Academic literature on the topic 'Relative magnetic permeability'

The performance of induction coil magnetic sensors , which usually have large dimensions and heavy weights, is mainly decided by apparent permeability of the core. But flux concentrator is a effective equipment to improve apparent permeability of the core, which will hardly increase dimensions and weights of magnetic sensors. Firstly, mathematical equations of apparent permeability are explained and influencing factors are analysed. Then influencing degrees of different parameters of the flux concentrator are simulated by Maxwell 2D/3D. The results are shown as follows. (a) The larger diameter and thickness of the flux concentrator, the better is the effect of magnetic concentration. (b) The less the gap between core and concentrator, the better is the effect of magnetic concentration. (c) The larger relative permeability of the flux concentrator, the effect of magnetic concentration is unconspicuous for the material whose relative permeabilityis larger than ten thousands.

The magnetic permeability of magnetorheological elastomers must be known for their long-term use in the actual engineering systems. In this article, the magnetic permeability of both isotropic and anisotropic magnetorheological elastomers has been determined using a new method. The magnetic induction was measured and a closed magnetic circuit analysis was carried out to obtain the magnetic permeability of magnetorheological elastomers for both isotropic and anisotropic magnetorheological elastomers with 10%–50% volume concentration of carbonyl iron particles. The magnetic permeability was increased with increasing particle concentration for both isotropic and anisotropic magnetorheological elastomers as we could expect. The isotropic permeability is always lower than the anisotropic permeability. The maximum relative permeability value of 6.6 was obtained for 50% particle volume concentration. The experimental results also show a good agreement with theoretical predictions and previous investigations.

Soft magnetic moldable composites (SM2Cs) would be ideally suited for the integration of magnetic components in power electronic converters because they can be formed into magnetic cores by low-temperature and pressure-less processing. However, most SM2Cs have low relative magnetic permeability, typically less than 30, and high core-loss densities at switching frequencies over 1 MHz. To improve their magnetic properties, we combine powders of Permalloy and a NiZn ferrite with an acrylic polymer to formulate a paste of SM2C. The paste can be molded and then cured below 200 °C without pressure to form cores with a relative permeability over 35 and a core-loss density at 1 MHz, 30% lower than those of commercial cores. The ease of its processing and high-performance properties makes the SM2C a good candidate material for the integration of power magnetics.

The inverse magnetostrictive effect provides a chance to detect the stress by measuring some magnetic parameters. So it is important to learn the effect of stress on some magnetic parameters. A measuring system to measure magnetic permeability and magnetic loss and a device to load uniaxial tension and pressure stress were developed. The result shows that magnetic permeability and magnetic loss increase with uniaxial tension stress increase and decreases with uniaxial pressure stress increase. It is also concluded that the relative change of magnetic permeability and magnetic loss decrease with increase of the included angle between the directions of the stress and magnetic field. These results suggest that magnetic permeability and magnetic loss can be further used to evaluate the stress in low-carbon steel.

This research is about the special theory of relativity on electric permittivity and magnetic permeability of electromagnetic wave. For this, Four Maxwell's electromagnetic equations play an important role. James Clerk Maxwell suggested that the light travel as electromagnetic wave which require no material medium for propagation. The speed of light (C) in free space is always constant and is independent of the speed of source or observer or the relative motion of the inertial system and has velocity 'C' given by . So velocity of electromagnetic waves depend on obsolute magnetic permeability and obsolute electric permittivity of free space. These two physical quantities rely on relative motion of inertial system. So are not obsolute quantity but are dependent upon the relative motion between the observer and the phenomenon observed. Electric and magnetic field of a charge rely upon the value of obsolute electric permittivity of medium. Concisely, are variant quantity. Consequently electric and magnetic field get relative for electromagnetic wave. That is electric and magnetic field depend on relative motion of inertial system for electromagnetic waves.

Исследуется зависимость эффективной площади рассеяния (ЭПР) от относительной магнитной проницаемости материала, из которого изготавливается структура. В качестве тела моделирования был выбран шар, который изготовлен из диэлектрического материала, у которого возможно выполнять изменение относительной магнитной проницаемости. По полученным результатам моделирования построены графики зависимости максимального значения моностатической ЭПР от частоты, а также от относительной магнитной проницаемости среды. Было показано, что с увеличением относительной магнитной проницаемости материала изготовления происходит увеличение значения ЭПР объекта, а также обнаружена зависимость эффективной площади рассеяния от соотношения размеров шара и длиной волны, так при превышении порогового значения, после которого шар становится крупным объектом, ЭПР резко возрастает. По результатам исследования был построен график зависимости эффективной площади рассеяния шара от относительной магнитной проницаемости материала изготовления. Доказана возможность применения материала с частотозависимой относительной магнитной проницаемостью в качестве стелс-покрытия. В статье содержится исследуемая модель, графики полученных результатов, по которым можно легко определить зависимость ЭПР от частоты и от относительной магнитной проницаемости материала изготовления The article investigates the dependence of the effective scattering area (ESA) on the relative magnetic permeability of the material from which the structure is made. We chose a sphere as the modeling body, which is made of a dielectric material, in which it is possible to change the relative magnetic permeability. Based on the obtained simulation results, graphs of the dependence of the maximum value of monostatic ESA on frequency, as well as on the relative magnetic permeability of the medium, were constructed. It was shown that with an increase in the relative magnetic permeability of the material of manufacture, an increase in the value of the ESA of the object occurs, and the dependence of the effective scattering area on the ratio of the size of the ball and the wavelength was found, so when the threshold value is exceeded, after which the ball becomes a large object, ESA rises sharply. Based on the results of the study, a graph of the dependence of the effective scattering area of the sphere on the relative magnetic permeability of the material of manufacture was built. The possibility of using a material with a frequency-dependent relative magnetic permeability as a stealth coating was proven. The article contains the investigated model, graphs of the results obtained, by which it is easy to determine the dependence of the ESA on the frequency and on the relative magnetic permeability of the material of manufacture

Paper studies the problems about experimental determining magnetic parameters of nonuniform granular magnetics. It has been noted that the existing shortage of direct and (or) indirect experimental data on the magnetic properties of granular ferromagnetic specimens with different values of a relative length, in particular, has a negative impact on the validity of the requirements and decisions to create and ensure the performance of relevant functional elements, movable operating elements of various equipments and devices. By the example of cylindrical specimens of balls with the range of relative length 1–16 within the framework of effective medium macromodel the dependences of induction, magnetic permeability, susceptibility, magnetization and field intensity have been obtained. It has been shown that in the range of field intensity 9–47 kA/m values of induction and magnetization of investigating specimens increase, that indicates the absence of magnetic saturation of such granular (as opposed to solid) magnetics. And this is the case at almost stable values of magnetic susceptibility and permeability. Obtained results are useful in designing movable operating elements of various equipments and devices.

The flow characteristics during decomposition of hydrate-bearing sediments are the most critical parameters for the gas recovery potential from natural gas hydrate reservoirs. The absolute and relative permeability and the flow field distribution during the decomposition process of hydrate-bearing porous media synthetically created by glass beads are in-situ measured by using magnetic resonance imaging. The absolute permeability value increased slowly, then became stable after the decomposition amount was 50%. The relative permeability change curve is a typical X-shaped cross curve. As the hydrate decomposed, the relative permeability values of the two phases increased, the range of the two-phase co-infiltration zone increased with the increase of relative permeability at the endpoint, and the coexistence water saturation decreased. At the beginning of the decomposition, (hydrate content 100% to 70%), the relative permeability of methane and water rose rapidly from 22% to 51% and from 58% to 70%, respectively. When the amount of the remaining hydrate was less than 50%, the relative permeability curve of the hydrate-bearing glass beads almost kept unchanged. During the hydrate decomposition process, the velocity distribution was very uneven and coincided with the porous media structure.

We note that for a wide range of porous, especially granular, ferromagnetics used as matrices of magnetic filter-separators, there is still an issue of defining their demagnetizing factor N which has a dramatic effect on the values of average magnetic permeability of these operating units of filter-separators. The work aims at filling the existent gaps in the issue, we supply N values depending on the relative size of such magnets as well as a respective generalizing phenomenological dependence which is characterized by an exponential realtion between the demagnetizing factor and relative size radical. The established relation allows obtaining real values of magnetic permeability of a short filter matrix thus providing an unbiased comparative estimate of its technological workability.

In this study a hybrid Pore Network (PN) model that simulates two-phase (water-oil) drainage and imbibition mechanisms is developed. The developed model produces Nuclear Magnetic Resonance (NMR) T2 relaxation times using correlations available in the literature. The developed PN was calibrated using experimental relative permeability data obtained for Berea Sandstone, Kuzey Marmara Limestone, Yenikö
y Dolostone and Dolomitic Limestone core plugs. Pore network body and throat parameters were obtained from serial computerized tomography scans and thin section images. It was observed that pore body and throat sizes were not statistically correlated. It was also observed that the developed PN model can be used to model different displacement mechanisms. By using the synthetic data obtained from PN model, an Artificial Neural Network (ANN) model was developed and tested. It has been observed that the developed ANN tool can be used to estimate oil &ndash
water relative permeability data very well (with less than 0.05 mean square error) given a T2 signal. It was finally concluded that the developed tools can be used to obtain multiphase flow functions directly from an NMR well log such as Combinable Magnetic Resonance (CMR).

У дисертаційній роботі представлені науково-технічні результати дослідження електромагнітного багатопараметрового перетворювача для визначення параметрів циліндричних металевих виробів, принцип роботи якого ґрунтується на виділенні амплітуди та фази просторових гармонік неоднорідного магнітного поля, представленого у вигляді ряду Фур'є. Об'єкт дослідження достатньо повно описаний в науковій літературі. Показано, що подальше збільшення інформаційних параметрів, які контролюються одним перетворювачем може здійснюватися декількома шляхами. Наприклад, використання для живлення перетворювача струмом різних частот з подальшою фільтрацією і виділенням амплітуди і фази на кожній частоті. Така реалізація багатопараметрових датчиків досить складна і не завжди відображає справжню картину процесів, що відбуваються в об'єкті контролю через різну глибину проникнення поля (скін-ефект). Показано, що застосування результатів дослідження дає можливість отримати більш повну інформацію про об'єкт контролю, яка не могла бути отримана при використанні традиційних методів. Тому, застосування розробленого методу, є перспективним. В роботі розроблена фізико-математична модель електромагнітного перетворювача з неоднорідним розподілом електромагнітного поля для провідника зі струмом, розташованого уздовж бічної поверхні циліндричного виробу на деякій відстані d від центра металевого циліндра радіуса a. Вирішена просторова задача розподілу змінного в часі магнітного поля і отримані вирази, за якими можна обчислити функції для будь-якої просторової гармоніки, за якими можна скласти картину розподілу поля в будь-який області (всередині виробу, між виробом і провідником зі струмом, а також поза цим провідником). Отримано математичні вирази для визначення напруженості магнітного поля для r-ї і φ-ї складової, створюваного струмом одного провідника (або полюса з кінцевими кутовими розмірами). Проведено облік товщини стрічки полюса з сумарним струмом, який призводить до заміни в формулах для напруженості поля значення r на деякий ефективний радіус. Отримано математичні вирази для амплітуди і фази n-ї просторової гармоніки сигналу перетворювача, що наводиться в вимірювальних обмотках, розташованих уздовж поверхні циліндричного об'єкту контролю з кутовою координатою φ на окружності радіуса d. Для підтвердження адекватності запропонованої моделі перетворювача проведені експерименти, які показали відмінність між розрахунковими і експериментально отриманими значеннями ЕРС вихідного сигналу перетворювача. Так, наприклад, для вимірювальних обмоток, з кутовими координатами φ = 0° і φ = 180° розбіжність значень напруг склала не більше 5%, а для обмоток з розташуванням по φ = 30°, 60°, 300° і 330° розбіжність склала не більше 10%. Запропоновано також прийоми і способи виділення необхідних просторових гармонік і приглушення гармонік з високими номерами. Останнє дозволяє знизити вплив вищих просторових гармонік до 1%. Для виключення з картини просторового розподілу поля парних або непарних гармонік запропоновано використовувати систему провідників з однаковими і протилежними напрямками струмів в них. Отримано універсальні функції перетворення для амплітуди і фази n-ї складової гармоніки для перетворювача. Розроблено метод спільного контролю електричних (σ), магнітних (μr) і геометричних (а) параметрів циліндричних виробів, на основі перетворювача з одним намагнічувальним полюсом при використанні 1-ї і 2-ї просторових гармонік, який дозволяє однозначно вирішувати задачу багатопараметрового контролю для широкого сортименту виробів, різних конструкцій і режимів роботи перетворювачів. Розроблено метод на основі електромагнітного перетворювача з двома намагнічувальними полюсами і різним напрямком струму. Отримано універсальні функції перетворення з використанням 1-ї і 3-ї просторових гармонік, а також запропонований алгоритм реалізації багатопараметрового контролю параметрів циліндричних виробів. Визначено чутливості методу і знайдено раціональні режими роботи перетворювача. Виконано розрахунок і показано вплив вищих гармонік поля на вихідні сигнали перетворювача. Так, наприклад, для перетворювача з одним збуджувальним провідником, відкидання 3-ї гармоніки призведе до похибки розрахунку результуючої ЕРС, яка дорівнює 5%, а для перетворювача з двома збуджувальними провідниками, при відкиданні 5-ї гармоніки, становить 1,5%. Розроблено макет лабораторної установки з електромагнітним перетворювачем з просторово-періодичною структурою поля і проведені експериментальні дослідження по визначенню μr σ, і а з імітаційними зразками різного сортаменту для підтвердження адекватності розробленого методу. Наведена конструкція електромагнітного перетворювача з двома збуджувальними полюсами і різним напрямком намагнічувального струму з використанням амплітуди 1-ї і 3-ї просторових гармонік і фази 1-ї гармоніки. Оскільки безпосередньо оцінити похибки контролю μr, σ і а для розробленого багатопараметрового перетворювача досить складно, в роботі проведено вимірювання цих же параметрів контрольними методами. Так для визначення а досліджуваного зразка використовувався мікрометр з діапазоном вимірювання діаметра (50 ± 0,01) мм, для визначення σ циліндричного зразка використовувався контактний електричний метод на базі потенціометра постійного струму Р363-3, з класом точності 0,005, а для визначення μr використовувався метод амперметра - вольтметра для кільцевого зразка. Показано, що застосування розробленого перетворювача дозволяє отримувати найбільш повну інформацію про стан повітряних ліній електропередач, тобто визначати μr, σ, і a циліндричних дротів, а також корельованих з ними механічним навантаженням, температурою, величиною струму, що протікає в лінії та визначення питомих електричних втрат при діагностиці стану повітряних ліній електропередач, що підтверджується актом впровадження від 18.12.2015р (договір № 377551 від 27.07.2015р між НТУ «ХПІ» та ПАТ «Укргідропроект» м. Харків).
The dissertation presents the scientific and technical results of the study of the electromagnetic multi-parameter transducer for the cylindrical metal products parameters determining, which principle is based on the allocation of the amplitude and phase of the spatial harmonics of a nonuniform magnetic field presented in the form of a Fourier series. The object of the study is in the full extent described in the scientific literature. It is shown that further increase of information parameters controlled by one transducer can be carried out in several ways. For example, the use of different frequency to power the transducers, signal filtering and separation of amplitude and phase at each frequency. Such implementation of multiparameter sensors is quite complicated and does not always give the true picture of the processes taking place in the controlled object due to the different depth of field penetration (skin effect). It has been shown that the application of the study results provides an opportunity to obtain more information about the studied object that could not be obtained by using traditional methods. Therefore, the application of the developed method is promising. The physic-mathematical model of an electromagnetic transducer with non-uniform distribution of an electromagnetic field for a conductor with a current located along the lateral surface of a cylindrical product at a distance d from the center of a metallic cylinder of radius a. The spatial problem of the distribution of a magnetic field variable in time is solved and expressions allowing calculating the functions for any spatial harmonic are obtained and it is possible to make a picture of the distribution of the field in any area (inside the product, between the product and conductor with current, as well as beyond this conductor). Mathematical expressions are obtained to determine the intensity of the magnetic field for r-th and φ-th components, generated by the current of one conductor (or pole with finite angular dimensions). The thickness of the pole with a total current is taken into account, which leads to the replacement of r quantity in the formulas for field strength by effective radius. Mathematical expressions are obtained to determine amplitude and phase of transducer’s signal n-th spatial harmonics, which are generated in the measuring windings located along the surface of the cylindrical object with the angular coordinate φ on a circle of radius d. Experiments have been carried out to confirm the adequacy of the transducer’ proposed model, which showed the difference between the calculated and experimentally obtained values of the EMF of the transducer’ output signal. For instance, for measuring windings with angular coordinates φ = 0° і φ = 180° difference of voltage values is less than 5% and for measuring windings with angular coordinates φ = 30°, 60°, 300° і 330° difference is less than 10%. Methods and algorithms of allocating the necessary spatial harmonics and eliminating harmonics with high numbers are offered also. The latter allows us to reduce the influence of the higher spatial harmonics down to 1%. To exclude from the spatial distribution of the field odd or even harmonics it is suggested to use a system of conductors with the same and opposite directions of currents in them. The universal transformation functions for the amplitude and phase of the n-th harmonic component for the transducer are obtained. Method is developed for simultaneous testing electrical (σ), magnet (μr) and geometrical (а) parameters of cylindrical objects, by the use of transducer with on magnetizing pole considering 1-st and 2-nd spatial harmonics, which allows unambiguously solve the task of multi-parameter testing for a wide variety of products, various designs and modes of operation of transducers. The method based on the electromagnetic transducer with two magnetized poles and a different direction of current is developed. The universal functions of conversion with use of 1-st and 3-rd spatial harmonics are obtained, also the algorithm of realization of cylindrical wares’ parameters multi-parameter control is offered. The sensitivity of the method is determined and rational modes of transducer operation are found. The calculation is performed and the effect of the higher harmonics of the field on the output signals of the transducer is shown. For example, for a transducer with one excitation wire, the rejection of the 3-rd harmonic will result in an error of the resulting EMF calculation equal to 5%, and for a transducer with two excitatory wires, when the 5-th harmonic is rejected, it is 1.5%. A layout of a laboratory unit with an electromagnetic transducer with a spatial-periodic field structure was developed and experimental studies were carried out to determine μr σ, and а with simulation samples of different sorts to confirm the adequacy of the developed method. The construction of an electromagnetic transducer with two excitation poles and a different direction of the magnetizing current with the use of the amplitude of the 1-st and 3-rd spatial harmonics and the 1-st harmonic phase is presented. As soon as direct estimation of error of testing μr, σ and а for the developed multi-parameter transducer is quite complicated, in the work the measurements of these parameters were carried out by control methods. So, to estimate а of the studied sample micrometer with a diameter measuring range (50 ± 0,01) mm was used, to estimate σ of a cylindrical sample, a contact electric method was used based on the potentiometer of direct current Р363-3 (R363-3), having accuracy class of 0,005, to estimate μr the method of an ammeter – voltmeter for a ring sample was used. It is shown that implementation of the developed transducer allows to receive the most complete information about the condition of electric power lines, that is to define μr, σ, and a of cylindrical wires, as well as the mechanical load, temperature, magnitude of the current flowing in the line correlated with them and the determination of specific electrical losses during the diagnosis of the state of electric power lines, as evidenced by the implementation act dated 18.12.2015 (agreement № 377551 dated 27.07.2015 between NTU “KhPI” and PJSC “Ukrhydroproekt” city of Kharkiv).

Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) зі спеціальності 05.11.13 – прилади і методи контролю та визначення складу речовин. Національний технічний університет "Харківський політехнічний інститут", Харків, 2019. В роботі розроблена фізико-математична модель електромагнітного перетворювача з неоднорідним розподілом електромагнітного поля провідника зі струмом, розташованого уздовж бічної поверхні циліндричного виробу на деякій відстані d від центра металевого циліндра радіуса a. Отримано математичні вирази для визначення напруженості магнітного поля для r-ї і φ-ї складової, створюваного струмом одного провідника або полюса. Проведено облік товщини стрічки полюса, який призводить до заміни в формулах для напруженості поля значення r на деякий ефективний радіус. Отримано математичні вирази для амплітуди і фази n-ї просторової гармоніки сигналу перетворювача, що наводиться в вимірювальних обмотках, розташованих уздовж поверхні циліндричного об'єкту контролю з кутовою координатою φ по колу радіуса d. Для підтвердження адекватності запропонованої моделі перетворювача проведені експерименти, які показали хороший збіг між розрахунковими і експериментальними значеннями ЕРС сигналу перетворювача. Так, наприклад, для вимірювальних обмоток, з кутовими координатами φ = 0° і φ = 180° розбіжність значень напруг склала не більше 5%, а для обмоток з розташуванням по φ = 30°, 60°, 300° і 330° розбіжність склала не більше 10%. Розроблено метод на основі електромагнітного перетворювача з двома полюсами і різним напрямком струму. Отримано універсальні функції перетворення з використанням 1-ї і 3-ї просторових гармонік, а також запропонований алгоритм реалізації багатопараметрового контролю параметрів циліндричних виробів.
Dissertation for the degree of candidate of technical sciences (doctor of philosophy) in specialty 05.11.13 – instruments and methods of substance composition control and determination. National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2019. The physic-mathematical model of an electromagnetic transducer with non-uniform distribution of an electromagnetic field for a conductor with a current located along the lateral surface of a cylindrical product at a distance d from the center of a metallic cylinder of radius a. Mathematical expressions are obtained to determine the intensity of the magnetic field for r-th and φ-th components, generated by the current of one conductor (or pole with finite angular dimensions). The thickness of the pole with a total current is taken into account, which leads to the replacement of r quantity in the formulas for field strength by effective radius. Mathematical expressions are obtained to determine amplitude and phase of transducer’s signal n-th spatial harmonics, which are generated in the measuring windings located along the surface of the cylindrical object with the angular coordinate φ on a circle of radius d. Experiments have been carried out to confirm the adequacy of the transducer’ proposed model, which showed the difference between the calculated and experimentally obtained values of the EMF of the transducer’ output signal. For instance, for measuring windings with angular coordinates φ = 0° і φ = 180° difference of voltage values is less than 5% and for measuring windings with angular coordinates φ = 30°, 60°, 300° і 330° difference is less than 10%. The method based on the electromagnetic transducer with two magnetized poles and a different direction of current is developed. The universal functions of conversion with use of 1-st and 3-rd spatial harmonics are obtained, also the algorithm of realization of cylindrical wares’ parameters multi-parameter control is offered.

Abstract A measurement system capable of in-situ measurements of formation permeability is described. The measurement method relies upon imaging the distribution of magnetic permeability doped fluid injected into a wellbore system through mutual inductance measurements between pairs of coils, and relating the change in distribution of this fluid over time to a direct measurement of formation phase permeability. Analysis of the mutual inductance measurement method shows a unique response to distributions of magnetic permeability for various coil spacings, and insensitivity to other confounding electrical parameters. The response of the mutual inductance measurement to several magnetic permeability distributions is shown, demonstrating the feasibility of the measurement technique to image the subsurface formation magnetic permeability distribution and provide in-situ measurements of formation phase permeability.

Novel piezoelectric MEMS resonators with magnetic shielding have been developed to mechanically generate RF magnetic fields in the MHz frequency range from static magnetic fields. Thermally evaporated thin film nickel iron (NiFe) (10 to 20 nm) was deposited with a saturation flux density of 0.5 T, coercivity of 500 A/m and a high relative permeability of 3.7 × 103. Aluminum nitride (AlN) resonators developed for high frequency operation, resonate in a contour mode to increase and decrease a gap surrounding the resonator. This gap, 200 to 350 nm, is formed using a silicon sidewall deposition as a sacrificial spacer. Resonators with frequencies up to 60 MHz have been fabricated and tested.

Abstract This paper aims to quantify microporosity and access its impact on reservoir quality properties, to identify Hydraulic Flow Units (HFU) using core porosity and permeability data, to predict HFU and accurately estimate permeability in un-cored intervals/wells. Mercury Injection Capillary Pressure (MICP), Nuclear Magnetic Resonance (NMR) at high pressure (T2 distribution), and Water-Oil relative permeability curve data were used to quantify microporosity. The median pore-throat size was estimated through Windland's R35 equation and modified Kozeny-Carmen equations led to an accurate determination of Flow Zone Indicators (FZI) in each cored interval. Subsequently, Neural Networks were used to predict HFU in un-cored intervals using log data, this model was then extrapolated to estimate permeability in un-cored intervals. Microporosity estimations from MICP are relatively higher compared to NMR and Water-Oil Relative Permeability estimations. Estimations from MICP range from 25-69% while 11-32% is the range of estimations from the other methods. In conjunction to MICP data and clay volume assessment, two distinct zones were identified. The top intervals are characterized by high microporosity levels and steep-convex capillary pressure curves while the bottom intervals have lower microporosity levels and steep-concave capillary pressure curves. Analysis indicated that there are six (6) flow units and that the correlation coefficient (R2) between FZIcore and FZIlog is 99.89% and 91.89% for Kcore and KLog thus validating the model to be used for predictions in un-cored intervals. Through Windland's R35 equation it was concluded that there are two dominant pore throat sizes, meso and macro with ranges between 0.72 – 2.53 μm.

Abstract Tight sandstone reservoirs characterization and evaluation is very difficult based on conventional well log data owing to the extremely low porosity and permeability, and strong heterogeneity. The main accumulation spaces of conventional reservoirs are intergranular pores, and the pore size is the main controlling factor of permeability. However, besides intergranular pores, fractures play much greater important role in accumulating hydrocarbon, improving the pore connectivity and pore structure in tight sandstone reservoirs. Hence, it should be accurately predicted the pore structure dredged by fractures to improve the characterization of tight sandstone reservoirs. Generally, nuclear magnetic resonance (NMR) logging is an effective method to evaluate formation pore structure. However, it cannot be well used in fractured reservoirs because the NMR T2 spectra has no any response for fractures with width <2mm. The borehole electrical image log is usable in characterizing fractured reservoirs. The pore spectrum, which is extracted from the borehole electrical image log, can be used to qualitatively reflect the pore size. Hence, it will play an important role in fractured reservoirs pore structure characterization. In this study, based on the comprehensive analysis of the pore spectra, the corresponding mercury injection capillary pressure (MICP) data and pore-throat radius distributions acquired from core samples, a relationship that connects the 1/POR and capillary pressure (Pc) is proposed. Established a model based on formation classification to transform porosity spectrum into pseudo capillary pressure curve. In addition, a Swanson parameter-based permeability prediction model is also developed to extract fractured formation permeability. Meanwhile, to verify the superiority and otherness of borehole electrical image and NMR log, the model that evaluated reservoirs pore structure from NMR log is also established. Based on the application of the proposed method and models in actual formations, the evaluated pore structure parameters and permeabilities from two types of well log data are compared. The results illustrates that in formations with relative good pore structure, the predicted pore structure parameters and permeabilities from these two types of well log data agree well with the drill stem testing data and core-derived result. However, in low permeability sandstones with relatively poor pore structure, the porosity spectra can be well used to evaluate the pore structure, whereas the characterized pore structure from NMR log is overestimated. With the comprehensive research of reservoirs pore structure and permeability, the fractured tight sandstone formations with development value are precisely identified. This proposed method has greatest advantages that the pore structure of fractured reservoirs can be characterized, and the contribution of fractures to the pore connectivity and permeability can be quantified. it is usable in tight sandstone reservoirs validity prediction.

Abstract A big challenge in tight conventional and unconventional rock systems is the lack of representative reservoir deliverability models for movement of water, oil and gas through micro-pore and nano-pore networks. Relative permeability is a key input in modelling these rocks; but due to limitations in core analysis techniques, permeability has become a knob or tuning parameter in reservoir simulation. Current relative permeability measurements on conventional core samples rely on density contrast between oil/water or gas/water on CT (Computed Tomography) scans and recording of effluent volumes to determine relative fluid saturations during the core flooding process. However, tight rocks are characterized by low porosities (< 10 %) and ultra-low permeabilities (< 1 micro-Darcy), that make effective and relative permeability measurements very difficult, time-consuming, and prone to high errors associated with low pore volumes and flow rates. Nuclear Magnetic Resonance (NMR) measurements have been used extensively in the industry to measure fluid porosities, pore size characterization, wettability evaluation, etc. Core NMR scans can provide accurate quantification of pore fluids (oil, gas, water) even in very small quantities, using T2, T1T2 and D-T2 activation sequences. We have developed a novel process to perform experiments that measure effective and relative permeability values on both conventional and tight reservoirs at reservoir conditions while accurately monitoring fluid saturations and fluid fronts in a 12 MHz 3D gradient NMR spectrometer. The experimental process starts by acquiring Micro-CT scans of the cylindrical rock plugs to screen the samples for artifacts or microcracks that may affect permeability measurements. Once the samples are chosen, NMR T2 and T1T2 scans are performed to establish residual fluid saturations in the as-received state. If a liquid effective permeability test is required, the samples are then saturated with the given liquid through a combination of humidification, vacuum-assisted spontaneous imbibition, and saturation under pressure and temperature. After saturation, NMR scans are obtained to verify the volumes of the liquids and determine if the samples have achieved complete saturation. The sample is then loaded into a special core-flooding vessel that is invisible to the NMR spectrometer to minimize interference with the NMR signals from the fluids in the sample. The sample is brought up to reservoir stress and temperature, and the main flowing fluid is injected from one side of the sample while controlling the pressures on the other side of the sample with a back pressure regulator. The saturation front of the injected fluid is continuously monitored using 2D and 3D gradient NMR scans and the volumes of different fluids in the sample are measured using NMR T2 and T1T2 scans. The use of a 12 MHz NMR spectrometer provides very high SNR (signal-to-noise ratio); and clear distinction of water and hydrocarbon signals in the core plug during the entire process. The scanning times are also reduced by orders of magnitude, thereby allowing for more scans to properly capture the saturation front and changes in saturation. Simultaneously, the fluid flowrates and pressures are recorded in order to compute permeability values. The setup is rated to 10,000 psi confining pressures, 9000 psi of pore pressure and a working temperature of up to 100 C. Flowrates as low as 0.00001 cc/min can be recorded. These tests have been done with brine, dead and live crudes, and hydrocarbon gases. The measured relative permeability values have been used successfully in both simulation and production modelling studies in various reservoirs worldwide.

Abstract Multiphysics finite element modeling process is derived to predict vibration and noise due to magnetic forces within a permanent-magnet brushless DC motor over a variable speed range under healthy and eccentric faulty conditions. Transient analysis for magnetic force in two-dimensional electromagnetic model is carried out over a variable speed range. To keep cyclic symmetry mesh and avoid numerical source of noise, the method of effective air gap layer is applied and manipulated with relative permeability derived for static and dynamic eccentric rotating condition depending on rotation angle and eccentric shift. Using discrete Fourier transformation and electromagnetic-structural one-way coupling schemes, magnetic harmonic forces for a range of rotation angular speed are imported and applied on stator’s inner surfaces. Vibration characteristics are calculated for a three-dimensional full finite element model of the motor in harmonic response analysis. Finally, surface velocities are imported and applied on acoustic domain using fluid-structure interaction (FSI) one-way coupling. Noise radiated from motor housing including front and end caps is evaluated. The waterfall diagram of equivalent radiation pressure level (ERPL) and sound pressure level (SPL) contour plotting in function of rotation angular speed and frequency is obtained in multiple RPM harmonic structural and acoustic analyses. The vibro-acoustic feature pattern could be utilized in faulty detection.

Reliable and real-time assessment of directional permeability and saturation-dependent capillary pressure are utterly important because they significantly affect the exploitation strategies. Conventional well-log-based methods (e.g., NMR-based, saturation-height analysis, resistivity-based, correlation-based) are either highly dependent on calibration efforts or rely on model parameters which are difficult to obtain in real-time and make them dependent on core measurements. Moreover, most conventional methods for assessment of directional permeability and saturation-dependent capillary pressure fail in the presence of multi-modal pore-size distribution. Recent publications suggested that integration of transverse Nuclear Magnetic Resonance (T2 NMR) and resistivity measurements enables assessment of pore-throat-size distribution as well as permeability and capillary pressure. However, the reliability of these methods is questionable in rocks with complex/multi-modal pore geometry. The objectives of this paper include (a) reliably estimating a variable constriction factor (a geometric parameter which relates the pore- and throat-size) in rocks with complex pore geometry to accurately quantify pore geometry, which is the main contribution of this work, (b) developing a new rock physics workflow for integrating NMR and electrical conductivity for assessment of permeability and capillary pressure that takes into account a variable constriction factor, and (c) verifying the reliability of the introduced workflow using core scale measurements. The proposed workflow starts with calculating pore-body-size distribution from NMR T2 distribution. Then, we combine electrical resistivity and pore-size distribution to estimate the distribution of constriction factor in the pore structure. Next, we determine pore- throat-size distribution using the estimated variable constriction factor. We then introduce a new permeability model which takes variable constriction factor into account. The inputs to the permeability model include throat-size distribution, tortuosity, and porosity. Finally, we calculate saturation-dependent capillary pressure using the estimated throat-size distribution. We successfully verified the reliability of the introduced workflow in the core-scale domain in carbonate rock samples with complex pore structure. The permeability estimates obtained by the new workflow yielded less than 7% average relative error when compared against core measurements. We also observed a good agreement between the throat-size distribution and capillary pressure estimated from the new workflow and the ones acquired from MICP (mercury injection capillary pressure) measurements. Results also confirmed that integration of a variable constriction factor improves directional permeability estimates compared to cases where an effective constriction factor was used to quantify pore-throat size distribution in rocks with multi-modal pore-size distribution.