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Case Studies/Technical Talks
Geotrace's technical capabilities are often showcased in case studies, presentations at trade shows or regional meetings. The most recent technical papers can be accessed below; earlier information appears in the Archives.
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 Bandwidth Extension (Webcast - presented at Canadian Society of Exploration Geophysicists, March 9, 2010)
Prestack inversion was performed on a 3D dataset over a North American carbonate play. The PSTM gathers were conditioned and then Bandwidth Extension (BE) was performed on the data extending the bandwidth from less than 2 octaves to more than 3.5 octaves. After initially inverting to Vp, Vs and density other rock properties were derived including Poisson's ratio and Young's, bulk and shear moduli. Results were cross plotted and geobodies built corresponding to the best reservoir rock.
Drilling results pre- and post-inversion will be discussed. |
 New Inversion Methodology Improves Tie Lines Matches on 2D Surveys (presented at SEG, Houston, Texas, October 25-30, 2009)
One of the main challenges of dealing with 2D seismic surveys is to tie all the lines in a consistent manner. In this paper we present a new way of resolving the mistie of 2D data in a survey by casting the problem as a global inversion problem capable of producing an optimal set of match filters capable of minimizing (globally) the mismatch at the tie points of the 2D lines across the survey.
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How Does Seismic Data Quality Influence Pore Pressure Estimation and Interpretation? (presented at SEG, Houston, Texas, October 25-30, 2009)
Understanding formation pore pressure distribution is critical not only for the seal integrity and hydrocarbon accumulation column height evaluation of a prospect, but also for the drilling plan and hazard prevention of a well in today’s competitive exploration and production environment. There are two main approaches for pore pressure estimation: geological, using basin modeling and geophysical, using seismic velocity. In this paper, seismic velocity was used for pore pressure estimation. The impact of the input data quality in terms of signal-to-noise ratio (SNR) and frequency bandwidth on the accuracy of seismic velocity analysis and, ultimately, the reliability of pore pressure estimation were reviewed at selected milestone processing steps that were used to enhance the prestack time migrated (PSTM) seismic data. It was shown that the prestack data quality in terms of signal-to-noise ratio (SNR) and resolution can significantly affect velocity analysis and the quality of pore pressure estimation when the results are compared to known geophysical, geological, and engineering data. Finally, pore pressure and its related data were used for seal integrity assessment in prospect evaluation and multiple pressure attributes with predicted lithology from inversion were integrated for well design and hazard prevention in drilling with much less uncertainty.
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High Resolution Interpretation in the Llanos Basin, Colombia (presented at SBGf, Salvador, Brazil, August 24-28, 2009)
A case study is presented where the need to increase the resolution was paramount to the ability to interpret thin beds and their lateral terminations and small faulting. The purpose of this paper is to demonstrate how the application of a novel bandwidth extension technique (Smith et.al. First Break volume 26, June 2008) based on the continuous wavelet transform and the theory of harmonics made this possible. The higher resolution seismic data generated is of much higher quality and fidelity allowing for a better and more reliable interpretation.
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Bandwidth extension using harmonics (presented at SBGf, Salvador, Brazil, August 24-28, 2009
We show a new method of seismic resolution improvement using the Continuous Wavelet Transform (CWT). Using the CWT and the available bandwidth in the seismic, the phase and amplitude spectra of harmonics and sub-harmonics can be computed. These harmonic and sub-harmonic frequencies are then convolved onto the input data. Only frequencies for reflectivity that is above the ambient noise level in the CWT domain is added to the seismic wavelet. This process broadens the bandwidth of the signal which increases the resolution of the seismic data. |
Model-based PP-PS Joint Inversion - A Sensitivity Study on Method, Input Data Type, Initial Model and Noise Level (Presented at EAGE, June 2009)
We investigate two model-based prestack inversion methods: Simulated Annealing (SA) and Nonlinear Conjugate Gradient (CG) to simultaneously invert PP and PS prestack seismic data to three petroelastic parameters: Vp,Vs,and density. To properly test the methods and evaluate the results, various responses of a six-layer synthetic model with different parameters are computed is used as the input for inversion. The test procedure is designed to evaluate the impact of three key factors in a normal inversion workflow for these two inversion methods: (1) input data type, i.e., PP only, PS only or PP-PS jointly, (2) signal-to-noise ratio, and (3) initial model, In addition, we review the computation performance between two methods. From this controlled test environment we observe that (a) PP-PS joint inversion is more robust than the inversion of PP only or PS only, (b) both SA and CG are not greatly influenced by random noises, (c) SA method is less sensitive to the initial model than CG, (d) the inversion results of CG and SA are comparable but SA has an edge due to its global optimization, and (e) CG is much faster than SA in terms of computation not the result. |
Extending seismic bandwidth using the continuous wavelet transform (First Break, June 2008)
Resolution is the ability to identify individual features or details in a given image. By the 3D nature of seismic data, seismic resolution involves both vertical (temporal) and horizontal (spatial) resolution. Temporal resolution is a function of the frequency content of a given signal. Achieving optimal thin bed resolution requires a broadband spectrum. Since most seismic is very band-limited it is desirable to extend the bandwidth of the data in a manner that is both verifiable and consistent with the geology. |
High
Density High Resolution Seal Capacity and Pore Pressure Prediction
from 3D Seismic Data (Presented at EAGE, June 2007)
The estimated cost associated with geopressure problems can
easily reach US$9 billion a year for the oil and gas industry.
In recent years, with the increase of day rate for drilling
rigs, semis and ships, it is more critical than ever to understand
and quantify the formation pore pressure for assessing fluid
migration, seal capacity, drilling risk, and well planning
in order to high-grade the prospects, prevent drilling hazards
and reduce cost in various exploration and production activities. |
Nile
Delta Reservoir Case Study using a Novel Broad Band Pre-stack
Seismic Inversion to Rock Properties Technique (Presented
at EAGE, June 2007)
Exploration for hydrocarbons within an onshore concession
in the Nile Delta, Egypt has been ongoing for several years.
Despite the presence of clean sand reservoirs with a good
shale cap rock and four way closures, none of the wells drilled
so far have proved to be significant hydrocarbon producers.
A pre-stack seismic inversion to rock properties study was
therefore carried out to better understand the lithology in
the area and highlight potential reservoirs. A novel technique
was used to provide the broad bandwidth essential for a successful
inversion. This paper details the results of the project |
The Power
of 3D Visualization Using Pore Pressure Data (Upstream Technology,
May 2007)
The financial and environmental consequences of exploring
and producing in basins without a proper understanding of
3D pressure cell distribution can be disastrous, from increased
drilling costs, pollution and unrealized potential to a full-scale
blowout. The oil and gas industry estimates that the annual
cost associated with these problems reaches into the billions. |
Anisotropic Seismic Depth Migration to aid Tight Gas Prospectivity in the Mountain Front region of the Anadarko Basin (presented at SEG, Houston, Texas, October 25-30, 2009)
We describe a seismic depth imaging workflow that helps delineate tight gas prospectivity in the Mountain Front area of the Anadarko basin in the mid-continent United States. Our workflow involves extensive pre-processing of the seismic data, pre-stack Kirchhoff time and depth migration incorporating appropriate velocity models, and accounts for local anisotropy. Compared to previously available time migrated seismic data from the Mountain Front region, the resulting depth migrated seismic data from the application of our workflow shows substantial improvement in revealing the complex structural geology of the region. Improved clarity of the subsurface image, particularly in the deeper areas around the Mountain Front, leads to improved interpretability of the data, and hence puts us in an advantageous position to generate prospects which in turn helps make sound business decisions. Our workflow also has the potential to serve as an example for evaluating tight gas prospectivity in a similar tectonic environment.
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How Small is a Small 4D Signal - A Model Study for 4D Resolution (Presented at EAGE June, 2009)
With the maturation of 4D seismic, legacy 3D data are replaced by purposely-shot conventional 3D surveys with multiple monitors and short time separation to follow the impact of production. Furthermore, permanent seismic installation like has been proven technically successful and economically feasible under the right condition. Naturally with a shorter cycle between 4D surveys, the need to detect smaller 4D signals, amplitude changes, and time shifts has become more critical in order to improve the dynamic characterization of reservoirs. Since the motivation is to detect subtle 4D signals, in this paper we use the term 4D resolution to describe the detectability of 4D signals. If a small or subtle 4D signal can be detected by a seismic data of certain qualities, then such a seismic data is a high 4D resolution data. The idea is analogous to detecting thin beds with higher resolution data (Widess, 1973; Kallweit and Wood 1982). We test the impact of seismic bandwidth and non-repeatability and evaluate what kind of seismic characteristics a dataset would qualify it as a high 4D resolution dataset. Understanding these characteristics and qualifications would help us better design and process 4D seismic data and ensure the success of 4D application. |
Steep Dip Imaging Using an Orthogonal One-Way Wave Equation Migration (Presented at EAGE June, 2009)
An orthogonal one-way wave equation migration method is implemented to overcome the dip limitation of a one-way wave equation. Besides the conventional downward propagation of the source and receiver wave fields, an extra propagation along horizontal direction is introduced to eliminate the dip limitation. It is very efficient. The cost is about two times of the conventional one way wave equation migration. It doesn't require additional storage for the temporary files, and doesn't include any other overhead. The results show an impressive improvement of the steep dip image. |
Data Integration in a War Zone (Hart's E&P, October, 2007)
Finding, managing and integrating data can be a challenge in any environment. A team recently undertook this task in war-torn Iraq. |
Turning Ray Prestack Time Migration with Raytraced Offset-Dependent Velocities (Presented at SEG, September, 2007)
Conventional prestack time migration uses RMS velocities to map input data to output samples. Raytraced traveltimes may be converted to "velocities" at a suite of offset values, and used in place of traditional RMS velocities. This provides an implementation of curved ray migration that is not only more accurate than the 4th or 6th order approximations, but is also equivalent in computational time to the conventional straight ray (2nd order) approach to time migration. |
Improving performance and accuracy of 3D Kirchhoff migration (Presented at SEG, September, 2007)
Since 3D Prestack Kirchhoff Depth Migration (KPSDM) has become one of the leading imaging tools for hydrocarbon exploration, its accurate and precise handling of the kinematical and dynamical aspects of the wavefield have become center stage to the R&D efforts worldwide. In a separate paper in this proceeding by the same author, describe a modified antialiasing filter weight that corrects for amplitude artifacts observable in earlier designs. Here we continue the efforts of developing an efficient true amplitude migration algorithm by suggesting a simplificiation of the traditional filtering done during this process that will improve the performance and precision of the results. |
A
Review of some Powerful Noise Elimination Techniques for Land
Processing (Presented at EAGE, June 2007)
Raw seismic data are often dominated by noise. Both coherent
and incoherent noise are inherent to, and a pervasive problem
of, seismic data. To facilitate proper interpretation and
analysis of the relevant structure in the subsurface, the
elimination of this noise is essential. Noise attenuation
challenges have kept the oil and gas industry, and in particular
the seismic data processing professionals, busy for many years.
We have come a long way. However, the total elimination of
this noise remains an elusive goal. |
Tomographic Velocity
Inversion (Journal of Petroleum Technology, April 2007)
Geotrace has developed its MultiScale, MultiParameter Simultaneous
Velocity Inversion Tomography technology - MuST - to obtain
3D images of geologically complex areas. |
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