Ordovician glacial paleogeography: Integration of seismic spectral decomposition, well sedimentological data, and glacial modern analogs in the Murzuq Basin, Libya

2019 ◽  
Vol 7 (2) ◽  
pp. T383-T408 ◽  
Author(s):  
Francisco J. Bataller ◽  
Neil McDougall ◽  
Andrea Moscariello
Keyword(s):  
Seismic Data ◽  
Spectral Decomposition ◽  
Depositional Environments ◽  
Optimum Frequency ◽  
Data Set ◽  
Glacial Sediments ◽  
Depositional System ◽  
Significant Difference ◽  
Different Depths ◽  
Well Data

Ancient glacial sediments form major hydrocarbon plays in several parts of the world; most notably, North Africa, Latin America, and the Middle East. We have described a methodology for reconstructing broad-scale paleogeographies in just such a depositional system, using an extensive subsurface data set from the uppermost Ordovician glacial sediments of the Murzuq Basin of southwest Libya. Our workflow begins with the analysis of a large, high-quality 3D seismic data set, to understand the frequency content. Subsequently, optimum frequency bands are extracted, after applying spectral decomposition, and then recombined into an R (red) G (green) B (blue) blended cube. This volume is then treated as an image within which paleomorphological features can be distinguished and compared with modern glacial analogs. Mapping at different depths (time slices) of these features is then tied, by integration with core and image-log sedimentology, to specific depositional environments defined within the framework of a facies scheme developed using the well data and published outcrop studies. These depositional environments are extrapolated into areas with little or no well data using the spectral decomposition as a framework, always taking into account the significant difference in vertical resolution between the seismic data set and core-scale descriptions. The result of this methodology is a set of calibrated maps, at three different time depths (two-way time travel), indicating paleogeographic reconstructions of the glacial depositional environments in the study area and the evolution through time (at different depths/time slices 2D + 1) of these glacial settings.

Fracture detection via correlating P-wave amplitude variation with offset and azimuth analysis and well data in eastern central Saudi Arabia

2017 ◽  
Vol 5 (4) ◽  
pp. T531-T544
Author(s):  
Ali H. Al-Gawas ◽  
Abdullatif A. Al-Shuhail
Keyword(s):  
Saudi Arabia ◽  
Seismic Data ◽  
Production Data ◽  
Fracture Zones ◽  
Fracture Detection ◽  
Amplitude Variation ◽  
Data Set ◽  
Amplitude Variation With Offset ◽  
Well Data ◽  
Patch Geometry

The late Carboniferous clastic Unayzah-C in eastern central Saudi Arabia is a low-porosity, possibly fractured reservoir. Mapping the Unayzah-C is a challenge due to the low signal-to-noise ratio (S/N) and limited bandwidth in the conventional 3D seismic data. A related challenge is delineating and characterizing fracture zones within the Unayzah-C. Full-azimuth 3D broadband seismic data were acquired using point receivers, low-frequency sweeps down to 2 Hz, and 6 km patch geometry. The data indicate significant enhancement in continuity and resolution of the reflection data, leading to improved mapping of the Unayzah-C. Because the data set has a rectangular patch geometry with full inline offsets to 6000 m, using amplitude variation with offset and azimuth (AVOA) may be effective to delineate and characterize fracture zones within Unayzah-A and Unayzah-C. The study was undertaken to determine the improvement of wide-azimuth seismic data in fracture detection in clastic reservoirs. The results were validated with available well data including borehole images, well tests, and production data in the Unayzah-A. There are no production data or borehole images within the Unayzah-C. For validation, we had to refer to a comparison of alternative seismic fracture detection methods, mainly curvature and coherence. Anisotropy was found to be weak, which may be due to noise, clastic lithology, and heterogeneity of the reservoirs, in both reservoirs except for along the western steep flank of the study area. These may correspond to some north–south-trending faults suggested by circulation loss and borehole image data in a few wells. The orientation of the long axis of the anisotropy ellipses is northwest–southeast, and it is not in agreement with the north–south structural trend. No correlation was found among the curvature, coherence, and AVOA in Unayzah-A or Unayzah-C. Some possible explanations for the low correlation between the AVOA ellipticity and the natural fractures are a noisy data set, overburden anisotropy, heterogeneity, granulation seams, and deformation.

scholarly journals Zircon U-Pb ages of the Benom Complex: Implications for a Late Triassic uplift event in Central Peninsular Malaysia

2021 ◽  
Vol 72 ◽  
pp. 1-13
Author(s):  
Chee Meng Choong ◽  
◽  
Manuel Pubellier ◽  
Benjamin Sautter ◽  
Mirza Arshad Beg ◽  
...  
Keyword(s):  
Seismic Data ◽  
Spectral Decomposition ◽  
Input Data ◽  
Seismic Attributes ◽  
Structural Deformation ◽  
Quality Data ◽  
Late Triassic ◽  
Data Set ◽  
Decomposition Approach ◽  
Seismic Reflections

Over two decades, analysis of seismic attributes had been an integral part of seismic reflection interpretation. Seismic attributes are an influential assistance to seismic interpretation, delivering geoscientists with alternative images of structural (faults) and stratigraphic features (channels), which can be utilised as mechanisms to identify prospects, ascertain depositional environment and structural deformation history more rapidly even provide direct hydrocarbon indicators. The additional steps are obligatory to compute and interpret the attributes of faults and channels from seismic images, which are often sensitive to noise due to the characteristically computed as discontinuities of seismic reflections. Furthermore, on a conventional seismic profile or poor quality data, faults and channels are hard to visible. The current research review these geological structures through a case study of 3D seismic data from N-field in the viewpoint of Malay Basin. This study aimed to characterise the structure and stratigraphic features by using seismic attributes on the N-field below seismic resolution. Also, two different methods are proposed to improve seismic reflections, i.e., faults and channels that are hard to see on the conventional 3D data set. The first method, to detect faults in seismic data, which this paper employs the ant tracking attribute as a unique algorithm to be an advanced forwarding that introduces a new tool in the interpretation of fault. The effective implementation of ant tracking can be achieved when the output of other faults sensitive attributes are used as input data. In this work, the seismic data used are carefully conditioned using a signal. Chaos and variance that are sensitive to faults are applied to the seismic data set, and the output from these processes are used as input data that run the ant tracking attribute, which the faults were seen difficult to display on the raw seismic data. Meanwhile, for the second method, spectral decomposition was adopted to deliberate the way its method could be utilised to augment stratigraphic features (channels) of the N-field, where the channel is ultimately considered being one of the largest formations of the petroleum entrapment. The spectral decomposition analysis method is an alternative practice concentrated on processing S-transform that can offer better results. Spectral decomposition has been completed over the Pleistocene channels, and results propose that application of its methods directs to dependable implications. Respective channel in this area stands out more obviously within the specific frequency range. The thinner layer demonstrates higher amplitude reading at a higher frequency, and the thicker channel displays higher amplitude reading at a lower frequency. Implementation of spectral decomposition assists in deciding the channels that were placed within incised valleys and helps in recognising the orientation and the relative thickness of each channel. By doing this, the ant tracking attribute and spectral decomposition approach have generated the details of subsurface geologic features through attributes by obtaining enhanced reflections and channels and sharpened faults, respectively.

Building tilted transversely isotropic depth models using localized anisotropic tomography with well information

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. D27-D36 ◽  
Author(s):  
Andrey Bakulin ◽  
Marta Woodward ◽  
Dave Nichols ◽  
Konstantin Osypov ◽  
Olga Zdraveva
Keyword(s):  
Seismic Data ◽  
Model Building ◽  
Symmetry Axis ◽  
Transverse Isotropy ◽  
Synthetic Data ◽  
Rock Physics ◽  
Transversely Isotropic ◽  
Data Set ◽  
Anisotropic Models ◽  
Well Data

Tilted transverse isotropy (TTI) is increasingly recognized as a more geologically plausible description of anisotropy in sedimentary formations than vertical transverse isotropy (VTI). Although model-building approaches for VTI media are well understood, similar approaches for TTI media are in their infancy, even when the symmetry-axis direction is assumed known. We describe a tomographic approach that builds localized anisotropic models by jointly inverting surface-seismic and well data. We present a synthetic data example of anisotropic tomography applied to a layered TTI model with a symmetry-axis tilt of 45 degrees. We demonstrate three scenarios for constraining the solution. In the first scenario, velocity along the symmetry axis is known and tomography inverts for Thomsen’s [Formula: see text] and [Formula: see text] parame-ters. In the second scenario, tomography inverts for [Formula: see text], [Formula: see text], and velocity, using surface-seismic data and vertical check-shot traveltimes. In contrast to the VTI case, both these inversions are nonunique. To combat nonuniqueness, in the third scenario, we supplement check-shot and seismic data with the [Formula: see text] profile from an offset well. This allows recovery of the correct profiles for velocity along the symmetry axis and [Formula: see text]. We conclude that TTI is more ambiguous than VTI for model building. Additional well data or rock-physics assumptions may be required to constrain the tomography and arrive at geologically plausible TTI models. Furthermore, we demonstrate that VTI models with atypical Thomsen parameters can also fit the same joint seismic and check-shot data set. In this case, although imaging with VTI models can focus the TTI data and match vertical event depths, it leads to substantial lateral mispositioning of the reflections.

A seismic to simulation unconventional workflow using automated fault-detection attributes

2017 ◽  
Vol 5 (3) ◽  
pp. SJ41-SJ48 ◽  
Author(s):  
Jesse Lomask ◽  
Luisalic Hernandez ◽  
Veronica Liceras ◽  
Amit Kumar ◽  
Anna Khadeeva
Keyword(s):  
Seismic Data ◽  
Spatial Information ◽  
Spatial Location ◽  
Statistical Information ◽  
Natural Fracture ◽  
Fracture Networks ◽  
Data Set ◽  
Fault Indicator ◽  
Well Data ◽  
Additional Constraints

Natural fracture networks (NFNs) are used in unconventional reservoir simulators to model pressure and saturation changes in fractured rocks. These fracture networks are often derived from well data or well data combined with a variety of seismic-derived attributes to provide spatial information away from the wells. In cases in which there is a correlation between faults and fractures, the use of a fault indicator can provide additional constraints on the spatial location of the natural fractures. We use a fault attribute based on fault-oriented semblance as a secondary conditioner for the generation of NFNs. In addition, the distribution of automatically extracted faults from the fault-oriented semblance is used to augment the well-derived statistics for natural fracture generation. Without the benefit of this automated fault-extraction solution, to manually extract the fault-statistical information from the seismic data would be prohibitively tedious and time consuming. Finally, we determine, on a 3D field unconventional data set, that the use of fault-oriented semblance results in simulations that are significantly more geologically reasonable.

Multidomain analysis and wavefield separation of cross‐well seismic data

Geophysics ◽  
1994 ◽  
Vol 59 (1) ◽  
pp. 27-35 ◽  
Author(s):  
James W. Rector ◽  
Spyros K. Lazaratos ◽  
Jerry M. Harris ◽  
Mark Van Schaack
Keyword(s):  
Seismic Data ◽  
Common Source ◽  
Data Set ◽  
Traveltime Tomography ◽  
Wavefield Separation ◽  
Vsp Data ◽  
Well Data ◽  
Multiple Domains

While cross‐well traveltime tomography can be used to image the subsurface between well pairs, the use of cross‐well reflections is necessary to image at or below the base of wells, where the reservoir unit is often located. One approach to imaging cross‐well reflections is to treat each cross‐well gather as an offset VSP and perform wavefield separation of direct and reflected arrivals prior to stacking or migration. Wavefield separation of direct and reflected arrivals in VSP is accomplished by separating the total wavefield into up and downgoing components. Since reflectors can exist both above and below the borehole wavefield, separation of cross‐well data into up‐ and downgoing components does not achieve separation of direct and reflected arrivals. In our technique, we use moveout filters applied in the domain of common vertical source/receiver offset to extract reflected arrivals from the complex total wavefield of a cross‐well seismic data set. The multiple domains available for filtering and analysis make cross‐well data more akin to multifold surface seismic data, which can also be filtered in multiple domains, rather than typical VSP data, where there is only one domain (common source) in which to filter. Wavefield separation of cross‐well data is shown to be particularly effective against multiples when moveout filters are applied in common‐offset space.

Localized anisotropic tomography with well information in VTI media

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. D37-D45 ◽  
Author(s):  
Andrey Bakulin ◽  
Marta Woodward ◽  
Dave Nichols ◽  
Konstantin Osypov ◽  
Olga Zdraveva
Keyword(s):  
Vertical Velocity ◽  
Seismic Data ◽  
Model Building ◽  
Synthetic Data ◽  
Resolution Limit ◽  
Data Set ◽  
Anisotropic Models ◽  
Velocity Models ◽  
First Case ◽  
Well Data

We develop a concept of localized seismic grid tomography constrained by well information and apply it to building vertically transversely isotropic (VTI) velocity models in depth. The goal is to use a highly automated migration velocity analysis to build anisotropic models that combine optimal image focusing with accurate depth positioning in one step. We localize tomography to a limited volume around the well and jointly invert the surface seismic and well data. Well information is propagated into the local volume by using the method of preconditioning, whereby model updates are shaped to follow geologic layers with spatial smoothing constraints. We analyze our concept with a synthetic data example of anisotropic tomography applied to a 1D VTI model. We demonstrate four cases of introducing additionalinformation. In the first case, vertical velocity is assumed to be known, and the tomography inverts only for Thomsen’s [Formula: see text] and [Formula: see text] profiles using surface seismic data alone. In the second case, tomography simultaneously inverts for all three VTI parameters, including vertical velocity, using a joint data set that consists of surface seismic data and vertical check-shot traveltimes. In the third and fourth cases, sparse depth markers and walkaway vertical seismic profiling (VSP) are used, respectively, to supplement the seismic data. For all four examples, tomography reliably recovers the anisotropic velocity field up to a vertical resolution comparable to that of the well data. Even though walkaway VSP has the additional dimension of angle or offset, it offers no further increase in this resolution limit. Anisotropic tomography with well constraints has multiple advantages over other approaches and deserves a place in the portfolio of model-building tools.

Integrated interpretation of gravity, magnetic, seismic, and well data to image volcanic units for oil-gas exploration in the eastern Junggar Basin, northwest China

2020 ◽  
Vol 8 (4) ◽  
pp. SS113-SS127
Author(s):  
Kaijun Xu ◽  
Yaoguo Li
Keyword(s):  
Seismic Data ◽  
Volcanic Rocks ◽  
Junggar Basin ◽  
Magnetic Data ◽  
Magnetic Method ◽  
Data Set ◽  
Amplitude Inversion ◽  
Gravity And Magnetic ◽  
Integrated Interpretation ◽  
Well Data

We carried out a multigeophysical data joint interpretation to image volcanic units in an area where seismic imaging is difficult due to complicated and variable volcanic lithology. The gravity and magnetic methods can be effective in imaging the volcanic units because volcanic rocks are often strongly magnetic and have large density contrasts. Gravity and magnetic data have good lateral resolution, but they are faced with challenges in defining the depth extent. Although seismic data make for poor imaging in volcanic rocks, they can provide a reliable stratigraphic structure above volcanic rocks to improve the vertical resolution of the gravity and magnetic method. We have developed an integrated interpretation method that combines the advantages of seismic, gravity, magnetic, and well data to generate a 3D quasigeology model to image volcanic units. We first use seismic data to obtain the stratigraphic boundaries, and then we apply an anomaly stripping method based on a seismic-derived structure to extract residual gravity and magnetic anomaly produced by volcanic rocks. We further perform the 3D gravity and magnetic amplitude inversion to recover the distribution of the density and effective susceptibility. We perform geology differentiation using the inverted density and effective magnetic susceptibility to identify the spatial distribution of four groups of volcanic units. The results show that the integrated interpretation of multigeophysical data can significantly decrease the uncertainty associated with any single data set and yield more reliable imaging of lateral and vertical distribution of volcanic rocks.

Seismic attributes and analogs to characterize a large fold in the Taranaki Basin

2020 ◽  
Vol 8 (4) ◽  
pp. SR27-SR31
Author(s):  
Karelia La Marca Molina ◽  
Heather Bedle ◽  
Jerson Tellez
Keyword(s):  
New Zealand ◽  
Seismic Data ◽  
Large Scale ◽  
Seismic Attributes ◽  
Depositional Environments ◽  
Analysis Tool ◽  
Data Set ◽  
Reflection Seismic ◽  
Channel Belt ◽  
Large Channel

The Taranaki Basin lies in the western portion of New Zealand, onshore and offshore. It is a Cretaceous rift basin that is filled with up to approximately 10 km thick deposits from marine to deepwater depositional environments from the Cretaceous (approximately 93 ma) to the Neogene (approximately 15 ma). This basin underwent important tectonic events that resulted in large-scale features such as faults and folds and the deposition of turbidites such as channels and channel belts. These features easily are recognizable in seismic data. When analyzing the offshore 3D Pipeline data set, we recognized a peculiar fault-like feature with large-scale dimensions (approximately 15 km long and approximately 1 km wide) within the sequence. The alignment was perpendicular to the direction of deposition in the basin (southeast–northwest) as identified by previous studies and subparallel to the main structures in the area (southwest–northeast). We interpreted the seismic character of the funny-looking thing (FLT) likely as (1) a fault, (2) a fold, or (3) a large channel belt within the basin. We use seismic attributes such as coherence (Sobel filter), dip, cosine of phase, and curvature to characterize this feature geomorphologically. The geologic background of the area and analog settings aided in understanding and distinguishing the nature of this large structure. Monocline examples in seismic data are rare to find, and we want to show how to avoid misinterpretations. Geological feature: Fault-bend fold or large-amplitude fold (possibly monocline) Seismic appearance: Large, discontinuous, high-variance feature Alternative interpretations: Fault, fold Features with a similar appearance: Fault, fold, wide straight channel belt (time or horizon slice) Formation: Rift sequence of the Taranaki Basin Age: Eocene Location: Taranaki Basin, Western offshore New Zealand Seismic data: Provided by New Zealand Petroleum and Minerals Contributors: Karelia La Marca, Heather Bedle, Jerson Tellez; School of Geosciences; University of Oklahoma, Norman, OK, USA Analysis tool: 3D reflection seismic, geometric seismic attributes

scholarly journals Seismic Attributes For Enhancing Structural And Stratigraphic Features: Application To N-Field, Malay Basin, Malaysia

2021 ◽  
Vol 72 ◽  
pp. 101-111
Author(s):  
Nur Shafiqah Shahman ◽  
◽  
Norazif Anuar ◽  
Mohamed Elsaadany Mohamed Elsaadany ◽  
Deva Prasad Ghosh ◽  
...  
Keyword(s):  
Seismic Data ◽  
Spectral Decomposition ◽  
Input Data ◽  
Decomposition Analysis ◽  
Seismic Attributes ◽  
Structural Deformation ◽  
Quality Data ◽  
Data Set ◽  
Decomposition Approach ◽  
Seismic Reflections

Over two decades, analysis of seismic attributes had been an integral part of seismic reflection interpretation. Seismic attributes are an influential assistance to seismic interpretation, delivering geoscientists with alternative images of structural (faults) and stratigraphic features (channels), which can be utilised as mechanisms to identify prospects, ascertain depositional environment and structural deformation history more rapidly even provide direct hydrocarbon indicators. The additional steps are obligatory to compute and interpret the attributes of faults and channels from seismic images, which are often sensitive to noise due to the characteristically computed as discontinuities of seismic reflections. Furthermore, on a conventional seismic profile or poor quality data, faults and channels are hard to visible. The current research review these geological structures through a case study of 3D seismic data from N-field in the viewpoint of Malay Basin. This study aimed to characterise the structure and stratigraphic features by using seismic attributes on the N-field below seismic resolution. Also, two different methods are proposed to improve seismic reflections, i.e., faults and channels that are hard to see on the conventional 3D data set. The first method, to detect faults in seismic data, which this paper employs the ant tracking attribute as a unique algorithm to be an advanced forwarding that introduces a new tool in the interpretation of fault. The effective implementation of ant tracking can be achieved when the output of other faults sensitive attributes are used as input data. In this work, the seismic data used are carefully conditioned using a signal. Chaos and variance that are sensitive to faults are applied to the seismic data set, and the output from these processes are used as input data that run the ant tracking attribute, which the faults were seen difficult to display on the raw seismic data. Meanwhile, for the second method, spectral decomposition was adopted to deliberate the way its method could be utilised to augment stratigraphic features (channels) of the N-field, where the channel is ultimately considered being one of the largest formations of the petroleum entrapment. The spectral decomposition analysis method is an alternative practice concentrated on processing S-transform that can offer better results. Spectral decomposition has been completed over the Pleistocene channels, and results propose that application of its methods directs to dependable implications. Respective channel in this area stands out more obviously within the specific frequency range. The thinner layer demonstrates higher amplitude reading at a higher frequency, and the thicker channel displays higher amplitude reading at a lower frequency. Implementation of spectral decomposition assists in deciding the channels that were placed within incised valleys and helps in recognising the orientation and the relative thickness of each channel. By doing this, the ant tracking attribute and spectral decomposition approach have generated the details of subsurface geologic features through attributes by obtaining enhanced reflections and channels and sharpened faults, respectively.

scholarly journals Imaging of shallow structures around Küçükçekmece Lake in Istanbul land area with high resolution geophysical data.

2021 ◽  
Author(s):  
Hakan Alp ◽  
Okan Tezel ◽  
Denizhan Vardar ◽  
Yeliz İşcan Alp
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Seismic Data ◽  
Active Faults ◽  
Structural Features ◽  
Shelf Area ◽  
Land Area ◽  
Seismic Section ◽  
Data Set ◽  
Well Data

Abstract Küçükçekmece Lake and surrounding land area play an important role to understand the active tectonism of the southern land area of Istanbul. This study gives the results of a geophysical survey to understand the structural features of the study area. We collected geo-electrical data on the surrounding Küçükçekmece Lake. Totally 14 different VES values were inverted and evaluated variation of resistivity with depth. Additionally, the obtained apparent resistivity cross-sections for 3 profiles of VES points. All of them are interpreted considering geological well data from the study area and previous geophysical studies, which included especially high resolution shallow seismic data and chirp seismic data from the lake and shelf area in the Sea of Marmara close to the lake. The resistivity sections and inverted VES data show that faults cut the recent units and also cause resistivity changes in these units in the land area. These faults are consistent with the orientation of active faults observed from the seismic section on the lake and deforming the lake floor. This data set can be given as geophysical evidence for the existence of faults in the Istanbul land area.

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