Full Azimuth Research Articles

Application of GAN to Resolution Enhancement of LWD Real-Time Image Logs to Support Decision Making

In the current scenario of project management, where the agility and optimization of operations have been prioritized, the practice of logging while drilling (LWD) has gained space compared to traditional wireline logging. In theory, acquiring quality petrophysical properties during drilling brings greater agility in decision making about completion and optimizes operation costs. However, regarding borehole image logs, due to limitations in transmission capacity, the actual available data in real time contain about 50% (for resistivity images) of the full azimuth information, being insufficient for the identification of critical geological structures capable of impacting the communication between production or injection zones or the quality of cementation, such as fractures, caves, and geomechanical collapse zones. The tool’s memory data with the full information may take a few days after the end of drilling to be delivered by the service company, which in some cases is not enough for fast decision making regarding completion. In this work, we tested models based on generative adversarial neural networks (GANs) to reconstruct the complete memory data based on real-time input. As in conventional GAN schemes, a generator is trained to receive a real-time input and create a “memory-like” image, while a discriminator is trained to tell real and fake images apart. To regularize the convergence of training, we used an architecture known in the literature as CycleGAN, where another generator-discriminator pair is trained simultaneously to do the reverse process, recreating the real-time data. Variations of the training process and data sets were used to generate different CycleGAN models. They were trained using logs of presalt reservoirs in Buzios Field, and performance was assessed on logging intervals not seen by the algorithms during training. The results achieved so far have been very promising, as in certain intervals, resultant models were able to capture the presence of fractures and caves. This methodology represents a way of circumventing telemetry limitations, where missing information is added indirectly to the real-time data as the artificial intelligence (AI) algorithm learns the main characteristics of a field/reservoir. Therefore, previous knowledge from the field can be used to continuously optimize future operations, efficiently incorporating the available database into the workflow of petrophysicists for the recognition of geological and geomechanical structures in time to support decision making in completion operations.

Forge ahead in acquisition and model building via full-waveform inversion: Gulf of Mexico case study

Full-waveform inversion (FWI) has proven itself an essential tool for velocity model building using seismic data. In recent years, the geophysical community has made substantial progress in developing FWI to overcome some long-standing limitations, such as handling cycle skipping, better using reflection energy, including more physics in the inversion algorithms, and increasing inverted frequencies to achieve higher resolution. FWI does not only target the larger and midscale model updates, more and more FWI examples were presented with increased resolution which allows for extraction of FWI derived reflectivity. Interrogating the FWI kernel with given geology and acquisition geometry can provide critical information on how the acquisition design should be optimized to provide FWI a better opportunity to update the velocity model at target depth, especially in the deep part of the model. When the acquisition geometry is different in terms of offsets, azimuthal coverage, and the minimum frequency in the recording, it can be analyzed to design workflows to enable FWI to optimally update the model parameters. Obviously, recent ocean-bottom node acquisitions that record long offsets, full azimuth, and low frequencies have made FWI shine in the seismic industry. Modifying and reshaping a complex salt geometry is one of the ultimate goals of FWI. In addition to the salt boundary being an issue, there is a potential cycle-skipping problem associated with uncertainties of large salt bodies missing or misplaced even though the frequencies used to start FWI are becoming lower due to the advancement in seismic acquisition and FWI algorithms. Furthermore, if the FWI-predicted data are simulated with an acoustic engine, it could pose amplitude and phase discrepancies at high-velocity contrast interfaces. Elastic FWI alone has been proposed as a means of overcoming these challenges associated with salt and regions with high-velocity contrast. We determine the FWI progress of the past few decades with the latest examples from different acquisition geometries.

Generation of Multiple Frames for High Resolution Video SAR Based on Time Frequency Sub-Aperture Technique

Video Synthetic Aperture Radar (ViSAR) operating in spotlight mode has received widespread attention in recent years because of its ability to form a sequence of SAR images for a region of interest (ROI). However, due to the heavy computational burden of data processing, the application of ViSAR is limited in practice. Although back projection (BP) can avoid unnecessary repetitive processing of overlapping parts between consecutive video frames, it is still time-consuming for high-resolution video-SAR data processing. In this article, in order to achieve the same or a similar effect to BP and reduce the computational burden as much as possible, a novel time-frequency sub-aperture technology (TFST) is proposed. Firstly, based on azimuth resampling and full aperture azimuth scaling, a time domain sub-aperture (TDS) processing algorithm is proposed to process ViSAR data with large coherent integration angles to ensure the continuity of ViSAR monitoring. Furthermore, through frequency domain sub-aperture (FDS) processing, multiple high-resolution video frames can be generated efficiently without sub-aperture reconstruction. In addition, TFST is based on the range migration algorithm (RMA), which can take into account the accuracy while ensuring efficiency. The results of simulation and X-band airborne SAR experimental data verify the effectiveness of the proposed method.

Simulating Large-Scale Streamer and OBN Acquisition over Subsalt Targets — an Example of Successful Remote Collaboration Between Survey Design and Survey Evaluation

In this article we look at how ray-based wavefront modelling can be used to evaluate competing acquisition techniques with significantly different illumination properties and associated acquisition cost. We compare subsurface illumination of complex sub-salt reservoirs typical of those found in the Gulf of Mexico for a variety of towed-streamer and full azimuth long offset ocean bottom node surveys. Single, dual and triple azimuth towed-streamer surveys are considered. This project was accomplished using a new connector between ACTeQ’s survey design and optimization software and Norsar’s 3D modelling software. This project is an excellent example of competitors collaborating to better achieve a customer’s needs. The project was also accomplished in a fully remote environment, and none of the authors were in the same city at any time during the project. Remote collaboration is becoming an increasingly effective low-carbon approach to complex challenges.

Full waveform inversion of a Brazilian pre-salt OBN dataset using a concentric circle source geometry

We have designed a workflow to apply full-waveform inversion (FWI) to a new type of acquisition recorded on ocean-bottom nodes (OBNs) in the Brazilian presalt area. The data set consists of three large-radius concentric circles of seismic source points recorded on OBN placed within the area of the circles. This geometry provides full azimuth distribution and benefits from long offsets in which the effect of diving waves is strong. These diving waves carry information about the presalt targets of interest. In the FWI workflow, we retrieve the P-wave velocity using the density as a propagation parameter. We test three objective functions: ℓ2-norm, ℓ1-norm, and nonparametric residuals objective function (NPR-FWI), which have different abilities to handle low signal-to-noise ratio data. In our inversion tests, the ℓ1-norm and NPR-FWI retrieve more information about the presalt reservoir than the ℓ1-norm. We find through several inversion experiments that we can recover structures related to the presalt reservoir, demonstrating the potential for this new type of OBN circular source geometry. We also discuss implications for low-cost data acquisition that take advantage of the sparse nature of sources and receivers needed in this survey geometry, including its extension to time-lapse target-oriented reservoir monitoring.

3-D Printed Annular Linear-to-Circular Dielectric Polarizer and Its Applications to Omnidirectional and Multibeam Antennas

This article presents a 3-D printed dielectric polarizer. It is constituted by a number of annually arranged dielectric slabs, and each slab is 45° rotated with respect to the azimuth plane. It is able to transform the polarization state of the waves in azimuth plane from linear to circular. Based on the polarizer, two circularly polarized (CP) antenna designs are proposed. One of them is an omnidirectional CP antenna, and the other is a multibeam CP antenna with capability of full azimuthal scanning. They are fed by a dielectric filled biconical structure and six corner reflectors, respectively. Their polarizers are individually designed with different geometric parameters. Both antennas are one-piece configurations and can be directly 3-D printed without assemblies in later stage. Partial surfaces of the antennas are coated with copper films by an electroplating technique to act as the necessary metal components. To validate the design ideas, two prototypes are demonstrated in X-band. Experimental results show that the omnidirectional antenna can achieve a wide 3 dB axial ratio (AR) bandwidth of 28.3% from 8.5 to 11.3 GHz and a peak gain of 3.3 dBic. Meanwhile, the multibeam antenna is with a wide 3 dB AR bandwidth of 22.4% from 8.7 to 10.9 GHz and a peak gain of 9.2 dBic. Within the AR bandwidth, the AR values in full azimuth plane are lower than 3 dB.

A Low-Profile Microstrip Vertically Polarized Endfire Antenna With 360° Beam-Scanning and High Beam-Shaping Capability

A novel low-profile vertically polarized planar endfire smart antenna that can achieve 360° beam-steering and high beam-shaping capability is proposed. The microstrip antenna is printed on a single thin substrate with a vertically polarized omnidirectional driven source and 36 tunable slot-integrated microstrip vertically polarized resonators (SMVR) for shaping the endfire beams. To verify the design approach, a prototype operating at the 5 GHz WLAN band is fabricated and tested. The results show that the antenna operates from 5.55 to 5.75 GHz and is capable of scanning a single endfire beam from 0° to 360° in the full azimuth plane. The scanning resolution and the maximum realized gain are 15° and 8.2 dBi, respectively. Moreover, multiple radiation pattern shapes including omnidirectional beam, dual-beams, and tri-beams can also be generated by the antenna. The overall antenna height is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.06~\lambda $ </tex-math></inline-formula> at 5.6 GHz. This design provides a new antenna configuration for low-profile vertically polarized endfire beam-steering and beam-shaping antenna and is promising for future wireless communication systems with lost-cost beamforming property.

3‐D printed circularly polarized multibeam antenna array with full azimuth scanning capability and wideband characteristic for 5G millimeter‐wave applications

This paper presents a wideband circularly polarized (CP) multibeam antenna array, which is with full azimuth scanning capability and operates in Ka band for 5G applications. It adopts a circular array configuration and consists of 18 elements with a simple structure. Regarding to each element, it is fed by a 90° bent rectangular waveguide and employs a simplified single dielectric slab polarizer to produce CP waves. Within the axial ratio bandwidth (ARBW), the proposed element can achieve a stable half power beamwidth (HPBW) of 29 ± 7°, while, the 3-dB AR beamwidth is larger than the HPBW. By switching the active elements, the proposed array can realize 360° beam steering in azimuth plane, while, the HPBW and the 3-dB AR beamwidth cover the entire plane. To simplify the fabrication process, dielectric and metal 3-D printing technologies are employed for processing. Experimental results indicate that the proposed array can achieve a 40.5% 3-dB ARBW which almost covers the entire Ka band from 26.2 to 39.5 GHz and a gain of 9.9 ± 1.5 dBic. The front-to-back ratio (FBR) of each beam is higher than 19 dB. In contrast to conventional designs, the proposed antenna features wide band, simple structure, and ease of fabrication.

360° Polarization Control of Terahertz Spintronic Emitters Using Uniaxial FeCo/TbCo2/FeCo Trilayers

Polarization control of THz light is of paramount interest for the numerous applications offered in this frequency range. Recent developments in THz spintronic emitters allow for a very efficient broadband emission, and especially unique is their ability of THz polarization switching through magnetization control of the ferromagnetic layer. Here we present an improved scheme to achieve full 360° nearly coherent polarization rotation that does not require multipolar or rotating external magnetic bias nor complex cascaded emitters. By replacing the FM layer of the spintronic emitter with a carefully designed FeCo/TbCo2/FeCo anisotropic heterostructure, we experimentally demonstrate Stoner–Wohlfarth-like coherent rotation of the THz polarization over a full 2π azimuth only by a bipolar variation of the strength of the hard axis field, and with only a negligible decrease in the emission efficiency as compared to standard Pt/CoFeB/W inverse spin Hall emitters. THz measurements are in agreement with our model of the nonperfect Stoner–Wohlfarth behavior. These emitters are well adapted for the implementation of polarimetric characterization not requiring any mechanically rotating polarizing elements. An example is given with the characterization of the birefringence in a quartz plate.

Annular Surface Plasmon Polariton-Based Frequency-Scanning Leaky-Wave Antenna for Full Azimuth Coverage

This article presents a single-layered annular surface plasmon polariton (SPP)-based leaky-wave antenna (LWA) for full azimuth beam scanning in 60 GHz applications. The groundless annular SPP transmission line (TL) has a special feeding mechanism that can be operated at 60 GHz in the SPP mode. Periodically radiating circular patches with gradually smaller sizes near the TL create an additional momentum that helps convert the slow wave SP mode into the radiating leaky mode. This results in frequency-dependent continuous beam scanning in the azimuth plane. The theoretical, numerical, and experimental results of the proposed device agree well. The antenna has an overall scanning range of 268°, −10 dB impedance BW of 15.33%, and a peak gain of 19.7 dBi with an average sidelobe level (SLL = −10 dB) and a cross-polar level of −20 dB. Owing to the low-profile compactness and improved performance, the proposed single-layered LWA is a promising candidate for 60 GHz V-band millimeter (mm)-wave applications.

Performance Evaluation of Radio Frequency Interference Measurements from Microwave Links in Dense Urban Cities

Radio frequency interference (RFI) constitutes a significant problem in achieving a good quality of service in radio links. Several techniques have been proposed to identify and mitigate RFI in wireless networks. However, most of these techniques are not generalized for all propagation environments due to varying geographical features from one environment to another. The need for extensive frequency scan measurements on the links to identify the available channels, evaluate the performances of the links, and detect RFI in the channels becomes imperative. This study presents a performance evaluation of frequency scan measurements from active microwave links comprising eighteen base stations. The measurements equipment included a spectrum analyzer and a 0.6 m antenna dish. The frequency scans were taken at 6 GHz, 7 GHz, and 8 GHz with full azimuth coverage of the horizontal and vertical polarization. Measured data were processed to determine the available frequencies and RFI in the channels. The histogram and probability density function of the frequency scans were computed. The cumulative distribution functions were determined, and the statistical error characteristics of the frequency scans for the estimated normal distribution and the estimated fitness curve were derived. The short-time Fourier transform of the noisy signal was obtained, and the signal without noise was recovered using the inverse short-time Fourier transform. Analysis of the scanned signals before and after the noise removal is demonstrated. The denoised signals compare favorably with related results in the preliminary literature. Overall, these frequency scans would be beneficial in evaluating RFI measurements and spectrum planning and hold great promise for designing robust RFI detection algorithms for future wireless systems.

Fast digital multi-beam search method for active phased array antenna system with full azimuth beam steering

This paper proposes a multi-beam search method based on an active phased array antenna system using digital beamforming. It includes initial beamforming, valid beam selection, and beam angle estimation using phase comparison mono pulses for multi-channel signals. To verify DoA estimation error, simulation and measurement are performed using the proposed antenna system. As a result, we confirm the performance of estimating each channel's angle and the beam directional error within 0.5°.

NEW TECHNOLOGIES OF SEISMIC EXPLORATION IN UKRAINE

Development of technologies, growth of trends of reducing impact on environment and challenging tasks, which oil and gas producers face, make introduction of new technologies in seismic exploration field unavoidable. As a key tool of prospecting, exploration and reconnaissance of hydrocarbons, seismic exploration is usually restricted by terrain conditions. Urban, wooded and marshy lands, protected areas, river valleys, mountain areas often make seismic exploration impossible or signifi cantly impact its quality and efficiency. One of the modern trends enabling resolution of the issues related to impact on environment is to switch to cable-free registration systems (wireless seismic), so called low impact seismic. Due to the use of cable-free equipment, this new technology makes it possible to reduce impact on environment during field works, as equipment is delivered to the place of installation with no special heavy machinery involved. On the other hand, cable-free systems of seismic acquisition allow to resolve complex tasks of exploration and appraisal studies. Firstly, carry out exploration of hard-to-reach territories, including protected environmental areas, which until now remain unexplored or slightly explored. Managing seismic cables in such conditions is very complicated or impossible. Cable-free technologies allow easily resolving such issues due to both minimum impact on environment and simple and quick placement of receivers. Flexibility and easy scaling of wireless seismic adds to its advantages versus conventional survey. Kilometres of wires are not needed, which allows to easily increase the number of receiver channels and conduct high-density full azimuth seismic survey with single seismic receivers at deep structures, thus, significantly increasing quality of the data received. The pilot project successfully completed at Khoroshivska area by joint efforts of DTEK Oil&amp;Gas LLC and LLC Denimex Geo LLC confi rms in full advantages of wireless solutions revealing new opportunities for the use of seismic exploration at areas previously hard to reach and allowing implementation of high density acquisition projects.

Study of a hemispherical metamaterial lens made of parallel printed circuit boards with metal diffusers of small electrical dimensions

Antenna systems based on hemispherical lenses allow full azimuth scanning or electronically controlled sector scanning. The article presents a numerical simulation of a broadband multi-beam antenna system based on a hemispherical metamaterial lens made of parallel printed circuit boards with metal diffusers of small electrical dimensions. The effective parameters of a metamaterial based on printed Jerusalem crosses with welded-in transverse metal pins are investigated. The selected geometric dimensions of the metamaterial made it possible to reduce the effect of anisotropy. Directional patterns are considered when a lens is excited by a system of broadband vibrators with two orthogonal polarizations. For each polarization, conclusions are drawn about the operating range and the magnitude of the losses. The results obtained in this work are planned to be used in the future in the design of wideband lens antennas from parallel printed circuit boards.

A New DOA Algorithm for Spectral Estimation

Uniform linear arrays (ULAs) are the most commonly used configurations for the direction-of-arrival estimation of radio signals in many wireless communication applications due to its simplicity. However, this configuration does not provide uniform estimation and deteriorates in performance for the grazing incidences. In this work, we solve this problem by modifying the structure of a conventional ULA. This new confirmation has two extra antenna elements at the ends of the array. These extra elements will automatically activate when the source signals are impinging for the grazing incidences. We modify the multiple signal classical algorithm and develop an improved array signal model to obtain the high-resolution pseudo-spectrum of the received signals for full azimuth angles. The performance of the proposed method is compared with the various well-known methods in many practical scenarios. Finally, total Root Mean Square Error is examined over a wide range of Signal to Noise Ratio. Simulation results show that the proposed method outperforms the well-knows methods and provides the accurate and uniform estimation of narrowband signals for end fire array angles which fall in the range $$\left( { - 70^{{^\circ }} \le \theta \le - 90^{{^\circ }} } \right)$$ and $$\left( {70^{{^\circ }} \le \theta \le 90^{{^\circ }} } \right)$$ , at middle angles $$\left( { - 60^{{^\circ }} \le \theta \le 60^{{^\circ }} } \right)$$ and at boresites which is very useful in 5G and beyond mobile communication.

Wideband Multibeam SIW Horn Array With High Beam Isolation and Full Azimuth Coverage

This communication presents a Ka-band multibeam substrate-integrated waveguide (SIW) horn array implemented in a single-layer planar substrate. By conforming the array into a circular shape, the horn array covers full 360° azimuth range with 12 beams. Every adjacent beam overlaps each other at the half-power beam shoulders. A wideband matching is obtained with -10 dB reflection coefficients from 27.5 to 38 GHz. By suppressing the side-lobe levels to be lower than -20 dB, the mutual coupling between each SIW horn is less than -45 dB from 28 to 38 GHz. With a thin radiating aperture of 0.1 6λ, a stable realized gain of each beam is achieved around 9.5 dBi, whereas it increases to 12.9 dBi when there is a conducting reflector closely beneath it. Due to the reflector, the main radiation directions tilt 30°, which enables the proposed multibeam antenna to be mounted on the ceiling while maintaining the communication for multiple users below. Results with a manufactured prototype well demonstrate the multibeam performance both in simulation and measurement with good agreement. In addition, it is compact and easy to be fabricated with common printed circuit board (PCB) techniques, also suitable to be integrated into microwave systems. It is promising for the application in beam-switched, multiple-input multiple-output (MIMO), and omnidirectional systems.

Fast Double-Directional Full Azimuth Sweep Channel Sounder Using Low-Cost COTS Beamforming RF Transceivers

This paper presents a multipath component (MPC) parameter estimator that uses a double-directional (D-D) channel sounding system in WiGig millimeter-wave bands. It employs low-cost commercial-off-the-shelf (COTS) RF transceivers capable of beam steering within an azimuth angle range of ±45°; the transmit power is approximately 31 dBm, equivalent isotropic radiated power (EIRP), including a total antenna gain of approximately 19 dBi. The half-power beam widths in the azimuth and elevation planes are 6° and 45°, respectively. A fast D-D channel acquisition in 360° full azimuth range can be achieved by developing a 4 ×4 multiple-input-multiple-output (MIMO) time division-multiplexing (TDM) scheme that enables simultaneous use of four antenna arrays at both sides of the transmitter and receiver. The beam switching for all combinations ( 48 ×48 = 2304) with 12 beams at each array requires less than 200 ms, excluding optional procedure related to data storage. A high-resolution MPC extraction method was developed from the D-D angular delay power spectra obtained using the sub-grid CLEAN algorithm, which is applicable when phase coherence among multiple snapshots obtained via the beam-switching measurement cannot be guaranteed. Furthermore, the operation of the developed system was validated via a measurement at 58.32 GHz in an office floor of a university laboratory. From the data analysis, the cluster properties and the corresponding scattering processes were identified.

Gluon polarization measurements from longitudinally polarized proton-proton collisions at STAR

The gluon polarization contribution to the proton spin is an integral part to solve the longstanding proton spin puzzle. At the Relativistic Heavy Ion Collider (RHIC), the STAR experiment has measured jets produced in mid-pseudo-rapidity, |η| < 1.0, and full azimuth, ϕ, from longitudinally polarized pp collisions to study the gluon polarization in the proton. At center of mass energies = 200 and 510 GeV, jet production is dominated by hard QCD scattering processes such as gluon-gluon (gg) and quark-gluon (qg), thus making the longitudinal double-spin asymmetry (ALL ) sensitive to the gluon polarization. Early STAR inclusive jet ALL results at = 200 GeV provided the first evidence of the non-zero gluon polarization at momentum fraction x > 0.05. The higher center of mass energy = 510 GeV allows to explore the gluon polarization as low as x ∼ 0.015. In this talk we will present the recent STAR inclusive jet and dijet ALL results at = 510 GeV, and discuss the relevant new analysis techniques for the estimation of trigger bias and reconstruction uncertainty, the underlying event correction on the jet energy and its effect on jet ALL . Dijet results are shown for different topologies in regions of pseudo-rapidity, effectively scanning the x-dependence of the gluon polarization.

A 2-D Beam-Scanning Bessel Launcher for Terahertz Applications

This article proposes a novel nondiffractive Bessel beam launcher based on discrete dielectric lens (DDL) antenna with 2-D beam-scanning capability operating at 300 GHz. The terahertz (THz) Bessel beam launcher consists of two identical in-plane rotatable DDLs fed by a commercially available pyramid horn. First, the two thin and lightweight DDLs can transform the quasi-Gaussian beam with spherical phase front from the feed horn into a well-collimated and confined pseudo-Bessel beam. Second, we demonstrate that simultaneous in-plane rotation of the two DLLs in the same and opposite directions can steer the generated Bessel beam in the azimuth and elevation, respectively. Hexagonal dielectric post is employed as the element of the DDL, whose height is tuned from pixel to pixel to realize the required aperture phase distribution. 3-D printing technology was utilized to fabricate the two DDLs aiming at simplifying the manufacturing process and reducing the cost. The theoretically calculated, simulated, and measured results reveal that the designed THz DDL can generate 2-D scanning nondiffractive Bessel beam with a large field of view (FoV) of 86.2° and full azimuth coverage. The proposed 2-D scanning THz Bessel beam launcher can find widespread applications in THz fast noncontact detection, tracking, and imaging systems.

Path Loss and Directional Gain Measurements at 28 GHz for Non-Line-of-Sight Coverage of Indoors With Corridors

Adequate coverage with high-gain antennas is a key to realizing the full promise of the bandwidth available at mm/cm wave bands. We report extensive indoor measurements at 28 GHz (1000 links, 9.9 million individual power measurements, 10 offices, 2 buildings), with/without line of sight (LOS) using a continuous wave channel sounder, with a 10° spinning horn, capable of capturing a full azimuth scan every 200 ms, in up to 171 dB path loss to characterize coverage with 90% confidence level. The environment had prominent corridors and rooms, as opposed to open/mixed offices in latest 3GPP standards. Guiding in corridors leads to much lower RMS azimuth spread (7° median in corridor non-LOS (NLOS) versus 42° in 3GPP) and higher penetration loss into rooms and around corners (30–32 dB, some 12 dB more loss than 3GPP at 20 m NLOS). Measured path gain in NLOS is predicted by a mode-diffusion model with 3.9 dB RMS error. Scattering degraded azimuth gain by up to 4 dB in the corridor and 7 dB in rooms with 90% probability. Link simulations in a canonical building indicate every corridor needs an access point to provide 1 Gb/s rate to adjoining rooms within 50 m using 400 MHz of bandwidth.