Seismic identification of a karstified reservoir in the Adriatic Sea

Geophysics ◽  
1990 ◽  
Vol 55 (12) ◽  
pp. 1639-1644 ◽  
Author(s):  
M. Mendes ◽  
W. Beydoun ◽  
J. M. Planchon ◽  
A. Tarantola
Keyword(s):  
Adriatic Sea ◽  
S Wave ◽  
Seismic Line ◽  
Maximum Information ◽  
Seismic Reflection Data ◽  
Prestack Migration ◽  
Hydrocarbon Reservoir ◽  
Reflection Data ◽  
Ratio Image ◽  
Well Data

In this study, an elastic prestack migration/inversion (M/I) scheme was applied to a 2-D seismic line collected in the Adriatic Sea. The objective was to use M/I images to describe a hydrocarbon reservoir, consisting of karstified, brine‐saturated limestones. The M/I technique offers the benefit of extracting maximum information from seismic reflection data to describe, and in some cases characterize, the reservoir target. M/I images are calibrated with well data and represent approximate changes in P- and S-wave impedances across the reservoir. Combining these two images yields a Poisson’s ratio image.

Migration‐based traveltime waveform inversion of 2-D simple structures: A synthetic example

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 845-860 ◽  
Author(s):  
François Clément ◽  
Guy Chavent ◽  
Susana Gómez
Keyword(s):  
Least Squares ◽  
Waveform Inversion ◽  
Domain Of Attraction ◽  
Optimization Methods ◽  
Data Sets ◽  
Seismic Reflection Data ◽  
Prestack Migration ◽  
Reflection Data ◽  
Full Wave ◽  
The Time Domain

Migration‐based traveltime (MBTT) formulation provides algorithms for automatically determining background velocities from full‐waveform surface seismic reflection data using local optimization methods. In particular, it addresses the difficulty of the nonconvexity of the least‐squares data misfit function. The method consists of parameterizing the reflectivity in the time domain through a migration step and providing a multiscale representation for the smooth background velocity. We present an implementation of the MBTT approach for a 2-D finite‐difference (FD) full‐wave acoustic model. Numerical analysis on a 2-D synthetic example shows the ability of the method to find much more reliable estimates of both long and short wavelengths of the velocity than the classical least‐squares approach, even when starting from very poor initial guesses. This enlargement of the domain of attraction for the global minima of the least‐squares misfit has a price: each evaluation of the new objective function requires, besides the usual FD full‐wave forward modeling, an additional full‐wave prestack migration. Hence, the FD implementation of the MBTT approach presented in this paper is expected to provide a useful tool for the inversion of data sets of moderate size.

scholarly journals Hydraulic fracturing in thick shale basins: problems in identifying faults in the Bowland and Weald Basins, UK

2016 ◽  
Author(s):  
David K. Smythe
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Reflection ◽  
Upper Jurassic ◽  
Normal Faults ◽  
Regulatory Regime ◽  
Seismic Line ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Unconventional Resource ◽  
The Uk

Abstract. North American shale basins differ from their European counterparts in that the latter are one to two orders of magnitude smaller in area, but correspondingly thicker, and are cut or bounded by normal faults penetrating from the shale to the surface. There is thus an inherent risk of groundwater resource contamination via these faults during or after unconventional resource appraisal and development. US shale exploration experience cannot simply be transferred to the UK. The Bowland Basin, with 1900 m of Lower Carboniferous shale, is in the vanguard of UK shale gas development. A vertical appraisal well to test the shale by hydraulic fracturing (fracking), the first such in the UK, triggered earthquakes. Re-interpretation of the 3D seismic reflection data, and independently the well casing deformation data, both show that the well was drilled through the earthquake fault, and did not avoid it, as concluded by the exploration operator. Faulting in this thick shale is evidently difficult to recognise. The Weald Basin is a shallower Upper Jurassic unconventional oil play with stratigraphic similarities to the Bakken play of the Williston Basin, USA. Two Weald licensees have drilled, or have applied to drill, horizontal appraisal wells based on inadequate 2D seismic reflection data coverage. I show, using the data from the one horizontal well drilled to date, that one operator failed identify two small but significant through-going normal faults. The other operator portrayed a seismic line as an example of fault-free structure, but faulting had been smeared out by reprocessing. The case histories presented show that: (1) UK shale exploration to date is characterised by a low degree of technical competence, and (2) regulation, which is divided between four separate authorities, is not up to the task. If UK shale is to be exploited safely: (1) more sophisticated seismic imaging methods need to be developed and applied to both basins, to identify faults in shale with throws as small as 4–5 m, and (2) the current lax and inadequate regulatory regime must be overhauled, unified, and tightened up.

Integrating S‐wave seismic‐reflection data and cone penetration test data using a multiangle multiscale approach

Geophysics ◽  
2004 ◽  
Vol 69 (2) ◽  
pp. 440-459 ◽  
Author(s):  
Ranajit Ghose ◽  
Jeroen Goudswaard
Keyword(s):  
Wave Velocity ◽  
Seismic Reflection ◽  
Multiscale Analysis ◽  
S Wave ◽  
Cone Penetration ◽  
Seismic Reflection Data ◽  
Cone Resistance ◽  
Reflection Seismic ◽  
Reflection Data

A cone penetration test (CPT) is the most common geotechnical testing method used to estimate in situ the strength properties of soil. Although CPT provides valuable information, this information is restricted to the location of the measurement. We propose a new concept to integrate shallow S‐wave reflection seismic data with CPT data in order to obtain laterally continuous subsoil information. In this vein, a valid quantitative means to relate seismic reflections to CPT data is a primary requirement. The approach proposed here is based on the characterization of the scaling behavior of the local fine‐scale S‐wave velocity information extracted from the seismic reflection data and the same behavior of the CPT cone resistance. The local velocity contrast information is extracted by linearized Zoeppritz inversion of the amplitude‐preserved prestack reflection data. We have formulated a multiscale analysis approach employing the continuous wavelet transform in order to quantitatively characterize the nature of change at an interface of the local S‐wave velocity contrast and the CPT cone resistance and to illuminate any relation between these two. The multiscale analysis estimates the singularity parameter α, which indicates the nature of the interfacial change. The application of our method to the field data has uncovered a striking relation between the nature of variation of the local S‐wave velocity contrast and that of CPT cone resistance; otherwise, such a relation was not visible. Detailed analyses of two extensive field datasets have shown that the lateral fine‐scale variation of soil strength, as seen by CPT cone resistance, has a close resemblance with the variation of the local S‐wave velocity function as seen by angle‐dependent reflection measurements. This leads to a unique possibility to integrate two very different in‐situ measurements—reflection seismic and CPT—providing laterally continuous detailed information of the soil layer boundaries.

scholarly journals Inversion tectonics: a brief petroleum industry perspective

2020 ◽  
Author(s):  
Gábor Tari ◽  
Didier Arbouille ◽  
Zsolt Schléder ◽  
Tamás Tóth
Keyword(s):  
Petroleum Industry ◽  
Structural Complexity ◽  
Source Rocks ◽  
Petroleum Exploration ◽  
Data Sets ◽  
Hydrocarbon Generation ◽  
Seismic Reflection Data ◽  
Reflection Seismic ◽  
Reflection Data ◽  
Well Data

Abstract. The concept of structural inversion was introduced in the early 1980s. By definition, an inversion structure forms when a pre-existing extensional (or transtensional) fault controlling a hangingwall basin containing a syn-rift or passive fill sequence subsequently undergoes compression (or transpression) producing partial (or total) extrusion of the basin fill. Inverted structures provide traps for petroleum exploration, typically four-way structural closures. As to the degree of inversion, based on large number of worldwide examples seen in various basins, the most preferred petroleum exploration targets are mild to moderate inversional structures, defined by the location of the null-points. In these instances, the closures have a relatively small vertical amplitude, but simple in a map-view sense and well imaged on seismic reflection data. Also, the closures typically cluster above the extensional depocentres which tend to contain source rocks providing petroleum charge during and after the inversion. Cases for strong or total inversion are generally not that common and typically are not considered as ideal exploration prospects, mostly due to breaching and seismic imaging challenges associated with the trap(s) formed early on in the process of inversion. Also, migration may become tortuous due to the structural complexity or the source rock units may be uplifted above the hydrocarbon generation window effectively terminating the charge once the inversion occurred. For any particular structure the evidence for inversion is typically provided by subsurface data sets such as reflection seismic and well data. However, in many cases the deeper segments of the structure are either poorly imaged by the seismic data and/or have not been penetrated by exploration wells. In these cases the interpretation of any given structure in terms of inversion has to rely on the regional understanding of the basin evolution with evidence for an early phase of substantial crustal extension by normal faulting.

Petroleum Prospectivity of the Tasman Frontier

2014 ◽  
Vol 54 (2) ◽  
pp. 520
Author(s):  
Francois Bache ◽  
Vaughan Stagpoole ◽  
Rupert Sutherland ◽  
Julien Collot ◽  
Pierrick Rouillard ◽  
...  
Keyword(s):  
Source Rock ◽  
New Caledonia ◽  
Source Rocks ◽  
Rock Composition ◽  
Seismic Reflection Data ◽  
Bottom Simulating Reflector ◽  
Reflection Data ◽  
Stratigraphic Framework ◽  
Well Data ◽  
The One

The Fairway Basin lies between Australia and New Caledonia in the northern Tasman Frontier area with water depths ranging from less than 1,000–2,400 m. This basin was formed in the mid-to-late Cretaceous during the eastern Gondwana breakup and since then has received detrital and pelagic sediments. It is known for its 70,000 km2 bottom simulating reflector, interpreted as one of the world’s largest gas hydrate layers or as a regional diagenetic front. The seismic reflection data shows sedimentary thicknesses (up to 4 km) and geometries capable of trapping hydrocarbons. The authors interpreted the seismic stratigraphy and available well data in terms of paleogeography and tectonic evolution. This work allowed the discovery of a deeply buried delta, probably of the same type as the deep-water Taranaki Delta. This stratigraphic framework is used to constrain multi-1D generation modelling and to test three main hypotheses of source rocks. The most likely scenario, similar to the one accepted for the Taranaki petroleum province, are a type-III and type-II source rocks intercalated in a Cretaceous prograding series. Another possible scenario is a source rock equivalent to the east Australian Walloon Formation and the occurrence of the marine source rock in the pre-rift sequence. Although, the large modelled volumes at this stage are speculative due to limited data on source rock composition, richness and distribution, as well as on the presence and quality of reservoir and seal, this study confirms the prospectivity of the Fairway Basin and the need for more data to further assess this basin.

Application of waveform tomography to marine seismic reflection data from the Queen Charlotte Basin of western Canada

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. B55-B70 ◽  
Author(s):  
E. M. Takam Takougang ◽  
A. J. Calvert
Keyword(s):  
Seismic Reflection ◽  
Field Data ◽  
Velocity Model ◽  
P Wave ◽  
Low Velocity ◽  
Seismic Line ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Sonic Log ◽  
Waveform Tomography

To obtain a higher resolution quantitative P-wave velocity model, 2D waveform tomography was applied to seismic reflection data from the Queen Charlotte sedimentary basin off the west coast of Canada. The forward modeling and inversion were implemented in the frequency domain using the visco-acoustic wave equation. Field data preconditioning consisted of f-k filtering, 2D amplitude scaling, shot-to-shot amplitude balancing, and time windowing. The field data were inverted between 7 and 13.66 Hz, with attenuation introduced for frequencies ≥ 10.5 Hz to improve the final velocity model; two different approaches to sampling the frequencies were evaluated. The limited maximum offset of the marine data (3770 m) and the relatively high starting frequency (7 Hz) were the main challenges encountered during the inversion. An inversion strategy that successively recovered shallow-to-deep structures was designed to mitigate these issues. The inclusion of later arrivals in the waveform tomography resulted in a velocity model that extends to a depth of approximately 1200 m, twice the maximum depth of ray coverage in the ray-based tomography. Overall, there is a good agreement between the velocity model and a sonic log from a well on the seismic line, as well as between modeled shot gathers and field data. Anomalous zones of low velocity in the model correspond to previously identified faults or their upward continuation into the shallow Pliocene section where they are not readily identifiable in the conventional migration.

Linearized inversion of multioffset seismic reflection data in the ω-k domain

Geophysics ◽  
1986 ◽  
Vol 51 (6) ◽  
pp. 1266-1276 ◽  
Author(s):  
Luc T. Ikelle ◽  
Jean Paul Diet ◽  
Albert Tarantola
Keyword(s):  
Reference Model ◽  
Three Dimensional ◽  
Real Data ◽  
Seismic Reflection Data ◽  
Compressional Waves ◽  
Prestack Migration ◽  
Reflection Data ◽  
Single Function ◽  
Reference Medium ◽  
Acoustic Approximation

In the acoustic approximation, the Earth is described using only density and bulk modulus. Assuming smooth density variations, reflections can be described using a single function—the velocity of compressional waves. If a reference model which is close enough to the actual Earth is known, the problem of estimating the medium velocity from the observed data can be linearized. Using a least‐squares formulation and working in the ω-k domain, the linearized inverse problem for a homogeneous reference medium can be solved by a noniterative algorithm which is economically competitive with prestack migration. Numerical tests with synthetic and real data demonstrate the feasibility and the numerical stability of the method. The numerical results compare well with those obtained by migration of unstacked data, although superior results will only be obtained when the physics of the problem (including elastic versus acoustic effects, three‐dimensional propagation, and accurate source estimation) will realistically be taken into account.

Improving Q estimates from seismic reflection data using well‐log‐based localized spectral correction

Geophysics ◽  
2004 ◽  
Vol 69 (6) ◽  
pp. 1521-1529 ◽  
Author(s):  
Chris L. Hackert ◽  
Jorge O. Parra
Keyword(s):  
Seismic Reflection ◽  
Synthetic Data ◽  
Correction Method ◽  
South Florida ◽  
Test Case ◽  
Well Log ◽  
Seismic Line ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Q Values

Most methods for deriving Q from surface‐seismic data depend on the spectral content of the reflection. The spectrum of the reflected wave may be affected by the presence of thin beds in the formation, which makes Q estimates less reliable. We incorporate a method for correcting the reflected spectrum to remove local thin‐bed effects into the Q‐versus‐offset (QVO) method for determining attenuation from seismic‐reflection data. By dividing the observed spectrum by the local spectrum of the known reflectivity sequence from a nearby well log, we obtain a spectrum more closely resembling that which would be produced by a single primary reflector. This operation, equivalent to deconvolution in the time domain, is demonstrated to be successful using synthetic data. As a test case, we also apply the correction method to QVO with a real seismic line over a south Florida site containing many thin sandstone and carbonate beds. When corrected spectra are used, there is significantly less variance in the estimated Q values, and fewer unphysical negative Q values are obtained. Based on this method, it appears that sediments at the Florida site have a Q near 33 that is roughly constant from 170‐ to 600‐m depth over the length of the line.

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