Interelement Decoupling Strategies at UHF MRI

Moving to the ultrahigh field magnetic resonance imaging (UHF MRI) brought many benefits such as potentially higher signal-to-noise ratio, contrast-to-noise ratio, and improved spectral resolution. The UHF MRI regime also introduced some challenges which could prevent full exploitation of mentioned advantages. A higher static magnetic field means increase in Larmor frequency, which further implies the shorter wavelength in a tissue. The shorter wavelength causes interferences of the RF signal and inhomogeneous excitation, which can be partially resolved by the introduction of the multichannel coil arrays. The biggest problem in UHF multichannel densely populated arrays is the existence of the interelement coupling, which should be minimized as much as possible. This article presents the nonconventional, recently developed decoupling techniques used in UHF MRI.

Improvement of power transfer efficiency of hexagonal coil arrays in misalignment conditions

<span>Wireless charging by transferring energy between two objects using electromagnetic fields commonly called Wireless power transfer is an alternative technology that is physically installed in an electric vehicle (EV) to charge. Parking alignment is a very important factor in driver behavior that affects Power transfer efficiency (PTE). The proposed hexagonal coil array design in this experiment is to optimize PTE and receiver coil size. The experimental results show that PTE in the tangential boundary plane Misalignment increases by 5-10% when compared to coil array circles and increases by 82% when compared to single coil circles. </span>

EFFECTS OF THE DEVIATION ANGLE OF THE BOREHOLE IN THE INDUCTION ANISOTROPY LOGS

ABSTRACT. This paper performs an analysis of the effects of the well’s deviated angle on the tensor triaxial induction tool signals within a thinly sand-shale laminated reservoirs and their equivalent intrinsic anisotropic models. The responses from coaxial and coplanar coil arrays in inclined wells are studied in detail, including the analysis of their apparent anisotropy logs, as well as their estimation of sand conductivity in the environments with a structural anisotropy.The dip angle effects are modeled in simple geometries as one-dimensional (1D) models, neglecting the presence of the borehole and the invasion zones, since they provide basic insight for understanding tool responses in more complex models. The results show a strong sensitivity of both the coaxial and coplanar signals to the deviated angle. It is verified that the anisotropy values are significantly reduced when the well is inclined as compared to what is found for the true vertical case, even for inclinations small enough for the wells to be classified as technically vertical (30 degrees or less). Therefore, the angle effects must be carefully considered, even for technically vertical wells. Otherwise, potential finely laminated reservoirs can be underestimated or even ignored.Keywords: deviated well logging, tensor induction tool, laminated reservoirs, electrical anisotropy.RESUMO. Neste trabalho é apresentado como as incertezas na interpretação sísmica impactam na cons-trução do modelo de velocidades e na conversão tempo-profundidade resultante. A área de estudo de estudo está localizada na Bacia de Campos, Brasil. O principal objetivo deste trabalho é mostrar como os dados de entrada e parâmetros afetam na modelagem de velocidade e conversão tempo x profundidade. A metodologia é comparar três diferentes cenários para calibração da velocidade de processamento e imageamento com as interpretações sísmicas e de poços: o cenário 1 utiliza ajuste por horizonte com marcador geológico e raio de influência 5 km; no cenário 2 é utilizada as tabelas tempo-profundidade, raio de influência 5 km por krigagem com derivada externa; e o cenário 3 utilizou-se tabelas tempo-profundidade, raio de influência 2 km por krigagem com deriva externa. O controle de qualidade dos três modelos de velocidade são avaliados pela conversão dos horizontes, seções sísmicas e perfis de pseudo-impedância. No cenário 1, os horizontes convertidos apresentam menores diferenças de profundidade em relação aos marcadores comparados aos demais cenários. Por outro lado, os cenários 2 e 3 apresentam maiores correlações entre o sismograma sintético e a seção sísmica convertida para o cenário 1. Palavras-chave: poços desviados, ferramentas triaxiais, reservatórios laminados, anisotropia elétrica.