Vertical hydrophone cable acquisition and imaging on land

We acquired seismic data using a vertical hydrophone cable in a shallow, fluid‐filled borehole over the Blackfoot oil field in Alberta, Canada. The hydrophone data were recorded simultaneously with a surface seismic survey using dynamite sources. In addition, buried three‐component (3‐C) geophone data were acquired near the vertical cable. We observe that events on the hydrophone records are in phase with corresponding geophone data. Tube waves, which can be a problem on hydrophone data, are suppressed using a predictive deconvolution operator. Imaging, using the hydrophone data, results in a section that correlates well with a surface seismic image from vertical‐component geophone data. An anomaly, interpreted to be associated with the sand reservoir in the area, is evident on the hydrophone image (as well as on the surface seismic sections). The vertical hydrophone cable promises excellent imaging potential for land applications.

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Neogene-Quaternary seismic stratigraphy of the Llancanelo Lake Basin, Mendoza, Argentina

Andean geology ◽

10.5027/andgeov45n1-3026 ◽

2017 ◽

Vol 45 (1) ◽

pp. 35 ◽

Cited By ~ 3

Author(s):

Luciano Onnis ◽

Roberto Antonio Violante ◽

Ana Osella ◽

Matías De la Vega ◽

Alejandro Tassone ◽

...

Keyword(s):

Seismic Data ◽

Seismic Stratigraphy ◽

Seismic Survey ◽

Lake Basin ◽

Late Mesozoic ◽

The Andes ◽

Lake Region ◽

Volcanic Processes ◽

Seismic Sections ◽

Existing Data

A new shallow multichannel seismic survey was carried out in the Llancanelo Lake region (Southern Mendoza Province, Argentina), in order to complete and extend previously surveyed seismic sections. The new seismic data allowed to double the already existing data. The obtained information was correlated with seismic and stratigraphic data from the industry. In this way it was possible to depict the major Neogene-Quaternary sedimentary-volcanic sequences and the regional evolution of a tectonic-volcanic basin located in a key region at the eastern foot of the Andes cordillera. This research is settled on early studies that comprised seismic works reaching depths of 600-700 m as well as geoelectric and electromagnetic surveys reaching the uppermost 80-100 m of the sequences. The obtained results indicate the presence of three major sedimentary units separated by conspicuous seismic horizons SR1, SR2 and SR3, respectively considered as representing the late Mesozoic transition from marine to continental deposition, the beginning of the Cenozoic basaltic volcanism, and the change from dominantly sedimentary to dominantly volcanic processes at the base of the Quaternary. The resulting stratigraphic scheme reveals increasing volcanic (basaltic layers) intercalations with depth that accommodate to the geometry of the depocenter.

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The Role of Legacy Seismic in Enhancing the Image in the Current Seismic Data – Abu Dhabi: Case Study

10.2118/207734-ms ◽

2021 ◽

Author(s):

Ramy Elasrag ◽

Thuraya Al Ghafri ◽

Faaeza Al Katheer ◽

Yousuf Al-Aufi ◽

Ivica Mihaljevic ◽

...

Keyword(s):

Seismic Data ◽

Seismic Survey ◽

Surface Model ◽

Noise Attenuation ◽

Near Surface ◽

Velocity Models ◽

Multiple Attenuation ◽

Seismic Image ◽

Seismic Acquisition

Abstract Acquiring surface seismic data can be challenging in areas of intense human activities, due to presence of infrastructures (roads, houses, rigs), often leaving large gaps in the fold of coverage that can span over several kilometers. Modern interpolation algorithms can interpolate up to a certain extent, but quality of reconstructed seismic data diminishes as the acquisition gap increases. This is where vintage seismic acquisition can aid processing and imaging, especially if previous acquisition did not face the same surface obstacles. In this paper we will present how the legacy seismic survey has helped to fill in the data gaps of the new acquisition and produced improved seismic image. The new acquisition survey is part of the Mega 3D onshore effort undertaken by ADNOC, characterized by dense shot and receiver spacing with focus on full azimuth and broadband. Due to surface infrastructures, data could not be completely acquired leaving sizable gap in the target area. However, a legacy seismic acquisition undertaken in 2014 had access to such gap zones, as infrastructures were not present at the time. Legacy seismic data has been previously processed and imaged, however simple post-imaging merge would not be adequate as two datasets were processed using different workflows and imaging was done using different velocity models. In order to synchronize the two datasets, we have processed them in parallel. Data matching and merging were done before regularization. It has been regularized to radial geometry using 5D Matching Pursuit with Fourier Interpolation (MPFI). This has provided 12 well sampled azimuth sectors that went through surface consistent processing, multiple attenuation, and residual noise attenuation. Near surface model was built using data-driven image-based static (DIBS) while reflection tomography was used to build the anisotropic velocity model. Imaging was done using Pre-Stack Kirchhoff Depth Migration. Processing legacy survey from the beginning has helped to improve signal to noise ratio which assisted with data merging to not degrade the quality of the end image. Building one near surface model allowed both datasets to match well in time domain. Bringing datasets to the same level was an important condition before matching and merging. Amplitude and phase analysis have shown that both surveys are aligned quite well with minimal difference. Only the portion of the legacy survey that covers the gap was used in the regularization, allowing MPFI to reconstruct missing data. Regularized data went through surface multiple attenuation and further noise attenuation as preconditioning for migration. Final image that is created using both datasets has allowed target to be imaged better.

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Megaseismic section across the northeastern slope of the Arabian Plate, Iraq

GeoArabia ◽

10.2113/geoarabia110477 ◽

2006 ◽

Vol 11 (4) ◽

pp. 77-90 ◽

Cited By ~ 2

Author(s):

Sabah A.G Mohammed

Keyword(s):

Seismic Data ◽

Structural Features ◽

Oil Field ◽

Western Desert ◽

Arabian Plate ◽

Channel System ◽

Level Data ◽

Seismic Image ◽

Middle Carboniferous ◽

Seismic Lines

ABSTRACT A composite seismic image (Megaseismic Line 7) was constructed across Iraq using 16 pre-existing seismic lines that were recorded between 1975 and 1983. The image is the first of 15 megaseismic lines that will eventually form a rectilinear grid that covers Iraq. It is oriented in a SW-NE direction, and extends approximately 500 kilometers from the Iraq-Saudi Arabia border to the Iraq-Iran border. The seismic lines were recorded using a 48-channel system with either a vibroseis or dynamite source. The maximum offset varies from 2,400 to 5,000 meters. The seismic data was reprocessed using a common datum of 300 meters above sea level. Data quality is good where the source was dynamite and the terrain consists of gravel and sand surfaces; it is poor where vibroseis was used or/and the outcrops were carbonates. The final stacked section and Hilbert attributes (reflection amplitude and instantaneous phase) were displayed at different scales to determine the best perspective for interpretation. A total of 14 reflections, corresponding to Miocene to Permian horizons, were identified using synthetic seismograms from five wells. The horizons generally dip towards the northeast, except at the location of the Tel Ghazal oil field where syndepositional growth is inferred. Various seismic stratigraphic geometries, such as sigmoidal features, onlap, toplap and downlap, were identified and used to define disconformities and angular unconformities. The oldest two horizons that could be picked are from the tops of the Triassic Kurra Chine and Permian Chia Zairi formations. Below the oldest Permian reflection, the middle Carboniferous “Hercynian unconformity” was tentatively picked. The Paleozoic pre-Permian succession is not adequately imaged in the seismic data, nor is the crystalline basement seen. The seismic interpretation was compared to the profiles of the Bouguer gravity anomaly and the total magnetic field, and good correlations were established. The regional line helped identify several previously unknown structural features including the Ma’aniya Depression in the Western Desert, and two anticlinal structures: the first being within that depression and the second directly to the southwest of Tel Ghazal oil field.

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Locating faults in underground coal mines using high‐resolution seismic reflection techniques

Geophysics ◽

10.1190/1.1442619 ◽

1989 ◽

Vol 54 (12) ◽

pp. 1521-1527 ◽

Cited By ~ 15

Author(s):

Lawrence M. Gochioco ◽

Steven A. Cotten

Keyword(s):

High Resolution ◽

Seismic Data ◽

Seismic Reflection ◽

Coal Mines ◽

Seismic Source ◽

Seismic Survey ◽

Underground Coal Mines ◽

Vertical Displacements ◽

Seismic Sections ◽

Mine Development

A high‐resolution seismic reflection technique was used to locate faults in coal seams that were not visible on the surface and could only be observed in underground coal mines. An 8‐gauge buffalo gun, built by the research and development department of Consolidation Coal Company, was used as the seismic source. The coal seam at a depth of 700 ft produces a reflection with a predominant frequency of about 125 Hz. The high‐resolution seismic data permitted faults with vertical displacements of the same magnitude as the seam thickness to be detected at depths of several hundred feet beneath the surface. Several faults were detected and interpreted from the seismic sections, and the magnitudes of their displacement were estimated by matching the recorded seismic data to synthetic seismic data. Subsequent underground mine development in the study area confirmed two interpreted faults and their estimated displacements. Mining engineers were able to use the information provided by the seismic survey to plan an entry system through the fault zone so that less rock needed to be mined, resulting in a safer and more productive mine.

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Mid-crustal detachment beneath southern Timor-Leste: seismic evidence for Australian basement in the Timor collision complex (and implications for prospectivity)

10.29118/ipa21-g-98 ◽

2021 ◽

Author(s):

T. R. Charlton

Keyword(s):

Seismic Data ◽

Passive Margin ◽

Petroleum Exploration ◽

Seismic Survey ◽

Normal Faults ◽

Thrust Belt ◽

Collision Complex ◽

Fold And Thrust Belt ◽

Timor Leste ◽

Seismic Sections

Seismic data originally acquired over SW Timor-Leste in 1994 shows two consistent seismic reflectors mappable across the study area. The shallower ‘red’ reflector (0.4-1s twt) deepens southward, although with a block-faulted morphology. The normal faults cutting the red marker tend to merge downward into the deeper ‘blue’ marker horizon (0.5-2.8s twt), which also deepens southward. Drilling intersections in the Matai petroleum exploration wells demonstrate that the red marker horizon corresponds to the top of metamorphic basement (Lolotoi Complex), while the blue marker horizon has the geometry of a mid-crustal extensional detachment. We see no indications for thrusting on the seismic sections below the red marker horizon, consistent with studies of the Lolotoi Complex at outcrop. However, surficial geology over much of the seismic survey area comprises a thin-skinned fold and thrust belt, established in 8 wells to overlie the Lolotoi Complex. We interpret the fold and thrust belt as the primary expression of Neogene arc-continent collisional orogeny, while the Lolotoi Complex represents Australian continental basement underthrust beneath the collision complex. In the seismic data the basal décollement to the thrust belt dips southward beneath the synorogenic Suai Basin on the south coast of Timor, and presumably continues southward beneath the offshore fold and thrust belt, linking into the northward-dipping décollement that emerges at the Timor Trough deformation front. The same seismic dataset has been interpreted by Bucknill et al. (2019) in terms of emplacement of an Asian allochthon on top of an imbricated Australian passive margin succession. These authors further interpreted a subthrust anticlinal exploration prospect beneath the allochthon, which Timor Resources plan to drill in 2021. This well (Lafaek) will have enormous significance not only commercially, but potentially also in resolving the long-standing allochthon controversy in Timor: i.e., does the Lolotoi Complex represent ‘Australian’ or ‘Asian’ basement?

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The Seismic Interpretation for (X) Oil Field Depending on 3D Seismic Data of Nearby Oil Field, Southern Iraq

Journal of Petroleum Research and Studies ◽

10.52716/jprs.v11i4.562 ◽

2021 ◽

Vol 11 (4) ◽

pp. 36-50

Author(s):

Wessam Abdul Abbas Alhammod ◽

Ban Talib Aljizani

Keyword(s):

Seismic Data ◽

Velocity Model ◽

Oil Field ◽

Seismic Survey ◽

Rock Properties ◽

3D Seismic ◽

Water Contact ◽

The Time Domain ◽

Structural Closure ◽

Southern Iraq

This research focused on using seismic data to review the structure of the (X) Oil Field, located 40 km SW of Basrah, Southern Iraq. The study utilises a 3D seismic survey conducted during 2011-2012, covering the (Y) Oil Field 2 km to the west, and with partial coverage across (X), to map the Top Zubair reflector. Seismic rock properties analysis was conducted on key (X) Oil Field wells and used to tie the Top Zubair reflector on (X) Oil Field. The reflector was mapped within the time domain using DecisionSpace Software, and then converted to depth using a velocity model. The depth structure map was then compared to the original oil water contact (OOWC) across the fields to understand the potential structural closure of the Top Zubair reservoir in both fields.

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Pre and Post-Stack Imaging of 2D Seismic Data Using Time Migration for Ajeel Oil field, Central of Iraq

Iraqi Journal of Science ◽

10.24996/ijs.2019.60.10.12 ◽

2019 ◽

pp. 2186-2195

Author(s):

Fadhil Abdulabass Obaid ◽

Ali M. Al-Rahim

Keyword(s):

Frequency Analysis ◽

Seismic Data ◽

Signal To Noise Ratio ◽

Oil Field ◽

Seismic Survey ◽

Signal To Noise ◽

Final Time ◽

Time Frequency Analysis ◽

Time Frequency ◽

Time Migration

Kirchhoff Time migration was applied in Pre and Post-Stack for 2D seismic survey for line AJ-99N, that is located in Ajeel oilfield in Salah Al-Din Governorate, Central Iraq. The process follows several accurate steps to reach the final time migration stage. The results of applied time migration give an accurate image for the Ajeel anticline reservoir and to improve the signal to noise ratio. Pre-Stack shows a clearer image for the structure in the study area, and the time-frequency analysis insure the result.

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Coherent noise in marine seismic data

Geophysics ◽

10.1190/1.1441516 ◽

1983 ◽

Vol 48 (7) ◽

pp. 854-886 ◽

Cited By ~ 65

Author(s):

Ken Larner ◽

Ron Chambers ◽

Mai Yang ◽

Walt Lynn ◽

Willon Wai

Keyword(s):

Seismic Data ◽

Noise Suppression ◽

Seismic Source ◽

Coherent Noise ◽

Critical Data ◽

Predictive Deconvolution ◽

Scattered Energy ◽

Marine Seismic ◽

The Many ◽

Water Bottom

Despite significant advances in marine streamer design, seismic data are often plagued by coherent noise having approximately linear moveout across stacked sections. With an understanding of the characteristics that distinguish such noise from signal, we can decide which noise‐suppression techniques to use and at what stages to apply them in acquisition and processing. Three general mechanisms that might produce such noise patterns on stacked sections are examined: direct and trapped waves that propagate outward from the seismic source, cable motion caused by the tugging action of the boat and tail buoy, and scattered energy from irregularities in the water bottom and sub‐bottom. Depending upon the mechanism, entirely different noise patterns can be observed on shot profiles and common‐midpoint (CMP) gathers; these patterns can be diagnostic of the dominant mechanism in a given set of data. Field data from Canada and Alaska suggest that the dominant noise is from waves scattered within the shallow sub‐buttom. This type of noise, while not obvious on the shot records, is actually enhanced by CMP stacking. Moreover, this noise is not confined to marine data; it can be as strong as surface wave noise on stacked land seismic data as well. Of the many processing tools available, moveout filtering is best for suppressing the noise while preserving signal. Since the scattered noise does not exhibit a linear moveout pattern on CMP‐sorted gathers, moveout filtering must be applied either to traces within shot records and common‐receiver gathers or to stacked traces. Our data example demonstrates that although it is more costly, moveout filtering of the unstacked data is particularly effective because it conditions the data for the critical data‐dependent processing steps of predictive deconvolution and velocity analysis.

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Pitfalls and limitations in seismic attribute interpretation of tectonic features

Interpretation ◽

10.1190/int-2014-0122.1 ◽

2015 ◽

Vol 3 (1) ◽

pp. SB5-SB15 ◽

Cited By ~ 64

Author(s):

Kurt J. Marfurt ◽

Tiago M. Alves

Keyword(s):

Seismic Data ◽

Seismic Attributes ◽

Seismic Attribute ◽

3D Data ◽

Amplitude Data ◽

Seismic Sections ◽

Push Down ◽

Data Coherence ◽

Level Of Experience ◽

Tectonic Features

Seismic attributes are routinely used to accelerate and quantify the interpretation of tectonic features in 3D seismic data. Coherence (or variance) cubes delineate the edges of megablocks and faulted strata, curvature delineates folds and flexures, while spectral components delineate lateral changes in thickness and lithology. Seismic attributes are at their best in extracting subtle and easy to overlook features on high-quality seismic data. However, seismic attributes can also exacerbate otherwise subtle effects such as acquisition footprint and velocity pull-up/push-down, as well as small processing and velocity errors in seismic imaging. As a result, the chance that an interpreter will suffer a pitfall is inversely proportional to his or her experience. Interpreters with a history of making conventional maps from vertical seismic sections will have previously encountered problems associated with acquisition, processing, and imaging. Because they know that attributes are a direct measure of the seismic amplitude data, they are not surprised that such attributes “accurately” represent these familiar errors. Less experienced interpreters may encounter these errors for the first time. Regardless of their level of experience, all interpreters are faced with increasingly larger seismic data volumes in which seismic attributes become valuable tools that aid in mapping and communicating geologic features of interest to their colleagues. In terms of attributes, structural pitfalls fall into two general categories: false structures due to seismic noise and processing errors including velocity pull-up/push-down due to lateral variations in the overburden and errors made in attribute computation by not accounting for structural dip. We evaluate these errors using 3D data volumes and find areas where present-day attributes do not provide the images we want.

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