Deep Tow Research Articles

Insights into the depositional setting for the Gippsland Basin from modern basin-wide 3D datasets

The Gippsland Basin is a prolific hydrocarbon basin, with gas and oil initially discovered in the Barracouta (1965) and Kingfish (1967) fields. Historically the basin was covered with a patchwork of legacy 3D seismic surveys acquired from 1980 to mid-2000s, shot with old technology resulting in sub-optimal imaging of the subsurface. CGG reprocessed 10,190 km2 of legacy 3D data as part of their ReGeneration project in 2018 and in 2020 acquired 8751 km2 of long offset, deep tow and undershot seismic data. With these data sets, Woodside has been able to extract images of the regional depositional systems through the basin’s evolution. These observations range in scale from interpretation of individual channels and channel belts to the distribution of the major shoreface systems and marine fans.

Marine self-potential measurement tool for autonomous underwater vehicle.

Marine self-potential (SP) measurement is commonly conducted for seafloor sulfide detection and hydrothermal vent studies in deep water using instruments towed close to the seafloor. However, this method has the following shortcomings: (1) It relies on ships for deep towing, and the need for a dedicated ship time lowers its efficiency. (2) Owing to complex topography, most towed instruments are located far from the seafloor to ensure safety, resulting in large effective signal attenuation and low signal-to-noise ratio. (3) The measurement direction is generally a single axis, with only the electric field of the axial component observed, providing limited information. With the gradual maturity of autonomous underwater vehicle (AUV) technology, it has become possible to mount marine SP measurement tools on AUVs for detection. Compared with conventional methods, this method has significant advantages in terms of efficiency, signal-to-noise ratio, and multicomponent observation. The proposed tool is a lightweight underwater device having a compact design and low power consumption, making it suitable for AUVs. The overall volume of the tool is D50mm × L350mm, and the underwater weight is 0.6kg. Chopper amplification technology ensures the low-noise measurement of electric field signals. In addition, the reformed electrodes enhance stability, thereby reducing the mechanical vibration noise. Laboratory test results show that the noise of the data logger is 7.8 nV/rt (Hz)@1Hz. The marine test conducted in the southwest Indian Ocean verified the reliability of the proposed marine SP measurement tool. The maximum working depth was 4000m. The test lasted ∼25 h, and the effective electric field data were collected for ∼17 h. This survey found a maximum SP anomaly of 0.55 mV/m in the Yuhuang hydrothermal field, which provided effective data support for the discovery of new seafloor sulfide anomalies.

Review of Nodule Mineral Image Segmentation Algorithms for Deep-Sea Mineral Resource Assessment

A large number of nodule minerals exist in the deep sea. Based on the factors of difficulty in shooting, high economic cost and high accuracy of resource assessment, large-scale planned commercial mining has not yet been conducted. Only experimental mining has been carried out in areas with high mineral density and obvious benefits after mineral resource assessment. As an efficient method for deep-sea mineral resource assessment, the deep towing system is equipped with a visual system for mineral resource analysis using collected images and videos, which has become a key component of resource assessment. Therefore, high accuracy in deep-sea mineral image segmentation is the primary goal of the segmentation algorithm. In this paper, the existing deep-sea nodule mineral image segmentation algorithms are studied in depth and divided into traditional and deep learning-based segmentation methods, and the advantages and disadvantages of each are compared and summarized. The deep learning methods show great advantages in deep-sea mineral image segmentation, and there is a great improvement in segmentation accuracy and efficiency compared with the traditional methods. Then, the mineral image dataset and segmentation evaluation metrics are listed. Finally, possible future research topics and improvement measures are discussed for the reference of other researchers.

The latest development of Marine controllable source electromagnetic transmitter

Marine Controlled-Source Electromagnetic (MCSEM) methods have been recognized as an important and effective tool in accurate analysis of shallow electrically resistive structures such as oil, gas and gas hydrate. However, the MCSEM performance in the deep ocean is strongly affected by the hardware design, especially the transmitter system. We have developed a series of deep-towed MCSEM transmitter systems. The design of the transmitter system meets serious challenges such as long-distance and high-voltage transmission, water sealing under high-pressure, the real-time monitoring of seafloor status information 4 km below the sea-surface. In this paper, we present the latest research and development of the MCSEM transmitter systems by presenting key technologies in hardware development and implementation details. The deep tow transmitter system consists of three parts: the deck unit, the deep tow cable and the deep tow unit, which can transmit the high frequency and high power to the seawater, maintaining a high-speed data communication with control center which in the ship’s lab. We conducted several experiments in the South China Sea from August of 2010, to November of 2019. The results showed that the development of the transmitter is successful and it can be used for oil, gas and gas hydrate exploration as an effective source.

An Underwater Photogrammetric Application to Generate Micro-Bathymetry Data for Benthic Habitat Mapping and Analysis at Arctic Ocean

Abstract The Ocean Floor Observation and Bathymetry System (OFOBS) is an underwater survey platform, which is designed and developed for research in the Polar Regions by the Alfred Wegener Institute (AWI). The tailored deep tow system brought a new perspective and clarity from Arctic Ocean by its optical and acoustic sensors. During the PS101 expedition at the Karasik seamount, OFOBS provides a novel picture of megafauna’s habitats. In this study, we develop a methodology to convert the imagery dataset to micro-bathymetry in order to provide primary data for object detection and habitat mapping which will provide a better understanding of arctic benthic habitats. The methodology is based on the underwater photogrammetry workflow and two different point cloud classification methods adopted for sponge detection in 3D point clouds, to facilitate habitat mapping with a focus on the central of Karasik seamount where an extensive and dense assemblage of the Geodia sponges is dominating the seafloor.

Seafloor massive sulphide exploration using deep-towed controlled source electromagnetics: Navigational uncertainties

SUMMARY Deep-towed geophysical surveys require precise knowledge of navigational parameters such as instrument position and orientation because navigational uncertainties reflect in the data and therefore in the inferred geophysical properties of the sub-seafloor. We address this issue for the case of electrical conductivity inferred from controlled source electromagnetic data. We show that the data error is laterally variable due to irregular motion during deep towing, but also due to lateral variations in conductivity, including those resulting from topography. To address this variability and quantify the data error prior to inversion, we propose a two-dimensional perturbation study. Our workflow enables stable and geologically reliable results for multi-component and multi-frequency inversions. An error estimation workflow is presented, which comprises the assessment of navigational uncertainties, perturbation of navigational parameters, and forward modelling of electric field amplitudes for a homogeneous and then a heterogeneous sub-seafloor conductivity model. Some navigational uncertainties are estimated from variations of direct measurements. Other navigational parameters required for inversion are derived from the measured quantities and their error is calculated by means of error propagation. Some navigational parameters show direct correlation with the measured electric fields. For example, the antenna dip correlates with the vertical electric field and the depth correlates with the horizontal electric field. For the perturbation study each standard deviation is added to the navigational parameters. Forward models are run for each perturbation. Amplitude deviations are summed in quadrature with the stacking error for a total, laterally varying, data error. The error estimation is repeated for a heterogeneous sub-seafloor model due to the large conductivity range (several orders of magnitude), which affects the forward model. The approach enables us to utilize data from several components (multiple electric fields, frequencies and receivers) in the inversion to constrain the final model and reduce ambiguity. The final model is geologically reasonable, in this case enabling the identification of conductive metal sulphide deposits on the seafloor.

Study on Deep Tow System

The importance of deep ocean surveying and monitoring is increasing because of the change of situation of energy and oceanic resources. We propose a deep tow system which consists of a launcher and a towed vehicle to achieve high speed towing and good depth and motion control of the vehicle. In this research, motion simulations of a full-scale system were carried out. The influence of the towing cable's length, towing speed and the launcher's weight on the submersion depth of the towed vehicle, the influence of motions of the mother-ship on motions of the towed vehicle, the influence of the mother-ship's turning radius on the towed vehicle's drop and motion control performances of the towed vehicle are shown.

Petrology, geochemistry, and Sr, Nd isotopes of mantle xenolith in Nghia Dan alkaline basalt (West Nghe An): implications for lithospheric mantle characteristics beneath the region

Petrology, geochemistry, and Sr, Nd isotopes of mantle xenolith in Nghia Dan alkaline basalt (West Nghe An): implications for lithospheric mantle characteristics beneath the region

Geochemistry of late miocene-pleistocene basalts in the Phu Quy island area (East Vietnam Sea): Implication for mantle source feature and melt generation

Geochemistry of late miocene-pleistocene basalts in the Phu Quy island area (East Vietnam Sea): Implication for mantle source feature and melt generation

深海曳航体システムに関する研究

The importance of deep ocean surveying and monitoring is increasing because of the change of situation of energy, oceanicresources and CCS (Carbon Capture and Storage) under the seabed. In recent years, AUVs (Autonomous Underwater Vehicles) have been operated for deep ocean scientific research. However, their long cruising is limited because of their battery performance. Although deep tow systems will solve this problem, the towing speed of current systems is not fast, and sizable motions are induced by the mother ship. We therefore propose a deep tow system which consists of a launcher and a towed vehicle to achieve high speed towing and good depth and motion control of the vehicle. Model experiments were carried out in a towing tank and simulated results were compared with the experimental ones. Interesting results of depth and motion control are shown in this paper.

선수파 중 AFRAMAX급 유조선의 부가저항에 대한 실험과 수치계산

When a ship sails in a seaway, the resistance on a ship increases due to incident waves and winds. The magnitude of added resistance amounts to about 15-30% of a calm-water resistance. An accurate prediction of added resistance in waves, therefore, is essential to evaluate the performance of a ship in a real sea state and to design an optimum hull form from the viewpoint of the International Maritime Organization (IMO) regulations such as Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). The present study considers added resistance problem of AFRAMAX-class tankers with the conventional bow and Ax-bow shapes. Added resistance due to waves is successfully calculated using 1) a three-dimensional time-domain seakeeping computations based on a Rankine panel method (three-dimensional panel) and 2) a commercial CFD program (STAR-CCM+). In the hydrodynamic computations of a three-dimensional panel method, geometric nonlinearity is accounted for in Froude-Krylov and restoring forces using simple wave corrections over exact wet hull surface of the tankers. Furthermore, a CFD program is applied by performing fully nonlinear computation without using an analytical formula for added resistance or empirical values for the viscous effect. Numerical computations are validated through four degree-of-freedom model-scale seakeeping experiments in regular head waves at the deep towing tank of Hyundai Heavy Industries.

Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349

AbstractCombined analyses of deep tow magnetic anomalies and International Ocean Discovery Program Expedition 349 cores show that initial seafloor spreading started around 33 Ma in the northeastern South China Sea (SCS), but varied slightly by 1–2 Myr along the northern continent‐ocean boundary (COB). A southward ridge jump of ∼20 km occurred around 23.6 Ma in the East Subbasin; this timing also slightly varied along the ridge and was coeval to the onset of seafloor spreading in the Southwest Subbasin, which propagated for about 400 km southwestward from ∼23.6 to ∼21.5 Ma. The terminal age of seafloor spreading is ∼15 Ma in the East Subbasin and ∼16 Ma in the Southwest Subbasin. The full spreading rate in the East Subbasin varied largely from ∼20 to ∼80 km/Myr, but mostly decreased with time except for the period between ∼26.0 Ma and the ridge jump (∼23.6 Ma), within which the rate was the fastest at ∼70 km/Myr on average. The spreading rates are not correlated, in most cases, to magnetic anomaly amplitudes that reflect basement magnetization contrasts. Shipboard magnetic measurements reveal at least one magnetic reversal in the top 100 m of basaltic layers, in addition to large vertical intensity variations. These complexities are caused by late‐stage lava flows that are magnetized in a different polarity from the primary basaltic layer emplaced during the main phase of crustal accretion. Deep tow magnetic modeling also reveals this smearing in basement magnetizations by incorporating a contamination coefficient of 0.5, which partly alleviates the problem of assuming a magnetic blocking model of constant thickness and uniform magnetization. The primary contribution to magnetic anomalies of the SCS is not in the top 100 m of the igneous basement.

A data processing method for MAPR hydrothermal plume turbidity data and its application in the Precious Stone Mountain hydrothermal field

Hydrothermal plume is an important constituent of seabed hydrothermal circulation and is also one of the characteristics of active hydrothermal vents. Portable Miniature Autonomous Plume Recorders (MAPR) attached to a towed deep-sea instrument was used to search for hydrothermal plumes and hydrothermal vents. We introduced the basic principle of MAPR based on deep towing technology to detect plumes, then analyzed the factors affecting the quality of the MAPR data and presented a data correction method for MAPR, including instrument location correction, noise reduction processing, system error elimination and seawater background reduction. Finally we applied the method to analyze MAPR data obtained during the Chinese DY115-21 cruise on R/V Dayang I in the “Precious Stone Mountain” hydrothermal field on the Galapagos Microplate. The results provided a better understanding of the distribution of the hydrothermal activity in this field, indicating the presence of a new hydrothermal vent.

Broadband marine seismic, how much difference does acquisition and or processing make? A case study from Southeast Asia

In this paper, we present a case study of a consistent, experimental offshore dataset in Southeast Asia. This data consists of a single boat pass of multiple cables at different depth configurations. The resultant sub lines were then processed with their appropriate deghosting methods and results compared. The key determinants of the eventual bandwidth of surface seismic data are the convolution of the source pulse with near surface effects (free surface source and receiver ghosts in the marine situation), the overall earth attenuation, and the level of additive environmental noise. Some of these effects can be modified by changes in the field acquisition geometry or, at least, deterministically compensated in processing. The noise level may constrain or limit the capacity of signal processing tools to compensate for the “field” effects. When evaluating the raw and processed data it is wise to use various types of analysis and displays. Simple seismic amplitude stack sections and associated spectra can be misleading. Spectral “split” plots and inversion of the seismic data are often more indicative of success. In marine seismic acquisition, the free-surface ghost effect is one factor that can strongly impact the data bandwidth dependant on the streamer and source depths. These are also easily adjusted in the survey design. Shallow towing favours the higher frequency response at the expense of low frequencies, whilst deeper towing favours the lower frequencies, at the expense of higher frequencies. Moreover, a deeper tow typically has lower levels of swell noise. At very low frequencies, the critical two octaves between two to eight Hz, we are presented with a “triple threat”; the level of ambient environmental noise rises, the “DC notch” strengthens, and the power output of airgun sources declines. This combination provides both the biggest challenge and the biggest opportunity for bandwidth expansion. METHOD AND RESULTS

Broadband Processing of Conventional and Deep Tow Marine Streamer Seismic Data

We have developed WiBand, a de-ghosting and broadband processing method that can be applied to conventional streamer data acquired with single component streamers. We review two case studies of WiB...

Zooplankton time series from the Strait of Georgia: Results from year-round sampling at deep water locations, 1990–2010

We have compiled and archived a large fraction of the zooplankton data collected from the Strait of Georgia during the past 50years. Although the full dataset is very heterogeneous and gappy, sampling since 1990 has been consistent and frequent enough to examine interannual variability of the full zooplankton community. In this paper we focus on deep tows at mid-Strait deep-water locations, where vertical-migratory zooplankton can be captured at all times of day and all seasons. Average zooplankton dryweight biomass is high (∼9gm−2) and varies seasonally between a winter minimum (∼4gm−2) and a broad late-spring to autumn maximum (10–11gm−2). Much of the biomass in all seasons consists of large crustaceans (copepods, euphausiids and amphipods with oceanic and subarctic zoogeographic affinities) that undergo strong diurnal or seasonal vertical migrations. Their interannual variability is very strong: about an order of magnitude within most zooplankton categories, and nearly two orders of magnitude for euphausiids, large copepods, and chaetognaths. Most (73%) of the interannual variability is accounted for by three principal components. The dominant mode (36%) is a low-frequency decadal fluctuation shared by most zooplankton taxa: declining from 1990 to 1995, increasing to a maximum ∼1999–2002, declining to a second minimum in 2005–2007, and then recovering to near-average levels by 2010. This zooplankton signal correlates positively with the North Pacific Gyre Oscillation (NPGO) climate index, negatively with temperature anomalies throughout the water column, and positively (but less consistently) with survival anomalies of Strait of Georgia salmon and herring. Proximal causal mechanisms are less certain, but probably include estuarine advective exchange with outer coast populations, and timing match–mismatch within the Strait.

Direct algorithms for steady-state solution of long slender marine structures

The steady state solution of long slender marine structures simply indicates the steady motion response to the excitation at top of the structure. It is very crucial especially for deep towing systems to find out how the towed body and towing cable work under certain towing speed. This paper has presented a direct algorithm using Runge-Kutta method for steady-state solution of long slender cylindrical structures and compared to the time iteration calculation; the direct algorithm spends much less time than the time-iteration scheme. Therefore, the direct algorithm proposed in this paper is quite efficient in providing credible reference for marine engineering applications.

The Development Status of Underwater Positioning and Navigation Technology Used on Deep Tow System

The methods of the geophysical navigation and acoustic navigation are outlined in this paper. And this paper focuses on the applications of acoustic positioning used on deep tow system. The advantages and disadvantages of three traditional acoustic positioning systems, especially for USBL system, are respectively summarized. Some typical products are listed to illuminate the performance and application of acoustic navigation system. And this paper pointed out the key technical problems to be solved and its development of underwater navigation. Combined acoustic navigation and integrated navigation will become a research hotspot.

Improved seismic inversion and reservoir description of the Ichthys gas-condensate field, Browse Basin, Western Australia

Seismic inversion has become a standard geophysical tool to enhance seismic resolution, predict the reservoir porosity distribution, and to discriminate between reservoir and non-reservoir pay zones. Conventional seismic data does not record the low frequencies necessary for inversion. To enable a complete bandwidth, low frequencies are modelled from well data and are typically interpolated throughout the volume using seismic velocities. This often causes the resultant porosity distribution calculated from the inverted P-impedance to be biased by the well data and the geometry of well locations. Dual-sensor GeoStreamer technology was used to acquire a regional multi-client 2D survey by PGS in 2008, including some lines over the Ichthys gas-condensate field in the Browse Basin. Dual-sensor streamer processing recovers a wider frequency bandwidth than conventional seismic. Receiver ghost removal combined with deep streamer towing simultaneously boosts both the low and high frequencies. The improved bandwidth enables a higher quality of velocity analysis, which further improves resolution throughout the section. Simultaneous inversion of the data validated the uplift of the low frequency data, and significantly reduced the bias towards well data for the low frequency model. The resultant P-impedance data demonstrated an excellent tie to well data. The dual-sensor technology promises to improve the description of the porosity distribution within our reservoir model.

William R. Normark (1943–2008)

William R. Normark passed away on 12 January 2008 at his home in Sunnyvale, Calif., after fighting cancer for nearly 8 years. Bill was born in Seattle, Wash., but grew up a proud resident of western Wyoming. He moved to the West Coast to attend Stanford University in California for his undergraduate studies and headed to the Scripps Institution of Oceanography in La Jolla, Calif., for his Ph.D. While at Scripps, he started his pioneering studies on submarine fans using the newly developed remotely operated vehicle (ROV) Deep Tow under Fred Spiess's guidance. There, he also met his bride‐to‐be, Dorothy Jean “D.J.” Detrich. After Bill received his Ph.D., he and D.J. spent 4 years at the University of Minnesota in Minneapolis before heading west again in 1974 where Bill began a distinguished career at the U.S. Geological Survey (USGS) in Menlo Park, Calif.