Seismic sedimentology study of braided river — A case study in He8 and Shan1 members of Permian, Sulige western region, Ordos Basin

The He8 and Shan1 members deposited by braided river are major pay zones of the Sulige western region, Ordos Basin. In these two members, the P-wave impedance ranges of gas-bearing reservoir and the surrounding lithologies are highly overlapped. The gas-bearing reservoir cannot be feasibly recognized by the conventional poststack seismic data. In addition, the seismic reflection of the Shan1 member showing mid-weak amplitude distributes discontinuously within the whole seismic survey, leading to difficulties in tracking seismic events and delineating the plane map of reservoir distribution. To solve the problems above, a seismic sedimentology study was conducted in the study area. First, the seismic reflection characterization of braided river was studied according to its sedimentary model. Also, the amplitude variation with offset (AVO) seismic data were used to identify gas-bearing reservoir because the Poisson’s ratios of gas-bearing reservoir and the surrounding rocks are distinctly different. The AVO attribute volume is therefore converted into the lithologic volume, which is useful for the subsequent lithologic interpretation work. The isochronous surface of the Shan1 member seismic reflection can be achieved with the aid of a stratal slicing technique. The practice indicates the feasibility of lithologic converting of the AVO attribute volume. The gas-bearing reservoir of the He8 and Shan1 members can be precisely predicted, and the evolutional history and plane-distribution character of the gas-bearing reservoir are clearly delineated by the stratal slices with isochronous significance.

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Near-surface glaciotectonic structures in the sediments of an overdeepened glacial valley revealed by a shallow 3D seismic survey

10.5194/egusphere-egu21-8195 ◽

2021 ◽

Author(s):

David Tanner ◽

Hermann Buness ◽

Thomas Burschil

Keyword(s):

Seismic Reflection ◽

P Wave ◽

Seismic Survey ◽

Small Scale ◽

Academic Press ◽

Near Surface ◽

Glacial Sediments ◽

Area Source ◽

Terminal Moraine ◽

Rhine Valley

Glaciotectonic structures commonly include thrusting and folding, often as multiphase deformation. Here we present the results of a small-scale 3-D P-wave seismic reflection survey of glacial sediments within an overdeepened glacial valley in which we recognise unusual folding structures in front of push-moraine. The study area is in the Tannwald Basin, in southern Germany, about 50 km north of Lake Constance, where the basin is part of the glacial overdeepened Rhine Valley. The basin was excavated out of Tertiary Molasse sediments during the Hosskirchian stage, and infilled by 200 m of Hosskirchian and Rissian glacioclastics (Dietmanns Fm.). After an unconformity in the Rissian, a ca. 7 m-thick till (matrix-supported diamicton) was deposited, followed by up to 30 m of Rissian/W&#252;rmian coarse gravels and minor diamictons (Illmensee Fm.). The terminal moraine of the last W&#252;rmian glaciation overlies these deposits to the SW, not 200 m away.We conducted a 3-D, 120 x 120 m&#178;, P-wave seismic reflection survey around a prospective borehole site in the study area. Source/receiver points and lines were spaced at 3 m and 9 m, respectively. A 10 s sweep of 20-200 Hz was excited by a small electrodynamic, wheelbarrow-borne vibrator twice at every of the 1004 realized shot positions. We recognised that the top layer of coarse gravel above the till is folded, but not in the conventional buckling sense, rather as cuspate-lobate folding. The fold axes are parallel to the terminal moraine front. The wavelength of the folding varies between 40 and 80 m, and the thickness of the folded layer is on average about 20 m. Cuspate-lobate folding is typical for deformation of layers of differing mechanical competence (after Ramsay and Huber 1987; &#181;1/&#181;2 less than 10), so this tell us something about the relative competence (or stiffness) of the till layer compared to the coarse clastics above. We also detected small thrust faults that are also parallel to the push-moraine, but these have very little offset and most of the deformation was achieved by folding.Ramsay, J.G. and Huber, M. I. (1987): The techniques of modern structural geology, vol. 2: Folds and fractures: Academic Press, London, 700 pp.

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Unconventional Reservoir characterization and Sensitive Attributes Determination: A Case Study of Eastern Sembar Formation, Lower Indus Basin, Pakistan

Geophysics ◽

10.1190/geo2018-0761.1 ◽

2020 ◽

pp. 1-67

Author(s):

Muhammad Abid ◽

Liping Niu ◽

Jiqiang Ma ◽

Jianhua Geng

Keyword(s):

Organic Matter ◽

Seismic Data ◽

Wave Impedance ◽

P Wave ◽

Indus Basin ◽

Brittleness Index ◽

Poor Correlation ◽

Unconventional Reservoir ◽

Geomechanical Properties ◽

Lower Indus Basin

The Sembar Shale formation in Lower Indus Basin Pakistan is thought to contain significant potential of unconventional resources; however, no detailed study has yet been carried out to quantify its potential. In conventional oil and gas exploration, reservoir rocks have been the main focus therefore, limited number of wells target the Sembar Formation. To explore its regional view, the seismic characterization of these shale is required. Generally, a poor correlation is generally observed between P-wave impedance and the reservoir and geomechanical properties of rocks, making it challenging to characterize them using seismic data. We present a workflow for characterizing the seismic derived unconventional prospect of the Sembar Shale using prestack seismic data along with well logs. The logging results of the two wells show that organic matter richness of well A is in high to very high values while, well B is in low to very low values. Considering the mineral composition and brittleness index evaluation the Sembar Shale in well A is brittle to less brittle in nature. The organic content, porosity, and brittleness index results in well A makes the Lower Cretaceous Sembar Formation favorable to be considered as a potential organic shale reservoir. Four sensitive attributes, derived through integration of the rock petrophysical, geochemical and geomechanical parameters, are correlated with P-wave impedance. The correlation of each sensitive attribute has been applied to characterize the Sembar Shale potential. These attributes are first-order indicators to depict organic matter, porosity and geomechanical properties. This attribute approach is further validated through rock physics modeling. The workflow presented in this study can be employed to assess unconventional reservoir potential of the Sembar Formation in other parts of the basin.

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Application of 3D seismic attributes to optimize the placement of horizontal wells within a tight gas sand reservoir, Ordos Basin, China

Geophysics ◽

10.1190/geo2015-0244.1 ◽

2016 ◽

Vol 81 (3) ◽

pp. B77-B86 ◽

Cited By ~ 6

Author(s):

Zhiguo Wang ◽

Jinghuai Gao ◽

Xiaolan Lei ◽

Xiaojie Cui ◽

Daxing Wang

Keyword(s):

Seismic Data ◽

Ordos Basin ◽

Horizontal Wells ◽

Tight Gas ◽

3D Seismic ◽

Seismic Attribute ◽

Horizontal Drilling ◽

The Ordos Basin ◽

Gas Bearing ◽

3D Seismic Data

The Lower Permian Xiashihezi Formation in the Ordos Basin, China, is a quartz-sandstone reservoir with low porosity and low permeability. We have acquired 3D seismic data and well data from 18 vertical and four horizontal wells to indicate the potential of seismic attribute analyses in locating seismic sweet spots for lateral placement of horizontal wells. Using the analytic wavelet transform with a Morse wavelet, the integration of high tuning spectral components, high sweetness and high spectral attenuation helped us to estimate the distribution of gas-bearing tight sands in the Xiashihezi Formation. Our results revealed that the principal target of horizontal drilling and production was gas-bearing massive point bars in the braided river delta setting of the Ordos Basin. The integrated workflow of the seismic attribute analysis contributes to the optimal horizontal well planning by mining and exposing critical geological information of a tight gas sand reservoir from within 3D seismic data.

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Seismic reflection constraints on upper crustal structures in the volcanic-covered central Nechako basin, British Columbia1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

Canadian Journal of Earth Sciences ◽

10.1139/e10-097 ◽

2011 ◽

Vol 48 (6) ◽

pp. 1021-1037 ◽

Cited By ~ 9

Author(s):

A.J. Calvert ◽

N.E. Hayward ◽

J.E. Spratt ◽

J.A. Craven

Keyword(s):

British Columbia ◽

Seismic Data ◽

Seismic Reflection ◽

Mountain Pine Beetle ◽

Volcanic Rocks ◽

Seismic Survey ◽

Volcanic Stratigraphy ◽

Exploration Risk ◽

Good Signal ◽

Lower Crustal

In 2008, a Vibroseis seismic reflection survey was acquired by Geoscience BC across the eastern part of the volcanic-covered Nechako basin in central British Columbia, where Cretaceous sedimentary rocks have been exhumed along a NNW trend. Good signal penetration through the volcanic cover is indicated by lower crustal reflections at 8–12 s, which were recorded by the entire seismic survey. Comparison of the 2008 seismic survey with data from a previous survey indicates that the lack of reflectivity in the earlier surveys is generally representative of the subsurface geology. The seismic data show that ∼1700 and ∼2900 m thick sub-basins are present at the northern and southern ends of this trend, but the intervening Cretaceous rocks are discontinuous and relatively thin. The creation of a passive-roof duplex by Campanian or later low-angle thrusting is inferred within the thickest Cretaceous strata, but elsewhere faulting is likely related to Eocene extension or transtension. Seismic reflections are also recorded from folded volcanic stratigraphy, the base of the surface volcanic rocks, an underlying volcaniclastic stratigraphy, and intrusions projecting into a Quaternary volcanic cone. Seismic interpretation is complemented by coincident audiofrequency magnetotelluric surveys, from which faulting is inferred at offsets in a regional conductor. No regionally extensive stratigraphy can be identified within the seismic data, and the central Nechako basin appears to be a complex network of small, deformed sub-basins, rather than a single large basin.

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Coal Seam Roof: Lithology and Influence on the Enrichment of Coalbed Methane

Earth Sciences Research Journal ◽

10.15446/esrj.v23n4.84394 ◽

2019 ◽

Vol 23 (4) ◽

pp. 359-364

Author(s):

Yunlan He ◽

Xikai Wang ◽

Hongjie Sun ◽

Zhenguo Xing ◽

Shan Chong ◽

...

Keyword(s):

Coal Seam ◽

Coalbed Methane ◽

Low Frequency ◽

Propagation Speed ◽

Wave Impedance ◽

P Wave ◽

Borehole Data ◽

Seismic Frequencies ◽

Argillaceous Siltstone ◽

Gas Bearing

To identify the lithology of coal seam roof and explore the influence of these roofs on the enrichment of coalbed methane, low-frequency rock petrophysics experiments, seismic analyses and gas-bearing trend analyses were performed. The results show that the sound wave propagation speed in rock at seismic frequencies was lower than that at ultrasound frequencies. Additionally, the P-wave velocities of gritstone, fine sandstone, argillaceous siltstone and mudstone were 1,651 m/s, 2,840 m/s, 3,191 m/s and 4,214 m/s, respectively. The surface properties of the coal seam roofs were extracted through 3D seismic wave impedance inversion. The theoretical P-wave impedance was calculated after the tested P-wave velocity was determined. By matching the theoretical P-wave impedance of the four types of rocks with that of the coal seam roofs, we identified the lithology of the roofs. By analyzing known borehole data, we found that the identified lithology was consistent with that revealed by the data. By comparing and analyzing the coal seam roof lithology and the gas-bearing trends in the study area, we discovered that the coal seam roof lithology was related to the enrichment of coalbed methane. In the study area, areas with high gas contents mainly coincided with roof zones composed of mudstone and argillaceous siltstone, and those with low gas contents were mainly associated with fine sandstone roof areas. Thus, highly compact areas of coal seam roof are favorable for the formation and preservation of coalbed methane.

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Prediction of reservoir sand in Miocene deltaic deposits in Denmark based on high-resolution seismic data

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/geusb.v13.4966 ◽

2007 ◽

Vol 13 ◽

pp. 17-20 ◽

Cited By ~ 4

Author(s):

Erik S. Rasmussen ◽

Thomas Vangkilde-Pedersen ◽

Peter Scharling

Keyword(s):

High Resolution ◽

Seismic Data ◽

Seismic Reflection ◽

Oil And Gas ◽

Lower Miocene ◽

Sequence Stratigraphic ◽

Deep Aquifers ◽

Gas Bearing

Intense investigations of deep aquifers in Jylland, western Denmark, during the last seven years have resulted in de tailed mapping of Miocene sand-rich deposits laid down in fluvial channels, delta lobes, shoreface and spit complexes (Fig. 1; Rasmussen 2004). Detailed sedimentological and paly nol ogical studies of outcrops and cores, and interpretation of high-resolution seismic data, have resulted in a well-founded sequence-stratigraphic and lithostratigraphic scheme (Fig. 1) suitable for prediction of the distribution of sand. The Miocene succession onshore Denmark is divided into three sand-rich deltaic units: the Ribe and Bastrup sands and the Odderup Formation (Fig. 2). Prodeltaic clayey deposits of the Vejle Fjord and Arnum Formations interfinger with the sand-rich deposits. Most of the middle and upper Mio- cene in Denmark is composed of clayey sediments referred to the Hodde and Gram Formations (Fig. 2). This paper presents examples of seismic reflection patterns that have proved to correlate with sand-rich deposits from lower Miocene deltaic deposits and that could be applied in future exploration for aquifers and as analogues for oil- and gas-bearing sands in wave-dominated deltas.

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PROBLEM OF DETECTING NON-STRUCTURAL OIL-AND-GAS BEARING FEATURES ACCORDING TO SEISMIC DATA

GEOLOGY AND MINERAL RESOURCES OF SIBERIA ◽

10.20403/2078-0575-2020-4-63-72 ◽

2020 ◽

pp. 63-72

Author(s):

S. N. Smolin ◽

◽

G. M. Mitrofanov ◽

◽

...

Keyword(s):

Seismic Data ◽

Oil And Gas ◽

Survey Methods ◽

Sedimentary Rocks ◽

Practical Experience ◽

Seismic Survey ◽

Frequency Dependent ◽

Filtration Method ◽

Reflected Waves ◽

Gas Bearing

In sedimentary rocks, zones of excessive fissuring are often superimposed on porous and cavernous reservoir types, creating and complicating traps of non-structural hydrocarbons. Traps of this kind are hard to find and usually not detectable with standard CDP seismic survey methods. Non-standard approaches are needed in the implementation of their successful forecast. For this it is possible to use the properties of both scattered and specular reflected waves, on the basis of which a number of unique techniques have been created. In particular, these include the Prony filtration method, that allows for the frequency-dependent analysis of the wavefield, on the basis of which it is possible to successfully predict oil-and-gas bearing features of any complexity. The article provides an example of application of the Prony filtration method from the practical experience of the authors.

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Preconditioning point-source/point-receiver high-density 3D seismic data for lacustrine shale characterization in a loess mountain area

Interpretation ◽

10.1190/int-2016-0107.1 ◽

2017 ◽

Vol 5 (2) ◽

pp. SF177-SF188 ◽

Cited By ~ 3

Author(s):

Wei Wang ◽

Xiangzeng Wang ◽

Hongliu Zeng ◽

Quansheng Liang

Keyword(s):

Data Quality ◽

Seismic Data ◽

Ordos Basin ◽

Seismic Inversion ◽

High Density ◽

Seismic Survey ◽

3D Seismic ◽

Noise Characteristics ◽

Lacustrine Shale ◽

3D Seismic Data

In the study area, southeast of Ordos Basin in China, thick lacustrine shale/mudstone strata have been developed in the Triassic Yanchang Formation. Aiming to study these source/reservoir rocks, a 3D full-azimuth, high-density seismic survey was acquired. However, the surface in this region is covered by a thick loess layer, leading to seismic challenges such as complicated interferences and serious absorption of high frequencies. Despite a specially targeted seismic processing workflow, the prestack Kirchhoff time-migrated seismic data were still contaminated by severe noise, hindering seismic inversion and geologic interpretation. By taking account of the particular data quality and noise characteristics, we have developed a cascade workflow including three major methods to condition the poststack 3D seismic data. First, we removed the sticky coherent noise by a local pseudo [Formula: see text]-[Formula: see text]-[Formula: see text] Cadzow filtering. Then, we diminished the random noise by a structure-oriented filtering. Finally, we extended the frequency bandwidth with a spectral-balancing method based on the continuous wavelet transform. The data quality was improved after each of these steps through the proposed workflow. Compared with the original data, the conditioned final data show improved interpretability of the shale targets through geometric attribute analysis and depositional interpretation.

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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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3D seismic imaging of the Alpine Fault and the glacial valley at Whataroa, New Zealand

10.5194/egusphere-egu21-9743 ◽

2021 ◽

Author(s):

Vera Lay ◽

Stefan Buske ◽

Franz Kleine ◽

John Townend ◽

Richard Kellett ◽

...

Keyword(s):

New Zealand ◽

Fault Zone ◽

Seismic Data ◽

Seismic Imaging ◽

P Wave ◽

Seismic Survey ◽

Fault System ◽

3D Seismic ◽

Alpine Fault ◽

Drill Site

The Alpine Fault at the West Coast of the South Island (New Zealand) is a major plate boundary that is expected to rupture in the next 50 years, likely as a magnitude 8 earthquake. The Deep Fault Drilling Project (DFDP) aimed to deliver insight into the geological structure of this fault zone and its evolution by drilling and sampling the Alpine Fault at depth. Here we present results from a seismic survey around the DFDP-2 drill site in the Whataroa Valley where the drillhole almost reached the fault plane. This unique 3D seismic survey includes several 2D lines and a 3D array at the surface as well as borehole recordings. Within the borehole, the unique option to compare two measurement systems is used: conventional three-component borehole geophones and a fibre optic cable (heterodyne Distributed Vibration Sensing system (hDVS)). Both systems show coherent signals but only the hDVS system allowed a recording along the complete length of the borehole.Despite the challenging conditions for seismic imaging within a glacial valley filled with sediments and steeply dipping valley flanks, several structures related to the valley itself as well as the tectonic fault system are imaged. The pre-processing of the seismic data also includes wavefield separation for the zero-offset borehole data. Seismic images are obtained by prestack depth migration approaches.Within the glacial valley, particularly steep valley flanks are imaged directly and correlate well with results from the P-wave velocity model obtained by first arrival travel-time tomography. Additionally, a glacially over-deepened trough with nearly horizontally layered sediments is identified about 0.5 km south of the DFDP-2B borehole.With regard to the expected Alpine fault zone, a set of several reflectors dipping 40-56&#176; to the southeast are identified in a ~600 m wide zone between depths of 0.2 and 1.2 km that is interpreted to be the minimum extent of the damage zone. Different approaches image one distinct reflector dipping at 40&#176;, which is interpreted to be the main Alpine Fault reflector. This reflector is only ~100 m ahead from the lower end of the borehole. At shallower depths (z<0.5 km), additional reflectors are identified as fault segments and generally have steeper dips up to 56&#176;. About 1 km south of the drill site, a major fault is identified at a depth of 0.1-0.5 km that might be caused by the regional tectonics interacting with local valley structures. A good correlation is observed among the separate seismic data sets and with geological results such as the borehole stratigraphy and the expected surface trace of the fault.In conclusion, several structural details of the fault zone and its environment are seismically imaged and show the complexity of the Alpine Fault at the Whataroa Valley. Thus, a detailed seismic characterization clarifies the subsurface structures, which is crucial to understand the transpressive fault&#8217;s tectonic processes.

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