The dynamic Young's modulus is larger than the static value and the difference between them increases when water saturated. Under dry conditions, the static Young's modulus shows good correlation with dynamic values regardless of fracture density, loading or Effective Pressure. The static and dynamic Poisson's ratio are close to each other under both dry and saturated conditions. However, deviation between the static and dynamic Poisson's ratio occurs when the fracture density is high, differential load is high and Effective Pressure is low.
Natalia Jasminska - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation and experimental analysis of acoustic wave influences on brake mean Effective Pressure in thrust ejector inlet pipe of combustion engine
International Journal of Vehicle Design, 2015Co-Authors: Michal Puskar, Tomas Brestovic, Natalia JasminskaAbstract:This paper is focused on a numerical simulation and experimental analysis of acoustic wave influences on brake mean Effective Pressure in a thrust–ejector inlet pipe of a piston combustion engine. The experiment is based on a real racing motorbike, which is driven by a piston combustion engine, equipped with a newly developed and patented thrust–ejector inlet pipe. This new inlet pipe is able to eliminate problems concerning an insufficient charging of cylinder with a fresh mixture. The engine sucks the air by overPressure, which is directly related to increased performance and torque. The first part of this paper presents the analytical relations describing acoustic waves in an inlet pipe. The next part contains a numerical simulation performed by software Ansys CFX in order to obtain a detailed description of flowing air, which passes through the ejector into the air box. The experimental measurements were realised using the data–recording system EW&C.
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Numerical simulation and experimental analysis of acoustic wave influences on brake mean Effective Pressure in thrust–ejector inlet pipe of combustion engine
International Journal of Vehicle Design, 2015Co-Authors: Michal Puskar, Tomas Brestovic, Natalia JasminskaAbstract:This paper is focused on a numerical simulation and experimental analysis of acoustic wave influences on brake mean Effective Pressure in a thrust–ejector inlet pipe of a piston combustion engine. The experiment is based on a real racing motorbike, which is driven by a piston combustion engine, equipped with a newly developed and patented thrust–ejector inlet pipe. This new inlet pipe is able to eliminate problems concerning an insufficient charging of cylinder with a fresh mixture. The engine sucks the air by overPressure, which is directly related to increased performance and torque. The first part of this paper presents the analytical relations describing acoustic waves in an inlet pipe. The next part contains a numerical simulation performed by software Ansys CFX in order to obtain a detailed description of flowing air, which passes through the ejector into the air box. The experimental measurements were realised using the data–recording system EW&C.
Wenlian Xiao - One of the best experts on this subject based on the ideXlab platform.
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Effect of clay minerals on the Effective Pressure law in clay-rich sandstones
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Wenlian Xiao, Jinzhou Zhao, Zheng Lingli, Zhao-peng ZhangAbstract:Abstract The relative sensitivity of permeability to pore fluid Pressure Pp and confining Pressure Pc of rocks can be expressed as the Effective Pressure coefficient nk. To investigate the effect of clay minerals on nk, permeability data were measured in clay-rich sandstones under conditions of lowering Pp at different constant-confining Pressures, and the Effective Pressure coefficients were subsequently calculated using a method based on our observation that the Effective Pressure law was linear. The values of nk in I/S-sandstones and chlorite-sandstone agreed with the clay shell model, while the values of nk in kaolinite-sandstones were consistent with the clay particle model. However, the nk values of our kaolinite-sandstones were less than 1.0, which is different from previous observations showing nk greater than 1.0. The nk value of our I/S-sandstone saturated with formation water was greater than 1.0, consistent with the previous results, but the nk value of our I/S-sandstone saturated with dried nitrogen was lower than 1.0. Thus, the coefficient nk was affected by the type of clay mineral, the preparation of the samples, and the type of the pore fluid.
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The Effective Pressure law for permeability of clay-rich sandstones
Petroleum Science, 2011Co-Authors: Jinzhou Zhao, Wenlian Xiao, Zuping Xiang, Jun WangAbstract:To study the relative sensitivity of permeability to pore Pressure Pp and confining Pressure Pc for clay-rich rocks, permeability measurements were performed on samples of four clay-rich sandstones. A new method (hereafter denoted the “slide method”) was developed and used for analyzing the permeability data obtained. The Effective Pressure coefficients for permeability n k were calculated. The values of n k were found to be greater than 1.0 and insensitive to changes in Pressure. These results confirmed observations previously made on clay-rich rocks. Also, the coefficients n k obtained had different characteristics for different samples because of differences in the types of clay they contained. The Effective Pressure law (σeff=Pc−n k Pp) determined using the slide method gave better results about k(σeff) than classic Terzaghi’s law (σeff=Pc−Pp).
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Effective Pressure law for permeability of E‐bei sandstones
Journal of Geophysical Research, 2009Co-Authors: Yves Bernabé, Wenlian Xiao, Z.-y. Chen, Z.-q. LiuAbstract:[1] Laboratory experiments were conducted to determine the Effective Pressure law for permeability of tight sandstone rocks from the E-bei gas reservoir, China. The permeability k of five core samples was measured while cycling the confining Pressure pc and fluid Pressure pf. The permeability data were analyzed using the response-surface method, a statistical model-building approach yielding a representation of k in (pc, pf) space that can be used to determine the Effective Pressure law, i.e., peff = pc − κpf. The results show that the coefficient κ of the Effective Pressure law for permeability varies with confining Pressure and fluid Pressure as well as with the loading or unloading cycles (i.e., hysteresis effect). Moreover, κ took very small values in some of the samples, even possibly lower than the value of porosity, in contradiction with a well-accepted theoretical model. We also reanalyzed a previously published permeability data set on fissured crystalline rocks and found again that the κ varies with pc but did not observe κ values lower than 0.4, a value much larger than porosity. Analysis of the dependence of permeability on Effective Pressure suggests that the occurrence of low κ values may be linked to the high-Pressure sensitivity of E-bei sandstones.
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Effective Pressure law for permeability of e bei sandstones
Journal of Geophysical Research, 2009Co-Authors: Yves Bernabé, Wenlian Xiao, Z.-y. Chen, Z.-q. LiuAbstract:[1] Laboratory experiments were conducted to determine the Effective Pressure law for permeability of tight sandstone rocks from the E-bei gas reservoir, China. The permeability k of five core samples was measured while cycling the confining Pressure pc and fluid Pressure pf. The permeability data were analyzed using the response-surface method, a statistical model-building approach yielding a representation of k in (pc, pf) space that can be used to determine the Effective Pressure law, i.e., peff = pc − κpf. The results show that the coefficient κ of the Effective Pressure law for permeability varies with confining Pressure and fluid Pressure as well as with the loading or unloading cycles (i.e., hysteresis effect). Moreover, κ took very small values in some of the samples, even possibly lower than the value of porosity, in contradiction with a well-accepted theoretical model. We also reanalyzed a previously published permeability data set on fissured crystalline rocks and found again that the κ varies with pc but did not observe κ values lower than 0.4, a value much larger than porosity. Analysis of the dependence of permeability on Effective Pressure suggests that the occurrence of low κ values may be linked to the high-Pressure sensitivity of E-bei sandstones.
U. C. Iyare - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Effective Pressure on the Relationship Between Static and Dynamic Young’s Moduli and Poisson’s Ratio of Naparima Hill Formation Mudstones
Rock Mechanics and Rock Engineering, 2020Co-Authors: O. O. Blake, R. Ramsook, D. R. Faulkner, U. C. IyareAbstract:Static elastic properties, derived from stress–strain data, and dynamic elastic properties, derived from P- and S-wave velocities, are significantly different for rocks. Most rocks are deformed nearly statically (due to tectonic forces and reservoir compaction during production of the reservoir) but static measurements are not as readily available as dynamic measurements. Hence, empirical relationships between the static and dynamic elastic properties are needed to convert the dynamic elastic properties to static values. In this study, the static and dynamic Young’s moduli and Poisson’s ratio were measured simultaneously for dry and fluid-saturated mudstone samples. The samples were axially loaded only within the elastic region to determine the static elasticity. The samples were from four different lithofacies within the Naparima Hill Formation, Trinidad, West Indies. Experiments were carried out at Effective Pressures up to 130 MPa to determine if the relationship, if any, is influenced by Effective Pressure. The results show that the dynamic Young’s modulus is greater than the static Young’s moduli. Saturation of the samples causes a decrease in the Young’s modulus and an increase in Poisson’s ratio. Saturation also increases the difference between the static and dynamic Young’s moduli and Poisson’s ratio. A linear relationship with high correlation ( R ^2 greater than 0.9) was established between the static and dynamic Young’s moduli. The gradient of the linear relationship increases, while the intercept decreases, with increasing Effective Pressure and axial loading. No clear trend was observed between the static and dynamic Poisson’s ratio.
Jinzhou Zhao - One of the best experts on this subject based on the ideXlab platform.
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Effective Pressure law for the intrinsic formation factor in low permeability sandstones
Journal of Geophysical Research: Solid Earth, 2017Co-Authors: Meng Chen, Yves Bernabé, Jinzhou Zhao, L. H. Zhang, Z. Y. Zhang, Y. B. Tang, W. L. XiaoAbstract:Summary The Effective Pressure law for the intrinsic formation factor of low permeability sandstones from the Ordos Basin (northwest of China) was studied experimentally by measuring the electrical resistivity of brine saturated rock samples while cycling the pore and confining Pressures, pp and pc. We used a 100,000 ppm NaCl solution so that the results could be directly interpreted in terms of the intrinsic formation factor F. The Response Surface method was used to construct a quadratic function of pp and pc fitting the experimental data, from which the coefficient α of the Effective Pressure law, peff=pc – αpp, was determined. We found that the coefficient α generally had low values, mainly from 0.2 to 0.4, thus contradicting the theoretical prediction that α should be equal to 1 for scale-invariant properties, such as F, in linear elastic materials having a homogeneous solid matrix. Since the two underlying assumptions, linear elasticity and homogeneity of the solid matrix, are likely violated in reservoir rocks, we tried to assess their effects on α using simple analytical models, based on idealized geometries of the pore and solid phases. Analysis of these models suggests that non-linear elasticity associated with the formation of solid-solid contacts in the compressed rocks (e.g., during closure of rough cracks or crack-like pores along the grain boundaries), may be more Effective in producing the low α values observed than inhomogeneity of the solid matrix.
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Effect of clay minerals on the Effective Pressure law in clay-rich sandstones
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Wenlian Xiao, Jinzhou Zhao, Zheng Lingli, Zhao-peng ZhangAbstract:Abstract The relative sensitivity of permeability to pore fluid Pressure Pp and confining Pressure Pc of rocks can be expressed as the Effective Pressure coefficient nk. To investigate the effect of clay minerals on nk, permeability data were measured in clay-rich sandstones under conditions of lowering Pp at different constant-confining Pressures, and the Effective Pressure coefficients were subsequently calculated using a method based on our observation that the Effective Pressure law was linear. The values of nk in I/S-sandstones and chlorite-sandstone agreed with the clay shell model, while the values of nk in kaolinite-sandstones were consistent with the clay particle model. However, the nk values of our kaolinite-sandstones were less than 1.0, which is different from previous observations showing nk greater than 1.0. The nk value of our I/S-sandstone saturated with formation water was greater than 1.0, consistent with the previous results, but the nk value of our I/S-sandstone saturated with dried nitrogen was lower than 1.0. Thus, the coefficient nk was affected by the type of clay mineral, the preparation of the samples, and the type of the pore fluid.
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Nonlinear Effective Pressure law for permeability
Journal of Geophysical Research, 2014Co-Authors: M Li, Yves Bernabé, W. L. Xiao, Jinzhou ZhaoAbstract:The permeability k of porous rocks is known to vary with confining Pressure pc and pore fluid Pressure pf. But it is, in principle, possible to replace the two-variable function k(pf, pc) by a function k(peff) of a single variable, peff(pf, pc), called the Effective Pressure. Our goal in this paper is to establish an experimental method for determining a possibly nonlinear, Effective Pressure law (EPL) for permeability, i.e., find the function κs(pf, pc) such that the Effective Pressure is given by peff = pc − κs(pf, pc) pf. We applied this method to a set of 26 sandstone cores from various hydrocarbon reservoirs in China. We found that κs greatly varied, from sample to sample, in magnitude and range, sometimes even reaching theoretically prohibited values (i.e., greater than 1 or lower than porosity). One interesting feature of κs(pf, pc) is that it could be approximately described in all rocks but one as a decreasing function κs(pc − pf) of Terzaghi's differential Pressure. We also investigated the dependence of permeability on peff for each of our samples. Three models from the literature, i.e., exponential (E), power law (P), and the Walsh model (W), were tested. The (W) model was more likely to fit the experimental data of cores with a high Pressure dependence of permeability whereas (E) occurred more frequently in low-Pressure-sensitive rocks. Finally, we made various types of two- and three-dimensional microstructural observations that generally supported the trend mentioned above.
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The Effective Pressure law for permeability of clay-rich sandstones
Petroleum Science, 2011Co-Authors: Jinzhou Zhao, Wenlian Xiao, Zuping Xiang, Jun WangAbstract:To study the relative sensitivity of permeability to pore Pressure Pp and confining Pressure Pc for clay-rich rocks, permeability measurements were performed on samples of four clay-rich sandstones. A new method (hereafter denoted the “slide method”) was developed and used for analyzing the permeability data obtained. The Effective Pressure coefficients for permeability n k were calculated. The values of n k were found to be greater than 1.0 and insensitive to changes in Pressure. These results confirmed observations previously made on clay-rich rocks. Also, the coefficients n k obtained had different characteristics for different samples because of differences in the types of clay they contained. The Effective Pressure law (σeff=Pc−n k Pp) determined using the slide method gave better results about k(σeff) than classic Terzaghi’s law (σeff=Pc−Pp).
