Marine Seismic Surveys Research Articles

Synthesis of group compressed-air sources for marine seismics

The improvement of geological efficiency of marine seismic survey implies continuous improvement of the entire technological complex used in water areas. This is typically accomplished by using complex linear or spatial non-uniform compressed-air groups. In the development of such sources, in addition to solving a number of purely technical problems related to their placement on board the ship and safe operation, one of the most difficult tasks is to determine the initial requirements for selection of the main parameters of the group, such as the volumes of working chambers sources and geometry of their grouping, as well as other factors determining amplitude, time and frequency of emitted acoustic signals. This study considers the main principles of grouping the compressed-air sources for marine seismic survey. It is shown that the most important factors determining the choice of source parameters and specific research technology include the nature of geological tasks and seismic conditions, which primarily depend on the sea depth in the study area. A simple method of calculating the configuration of linear subgroups with fluctuation suppression is described, as well as examples of building linear and spatial groups based on them with pronounced directional properties are considered.

Formal Safety Assessment of a Marine Seismic Survey Vessel Operation, Incorporating Risk Matrix and Fault Tree Analysis

In maritime safety research, risk is assessed usually within the framework of formal safety assessment (FSA), which provides a formal and systematic methodology to improve the safety of lives, assets, and the environment. A bespoke application of FSA to mitigate accidents in marine seismic surveying is put forward in this paper, with the aim of improving the safety of seismic vessel operations, within the context of developing an economically viable strategy. The work herein takes a close look at the hazards in North Sea offshore seismic surveying, in order to identify critical risk factors, leading to marine seismic survey accidents. The risk factors leading to undesirable events are analysed both qualitatively and quantitatively. A risk matrix is introduced to screen the identified undesirable events. Further to the screening, Fault Tree Analysis (FTA) is presented to investigate and analyse the most critical risks of seismic survey operation, taking into account the lack of historical data. The obtained results show that man overboard (MOB) event is a major risk factor in marine seismic survey operation; lack of training on safe work practice, slippery deck as a result of rain, snow or water splash, sea state affecting human judgement, and poor communication are identified as the critical risk contributors to the MOB event. Consequently, the risk control options are focused on the critical risk contributors for decision-making. Lastly, suggestions for the introduction and development of the FSA methodology are highlighted for safer marine and offshore operations in general.

Analysis of Seismic Methods Used for Subsea Hydrocarbon Exploration

Subsea hydrocarbon exploration comprises detection and estimation of shape, depth, volume and other physical properties of hydrocarbon fields within the Earth’s subsurface layers. Marine seismic survey is a process that generally includes sending seismic waves into seabed and recording the intensity and travel time of reflected seismic waves to determine the subsurface features of the Earth. Different methods, equipment and techniques are used to conduct a survey, from sea surface seismic arrays to seabed local seismic station networks. In this paper different widely used seismic methods are presented, together with their advantages and drawbacks. Furthermore, new methods that are being developed and tested for future approach to more advanced and efficient seismic exploration are presented.

Letter to the Editor on: Design, modelling and imaging of marine seismic swarm surveys by E. Muyzert, Geophysical Prospecting66, 1535–1547

Geophysical ProspectingVolume 68, Issue 5 p. 1718-1720 Letter to the Editor Letter to the Editor on: Design, modelling and imaging of marine seismic swarm surveys by E. Muyzert, Geophysical Prospecting 66, 1535–1547 Gijs Vermeer, Corresponding Author gijs@3dsymsam.nl orcid.org/0000-0002-4340-3024 3DSymSam – Geophysical Advice, Frans Everstijnstraat 5, Voorschoten, 2251 RS The NetherlandsE-mail: gijs@3dsymsam.nlSearch for more papers by this authorKees Hornman, orcid.org/0000-0002-3964-2452 Retired, Voorburg, The NetherlandsSearch for more papers by this author Gijs Vermeer, Corresponding Author gijs@3dsymsam.nl orcid.org/0000-0002-4340-3024 3DSymSam – Geophysical Advice, Frans Everstijnstraat 5, Voorschoten, 2251 RS The NetherlandsE-mail: gijs@3dsymsam.nlSearch for more papers by this authorKees Hornman, orcid.org/0000-0002-3964-2452 Retired, Voorburg, The NetherlandsSearch for more papers by this author First published: 05 July 2019 https://doi.org/10.1111/1365-2478.12837Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume68, Issue5June 2020Pages 1718-1720 RelatedInformation

A Technique for Suppressing Bubble Oscillations from an Air Gun during Shallow-Water Marine Seismic Surveying

Non-explosive sources have become widespread. Along with electric spark and electrodynamic sources, which are used mainly in works on the upper part of a section, these include pneumatic sources. This type of source meets all the requirements for geophysical equipment. The main problem of such sources is the presence of intense pulsations and the long duration of the emitted signals, as well as the poor reliability of some clusters. The problem of pulsations during shallow water acquisitions is especially topical. The depth of shallow water does not allow one to extract a signature that is acceptable for the construction of an effective operator from the data due to the interference of pulsations from the direct wave with the bottom, while the suppression operator that is extracted from the theoretical signature often gives an unacceptable result. To solve bubble oscillation problems in shallow-water acquisition it is proposed to use combined information from bubble oscillations extracted from a direct wave, extracted from bottom reflections, waveform predicting deconvolution, and adaptive subtraction algorithms.

Reply and correction to Letter to the Editor “Design, modelling and imaging of marine seismic swarm surveys” by G. Vermeer and K. Hornman

Reply and correction to Letter to the Editor “Design, modelling and imaging of marine seismic swarm surveys” by G. Vermeer and K. Hornman

Direct hydrocarbon indicator (DHI) pitfall assessment in prospecting pliocene globigerina biogenic gas play in “X structure”, Madura Strait, East Java Basin

Direct Hydrocarbon Indicator (DHI) has a major role in the exploration of Pliocene globigerina biogenic gas play in Madura Strait, part of East Java Basin. This study aimed to assess the DHI pitfall within the X Structure which triggered by the drilling result of Well X3 (dry hole) that contradict with Well X1 that successfully discovered gas even though both wells targeted the same reservoir body and DHI features. Low gas saturation that decreases the compressional velocity (Vp) is predicted to be the main reason behind the DHI pitfall. Considering the limitation of qualitative interpretation to investigate the DHI pitfall, this research uses seismic quantitative interpretations, such as fluid substitution modeling, amplitude variations with offset (AVO), seismic inversion, and rock physics analysis to get a full understanding behind the DHI features in X Structure. The 2D marine seismic survey consists of 49 seismic lines and wells data were used in this research. Fluid substitution and Vp-Vs-ρ modelling confirm that the DHI pitfall is related to the non-economic gas saturation (Sg < 10 %) within the reservoir. As for the AVO and inversion analysis indicated that the gas water contact (GWC) level is around 1,389 ms (± 4,023 ft SSTVD). Rock physics analysis shows that the poor reservoir quality is predicted to be the reason behind the low gas accumulation within the reservoir. Several properties cut off for gas zone were derived such as, P-impedance < 5,700 gr/cc*m/s, Vp/Vs < 2.0, porosity > 40 %, dan VCL < 22 %. This research concluded that the seismic quantitative interpretations were successfully used to assess the DHI pitfall and to delineate the economic gas accumulation zone.

Seafloor elastic-parameter estimation based on a regularized AVO inversion method

Seafloor properties play important roles in both the civilian and the military domains. In this paper, we propose to use a regularization-based AVO (amplitude variation with offset) inversion method to estimate the elastic parameters of seafloor sediment along a seismic survey line. Conventional AVO research focuses mainly on the strata beneath seafloor sediment; accordingly, the AVO response of the interface between the seawater and seafloor sediment is typically ignored. Several studies on the estimation of seafloor elastic parameters have been published based on AVO theory. However, these earlier studies only consider one CRP (common reflection point) gather in the inversion process. When dealing with a long seismic survey with many CRPs, earlier methods involve clear random inversion errors along the survey line. To suppress the inversion errors, we try to regularize each of the elastic parameters along the seismic survey by a total-variation method. Synthetic tests demonstrate that the regularization-based method can effectively suppress the inversion errors along the seismic survey and yield much cleaner inversion results. Finally, we apply the regularization-based method to a real two-dimensional marine seismic survey and obtain satisfactory results, which further proves the efficacy of the method.

The CarbonNet Project – a case study of the use of marine assessments and advisory panels for stakeholder assurance

The CarbonNet project is investigating the feasibility of commercial-scale carbon capture and storage in Victoria. CarbonNet has identified a prospective storage site called Pelican, in the offshore Gippsland Basin in Bass Strait. CarbonNet undertook a 3D marine seismic survey (MSS) in 2018 as part of the appraisal program for Pelican. Environmental impacts and risks associated with the MSS were assessed in an Environment Plan accepted by Commonwealth and Victorian regulators. Underwater sound and its impact on the marine environment was a key issue raised by stakeholders. In response, CarbonNet put several initiatives in place to address concerns, including: undertaking marine habitat assessments before and after the MSS; and establishing an independent advisory panel to provide advice on the marine habitat assessments. The objectives of the habitat assessments were to confirm the abundance of key marine species before and after the MSS, and to determine whether any differences could be attributed to the MSS. To ensure that the habitat assessments were undertaken in a scientifically robust manner, an advisory panel was established consisting of representatives from regulatory agencies, academia and the fishing industry. This paper provides an overview of how CarbonNet used marine assessments and an advisory panel for stakeholder assurance.

CarbonNet progress towards a declaration of identified storage formation at the Pelican site with a new high-resolution 3D seismic dataset

The CarbonNet project is making the first ever application for a ‘declaration of an identified greenhouse gas storage formation’ (similar to a petroleum location) under the Offshore Petroleum and Greenhouse Gas Storage Act. Unlike a petroleum location, however, there is no ‘discovery’ involved in the application. Instead, a detailed technical assessment is required of the geological suitability for successful long-term storage of CO2. The key challenges to achieving a successful application relate to addressing ‘fundamental suitability determinants’ under the act and regulations. At Pelican (Gippsland Basin), a new high-resolution 3D seismic survey and over 10 nearby petroleum wells (and over 1500 basinal wells) supplement a crestal well drilled in 1967 that proved the seal and reservoir stratigraphy. The GCN18A 3D marine seismic survey has the highest spatial and frequency resolution to date in the Gippsland Basin. The survey was acquired in water depths from 15 to 35 m with a conventional eight-streamer seismic vessel, aided by LiDAR bathymetry. The 12.5 m bin size and pre-stack depth migration with multiple tomographic velocity iterations have produced an unprecedented high-quality image of the Latrobe Group reservoirs and sealing units. The 3D seismic data provides excellent structural definition of the Pelican Anticline, and the overlying Golden Beach-1A gas pool is excellent. Depositional detail of reservoir-seal pairs within the Latrobe Group has been resolved, allowing a confident assessment of petroleum gas in place and CO2 storage opportunities. The CarbonNet project is progressing with a low-risk storage concept at intra-formational level, as proven by trapped pools at nearby oil and gas fields. Laterally extensive intra-formational shales provide seals across the entire structure, providing pressure and fluid separation between the overlying shallow hydrocarbon gas pool and the deeper CO2 storage opportunity. CarbonNet is assessing this storage opportunity and progressing towards a ‘declaration of an identified greenhouse gas storage formation’.

Submesoscale Features and Turbulent Mixing of an Oblique Anticyclonic Eddy in the Gulf of Alaska Investigated by Marine Seismic Survey Data

AbstractMesoscale eddies are ubiquitous in the global ocean and can be captured by marine multichannel seismic surveys. In this study, a short‐lived anticyclonic eddy is characterized along the seismic line STEEP11 acquired on 30 September 2008 in northern Gulf of Alaska. Fine‐scale eddy stratification with alternative strong striae and weak layers is regarded as a typical eddy structure of the study region. The eddy center dips along a NW tilted axis of 1.9 ± 0.2° from the horizontal. Submesoscale structures including fronts and filaments coexist around the eddy periphery and dominate ~70% of the eddy volume. The estimated geostrophic current is asymmetric and ageostrophic components must play a significant role in balancing the eddy system. Nonlinearity of the eddy is strong as its rotation speed is much higher than its translation speed. We suggest that Ekman transport is probably responsible for the skewed shape with regards to the asymmetric geostrophic current and asymmetric submesoscale processes. Detailed turbulent diffusivities in and around the eddy are quantified, with an average level of 6.5 × 10−5 m2 s−1. The diapycnal diffusivities show an increasing pattern from the eddy center to the surrounding water. With the pervasive submesoscale processes as the transitional dynamics, a forward cascade of energy could be expected from the mesoscale eddy to the fine‐scale wave‐breaking and turbulence. The irregular vortex structure may reduce the structural stability, facilitate the energy conversion, and accelerate the eddy dissipation.

The effect of marine seismic surveys on the movement, abundance and community structure of demersal fish assemblages on the North West Shelf

In 2018, the Australian Institute of Marine Science (AIMS) and its partners, conducted an experiment to investigate the effect of exposure to a 3D seismic survey on demersal fishes. The experiment involved the use of a commercial seismic vessel equipped with a 2600 cubic inch air-gun array, sailing a racetrack pattern with eight operational (high exposure zone) and eight inactive (vessel control zone) sail lines, with a 500 m sequential line separation and ≈18 m shot point spacing. The high exposure and vessel control lines were separated by 35 km. Demersal fishes were observed in five sampling surveys over a 6-month period (three surveys before and two after exposure), using acoustic telemetry and stereo baited remote underwater videos systems (BRUVS). The telemetry component included the capture, tagging with acoustic transmitters and release of 387 red emperor (Lutjanus sebae) within two telemetry receiver arrays. These arrays, one in each zone, comprised 37 and 39 acoustic receivers over ≈32 km2, to record movements of tagged fish. The receivers provided near-continuous data on tag locations, and, hence, movement of fish in the area, until removal in December 2018. During each sampling survey, BRUVS were deployed at various distances from the area of the seismic survey. Study results are currently being finalised for presentation.

Technology GEONOD: Status and Prospects of Automation and Control

Seismic prospecting is one of the crucial components for an effective use of oil and gas fields on offshore. Since the costs of drilling a well on the shelf is hundreds of times more expensive than drilling a well on land, preliminary marine seismic exploration can help avoid unnecessary costs. High quality data of marine seismic surveys can only be obtained from bottom technologies: special bottom stations are lowered into the investigated area of the seabed. These bottom stations collecting direct and reflected acoustic signals (generated on the surface by an acoustic radiator) from the seabed. After all data is recorded, bottom stations are lifted to the surface, the recorded data is downloaded for subsequent interpretation. As a result, based on the obtained data, a 2D or 3D detailed map of the potential oil and gas deposits is complied. The resulting maps are used to determine the exact coordinates of the installation of drilling stations. The most common technology of marine seismic exploration is the use of bottom stations on a halyard rope. First development of this technology began in the 1970s and did not assume the means of automation work with bottom stations. All operations of removal and attachment of rope to station, diving and lifting stations, as well as a number of other operations were performed manually. Nowadays, there has not been any automation in working with stations on the halyard rope. In addition, the use of halyard rope has a number of disadvantages such as: Hooking of halyard rope for obstacles on the sea bottom; The breakage of the halyard rope; The need to have additional space on the vessel to store the halyard rope and all accessories, which leads to the use of larger vessels that can not operate at shallow depths; The halyard rope that is connected to the bottom stations generates a seismic noise, which degrades the quality of the received data; Impossible to conduct seismic prospecting in places with high shipping traffic. Developed over the past few years, a new Russian technology of marine seismic exploration GEONOD allows us easily solve many of mentioned problems. Many of these problems do not rise at all, since the GEONODE technology does not use halyards, and the work is carried out by the autonomous self-popup bottom stations (ASDS). In this paper a number of problems on applied mechanics and control in connection with technology GEONOD are considering.

Neotectonics of Southeast Jamaica Derived From Marine Seismic Surveys and Gravity Cores

AbstractTectonics in Southeast Jamaica is poorly understood, but the region may contain currently unknown faults that could generate large‐magnitude earthquakes. This study constrains tectonics in Southeast Jamaica by collecting and analyzing seismic and shallow sediment core data in and around Kingston Harbor. Seismic results reveal a previously unrecognized strike‐slip fault system that accommodates strain via a complex mix of compression and extension. The faults appear to be a blind extension of one major fault (i.e., The Bull Bay Strike‐Slip Fault) within the Enriquillo‐Plantain Garden Fault Zone. This fault system may represent significant hazards to Kingston Jamaica because the fault is active, located less than 5 km from the city, and a complete rupture of the fault could generate a Mw 5.8–6.9 earthquake. Our analyses highlight the need for continued paleoseismic studies, both onshore and offshore Jamaica.

Deep learning for low-frequency extrapolation from multioffset seismic data

Low-frequency seismic data are crucial for convergence of full-waveform inversion (FWI) to reliable subsurface properties. However, it is challenging to acquire field data with an appropriate signal-to-noise ratio in the low-frequency part of the spectrum. We have extrapolated low-frequency data from the respective higher frequency components of the seismic wavefield by using deep learning. Through wavenumber analysis, we find that extrapolation per shot gather has broader applicability than per-trace extrapolation. We numerically simulate marine seismic surveys for random subsurface models and train a deep convolutional neural network to derive a mapping between high and low frequencies. The trained network is then tested on sections from the BP and SEAM Phase I benchmark models. Our results indicate that we are able to recover 0.25 Hz data from the 2 to 4.5 Hz frequencies. We also determine that the extrapolated data are accurate enough for FWI application.

Short-range propagation characteristics of airgun pulses during marine seismic reflection surveys.

Marine seismic reflection surveys use airguns to generate repetitive high energy sound signals to image the structure of the seafloor. To better mitigate against the impact of airgun pulses on marine mammals, safety criteria are defined to ensure marine mammals are not exposed to high levels of acoustic energy. Accurate prediction of the sound received levels away from the airguns is required for conducting effective marine mammal monitoring. In this study, measurements by a horizontal hydrophone array towed by the R/V Marcus G. Langseth behind a seismic source array have been used to characterize short-range propagation of airgun pulses and predict the acoustic energy radiated from a seismic source. Data from the Cascadia Open-Access Seismic Transects seismic reflection survey are used to train a linear regression (LR) and a random forest (RF) model to estimate sound exposure levels (SELs) in short ranges from the airguns. Results show that the LR model does not account for all the variance in data. However, the RF model is able to estimate the SELs with a high coefficient of determination and a low mean squared error. Results from the LR model show that the rate at which SELs decrease in deep water does not match either of the cylindrical or spherical spreading models. Simulations are undertaken to understand this inconsistency as well as the effect of hydrophone group-averaging on data recorded by a seismic hydrophone array.

Low-frequency sound propagation in short ranges: A case where leaky modes can be observed

In an ocean waveguide, sound propagation can be modeled by the normal-modes theory. In a lossless ocean floor, the acoustic field is a finite sum of the normal modes that are trapped in the water column. These modes have real acoustic wave numbers and their equivalent rays are at angles less than the critical grazing angle. When attenuation is present in the ocean floor, the number of normal modes increases. Those additional modes, called “leaky modes,” have complex acoustic wave numbers, and their equivalent rays are steeper than the critical grazing angle. Since leaky modes attenuate in short ranges, they are not typically observable in measurements. In this presentation, I show that leaky modes can be observed on the data collected during marine seismic reflection surveys. Marine seismic reflection surveys are used to image the structure of the seafloor. They generate low-frequency signals from airguns and record the reflections off the seafloor up to a few kilometers from the source. I use simulations and experiments to characterize the short-range propagation of airgun pulses in shallow and deep water. The experimental data utilized in this study are from the COAST experiment conducted in the Northeast Pacific continental shelf.

Achieving consensus and convergence on a towed array passive acoustic monitoring standard for marine mammal monitoring

Towed passive acoustic monitoring (PAM) arrays from surface vessels has become a mature technology for marine mammal monitoring during marine seismic surveys. Multiple U.S. federal agencies have expressed a desire for consistent standards when implementing towed PAM. Two workshops involving academics, commercial PAM operators, and regulators have led to a comprehensive outline for an ASA towed array draft standard that covers requirements for initial operation planning, hardware, real-time monitoring and data acquisition, localization procedures, and post-operation validation. It does not cover operational mitigation decision criteria (such as power-down and/or shutdown of seismic airgun arrays), sound source verification, or how to initially establish the required detection range of the system. The standard’s fundamental goal is to reduce situations where background noise levels (arising from a variety of mechanisms) prevent effective PAM, and the dominant strategy employed is to standardize how acoustic measurements are logged, reported, and evaluated. Standardized plots would permit a non-technical supervisor or regulator to easily determine whether the PAM operation was self-noise limited under multiple operational circumstances. The approach taken here can serve as a template for future PAM standards for other deployment platforms [Work sponsored by BSSE and ONR Living Marine Resources Program.]

Taking into account the fluid saturation of bottom sediments in marine seismic survey problem

The problem of the numerical simulation of the seismic response from the marine bottom is considered. Acoustic equations are used for the description of the water dynamic behavior. Bottom sediments are described with the porous fluid-filled medium. The Dorovsky model is used. The algorithm for solving all hyperbolic equation systems with the grid-characteristic method was proposed. The distinctive feature of this approach is the ability to set explicitly necessary contact conditions between media with different rheology.

Influence of upscaling on identification of reservoir fluid properties using seismic-scale elastic constants

Elastic constants derived from seismic-scale measurements are often used to infer subsurface petrophysical properties based on rock-physics relationships established from either theoretic model or core-scale measurements. However, the spatial heterogeneity of rock physical properties at the local scale has a significant impact on this relation. To understand this problem, we built a scaled physical model comprised of artificial porous layers with different pore fluids. After conducting a two-dimensional marine seismic survey over the physical model, the physical modeling data ware then used to retrieve the elastic constants of the layered package. The seismic-scale results reveal that the identification of reservoir fluid properties is improved using elastic constants that is more sensitive to pore fluid properties. The results of numerical simulations show that Lamé moduli provide more insight into rock properties and pore-fluid contents than P-wave impedances, and that the relationship between the upscaled elastic constants and the effective fluid bulk moduli at the seismic scale is usually not perfectly preserved at the reservoir scale. To interpret seismic-scale elastic constants for petrophysical properties, the rock physics relationship need to be carefully calibrated. The findings will help us understand the upscaling of rock-physics transform, which will improve the accuracy of geological property predictions from seismic-scale elastic constants.