Case Studies/Technical Talks - Archive
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|Multi-dimensional high resolution imaging for accurate interpretation and reservoir characterization© (presented at SEG, Las Vegas, Nevada, USA, November 4-9, 2012)|
Most well planning, formation evaluation, reservoir engineering, and production management can ultimately be condensed to analyze and utilize the nature and spatial distribution of rock and fluid properties. This observation provides the motivation for this paper’s objectives to: (1) re-examine and broaden the meaning of high resolution, (2) review the impact of seismic resolution on imaging, and (3) assess the advantage of high resolution for interpretation and reservoir characterization. Multi-dimensional (nD) processing techniques are first shown to enhance the seismic image by increasing signal to noise ratio and filling in missing data due to acquisition irregularity. Then a novel resolution enhancement technique is applied to the data post-stack, post-migration, and pre-migration to exam its impact in terms of multidimensional (nD) resolution and its benefits for seismic imaging, interpretation, and reservoir characterization. It is concluded that the applications of nD processing and nD resolution enhancement can significantly improve the quality of interpretation and reservoir characterization.
|Resolution improvement and stratigraphic interpretation for the thin turbiditic sands in offshore Sabah, Malaysia - A pilot study© (presented at SEG, Las Vegas, Nevada, USA, November 4-9, 2012)|
The most difficult challenge in developing the deepwater
field, offshore Sabah, Malaysia for Petronas is to map the
thin turbidite sands characterized with significant thickness
and spatial variation due to the limitation of conventional
seismic resolution. Since the thin sand packages contain a
significant amount of hydrocarbon resource, it is essential
for oil companies to enhance the seismic resolution and
improve the 3D seismic image for detailed and accurate
interpretation and reservoir characterization in order to
design an optimal development and production plan. A
secondary challenge is to improve the image in the areas
affected by the existence of shallow gas and gas chimney.
Working with the client and their technical staffs, a unique
high resolution enhancement technique to extend the
seismic bandwidth was tested with an inline and a crossline
of a latest 3D dataset. One well with log data was used
for seismic and geology correlation and zero-phasing the
seismic data for post-stack application. A blind-well test
was also conducted by the client to verify the applicability
of the technique, the fitness of the geological correlation,
and the validity of the result. It was demonstrated that the
technique has significantly improved the usable seismic
bandwidth up to 2 octaves compared to the original input
data. In addition, the enhanced seismic data correlated quite
well with the blind well.
|Enhanced shallow water demultiple technology© (presented at SEG, Las Vegas, Nevada, USA, November 4-9, 2012)
Shallow Water Demultiple (SWD) is a very challenging problem for marine seismic data processing. In shallow water environments, water bottom reflections are recorded only on a few near offset traces because critical reflection angles are reached quickly. In very shallow water, water bottom reflections may disappear completely. This poses a limitation to any convolution based demultiple methods such as Surface Related Multiple Elimination (SRME) and SWD to predict first order multiple.
In this paper we propose a way to enhance these aforementioned methods by modeling the water bottom reflection and then adding it to the recorded seismic data. The modified data can then be used to predict first order multiple using SRME and/or SWD. We call these methods enhanced SRME and enhanced SWD, respectively. We shall also demonstrate that an optimal way to perform the multiple elimination is to cascade the enhanced SWD followed by SRME. We call this methodology Cascaded Enhanced Shallow Water Demultiple (CESWD).
Our test results show that enhanced SWD is better than enhanced SRME, and CESWD is better than enhanced SWD. Finally a comparison of these methods is presented by applying them to a real data example. The enhanced methods produce better results than their conventional counterparts.
|Simultaneous determination of anisotropic parameters in PSTM© (presented at SEG, Las Vegas, Nevada, USA, November 4-9, 2012)
Much exploration prospecting is still done on Prestack Time Migrated data. The stability and smooth response of this imaging technique plays an important role in all structural and stratigraphic interpretation work. The importance of a good time migration with AVO friendly flat gathers cannot be overemphasized, even if the final product is a depth migrated image.
In this paper we will present a solution to a long standing problem that has haunted time migration algorithms, especially in the presence of anisotropy: how to determine the correct velocities (interval and rms) and the anisotropy parameter ? simultaneously in a manner that the PSTM gathers are flat.
|Multidimensional interpolation on a very sparse 3D, an example from east Texas© (presented at SEG, Las Vegas, Nevada, USA, November 4-9, 2012)
Multi-dimensional interpolators have become a powerful tool for land processing. In this paper we will review the 5D semblance based technology behind the interpolator introduced elsewhere (Wojslow et al. 2012) and then apply it to an extremely sparse 3D land data set from East Texas. The results will then be analyzed and compared to 2D and 3D un-interpolated versions of processing. The results will show that the interpolation and regularization of this data set produced noteworthy improvement when compared to pre-stack time migration processing and made the interpretation easier.
|2D predictive shallow water demulltiple© (presented at SEG, Las Vegas, Nevada, USA, November 4-9, 2012)
Surface Related Multiple Elimination (SRME) can remove free surface multiples for most marine situations; the exception comes when shallow water multiples are present, primarily due to having a poor water bottom reflection. Tau-P decon is routinely and effectively used on land and transition zones data for (interbed) multiple removal. However, in shallow water environments these techniques are not that effective.
Some model-driven methods for Shallow Water Demultiple (SWD) have been developed in the past with partial success. The success of multiple elimination relies heavily on the ability to make an accurate water bottom model. The current trend in the industry for SWD is to derive a 2D predictive operator with a predictive lag calculated from bathymetry, thus making it a totally data driven method. This approach has showed some success but much is left to be done.
In this paper a data-driven method which is inherently more challenging, but produces better results, will be presented. This method is especially designed to operate in shallow waters. In it there is no need to reconstruct the water bottom reflection; instead a 2D prediction operator is derived directly from the data to compute the multiple predictions.
Tests results show that the SWD methodology can produce better results than SRME. Furthermore we will also show that a cascaded SWD→SRME approach can give an even better result than either of these applied alone. We have successfully applied this technique in many production environments around the world and we will show some examples in this paper.
|Multidimensional Land Noise Elimination Technology: 5D Semblance Based Algorithms in Exploration: Theory and Practice© (presented at EAGE, Copenhagen, Denmark, June 2012)
A generalization of the standard semblance equation is used to develop a 5D noise elimination algorithm. After explaining the methodology we illustrate its power by applying it to a real seismic data set. Additionally, we will compare the results to the 3D version of the same program and show that the inclusion of the extra dimensions greatly benefits the noise cancelation process.
|Shallow water demultiple using a multichannel prediction© (presented at EAGE, Copenhagen, Denmark, June 2012)
Surface Related Multiple Elimination (SRME) can remove free surface multiples for most marine situations; the exception comes with the shallow water multiples, primarily due to having poor water bottom reflection. More effective ways are needed to eliminate these types of multiples in shallow water environments.
Many model-driven methods for Shallow Water Demultiple (SWD) have been developed in the past with partial success. The success of multiple predictions lays heavily on the ability to make an accurate water bottom model. The current trend in the industry for SWD is to derive a 2D predictive operator with a predictive lag calculated from bathymetry, thus making it a totally data driven method. This approach has showed some improvements but much is left to be done.
We derive and present here a data-driven method which is inherently more challenging but as we shall see it produces better results. Tests results show that our SWD methodology works better than SRME. Furthermore we will also show that a cascaded SWD→SRME approach can give an even better result than either of these applied alone.
We have successfully applied this technique in many production environments around the world and we will show some examples in this paper.
|Enhanced shallow water demultiple with water bottom reflection modeling© (presented at EAGE, Copenhagen, Denmark, June 2012)
Shallow Water Demultiple (SWD) is a very challenging problem for marine seismic data processing. In shallow water environments, water bottom reflections are recorded only on a few near offset traces because critical reflection angle is reached quickly. In very shallow water, water bottom reflections may disappear completely. This poses a limitation to any convolution based demultiple methods such as Surface Related Multiple Elimination (SRME) and SWD to predict first order multiple.
In this paper we propose a way to enhance these aforementioned methods by modeling the water bottom reflection and then adding it to the recorded seismic data. The modified data can then be used to predict first order multiple using SRME and/or SWD. We call these methods enhanced SRME and enhanced SWD, respectively. We will also demonstrate that an optimal way to perform the multiple elimination is to cascade the enhanced SWD followed by SRME. We call this methodology Cascaded Enhanced Shallow Water Demultiple (CESWD).
Our test results show that enhanced SWD is better than enhanced SRME, and CESWD is better than enhanced SWD. Finally a comparison of these methods is presented by applying them to a real data example. The enhanced methods produce better than their conventional counterparts.
|High Resolution Imaging and Reservoir Characterization of Complex Thin Tertiary Yegua Sands in Texas© (presented at EAGE, Vienna, Austria, May 23-26, 2011)
A unique resolution enhancement with bandwidth extension technique using the Continuous Wavelet Transform (CWT) and harmonics principle is described. Applying this technique the available bandwidth in the seismic data, the phase and amplitude spectra of harmonics and sub-harmonics can be computed. These harmonic and sub-harmonic frequencies are then convolved onto the recorded seismic data. Only frequencies for reflectivity that is above the ambient noise level in the CWT domain is added to the seismic wavelet. This process which can be applied before and after migration broadens the bandwidth of the signal which increases the seismic resolution.
A holistic workflow of rigorous prestack data conditioning, bandwidth extension, petrophysical evaluation, and simultaneous three-term prestack inversion was applied to resolve and characterize the complex thin Yegua reservoirs in Texas along the coast of Gulf of Mexico. The benefit of high resolution processing and high resolution inversion was demonstrated using real data in this paper for better thin sands detection, reservoir characterization, well planning, and field management in a complicated geological setting.
Carbonate Reservoir Characterization with Rock Property Inversion for Edwards Reef Complex© (presented at EAGE, Vienna, Austria, May 23-26, 2011)
Carbonate reservoirs account for more than 50% of total known reserves in the world. Identifying this important reservoir rock and its porosity from seismic data is an essential task in exploring and exploiting carbonate reservoirs for the oil and gas industry. We demonstrate a data driven approach that utilizes bandwidth extension to increase resolution and aid in mitigating NMO stretch, followed by three-term AVA inversion and petro-elastic evaluation for rock properties conversion. By computing bulk modulus and Young's modulus from the elastic properties P-wave velocity Vp, S-wave velocity Vs and density, porosity and lithology can be predicted. A case study is performed in the Middle Cretaceous aged Edwards reef of South Texas and the successful results confirmed by wells are presented.
|High Resolution Processing and Imaging for Subtle Geological Features© (presented at EAGE, Vienna, Austria, May 23-26, 2011)
We show that by extending bandwidth prior to migration the spatial resolution (lateral and vertical) can be improved, and that velocity analysis can give a more detailed velocity profile which in turn improves image quality. An increase in bandwidth prior to migration reduces both vertical and lateral wavelet widths, and, therefore, increases spatial resolution. Improved spatial resolution allows a more detailed velocity field to be defined both laterally and vertically. This approach can be applied to both time and depth migration flows.
High resolution imaging for subtle geological features in the Llanos basin© (presented at SBGf, Rio de Janeiro, Brazil, August 15-17, 2011)
We demonstrate in a seismic processing project from the Llanos basin in Colombia that increasing bandwidth prior to migration can improve the spatial (lateral and vertical) resolution and the subsequent velocity analysis can produce a more detailed velocity profile which in turn improves image quality. The increase in bandwidth prior to migration reduces both vertical and lateral wavelet widths and, thus, increases spatial resolution. The improved spatial resolution in turn permits a more detailed velocity field to be defined both laterally and vertically. This approach, bandwidth expansion prior to migration, can be applied to both time and depth migration flows.
We apply the high resolution imaging technique to the relatively thin Oligocene to Early Miocene Carbonera sandstones from the Llanos basin. Traps are typically three-way structural closures bounded by faults with relatively small throws. Using the high-resolution imaging, the thin sands, their lateral pinchouts and the fault locations can be more accurately mapped reducing exploration risk.
|Business intelligence for exploration and production of shale gas and its data revolution© (presented at SBGf, Rio de Janeiro, Brazil, August 15-17, 2011)
The economics of shale play development requires large numbers of wells to be drilled and completed quicklly. This demands a sophisticated supply chain, leading many operators to adopt an industrial approach to their exploration and production systems. Crucial to this is a new kind of business intelligence hub: the adaptive, real-time database. But the benefits of such an approach are not limited to shale operators. We argue that the data management philosophy applied to shale plays simply raises the bar for the next generation of exploration and production systems. Furthermore, the adoption of a modern business intelligence systm to the enterprise can deliver real increases to asset values - far in excess of their cost of implementation.
Orthorhombic Migrations for Imaging Fractured Reservoirs© (presented at SBGf, Rio de Janeiro, Brazil, August 15-17, 2011)
The combined effects of horizontal layering and vertical fracturing in the reservoir produce orthorhombic anisotropy. In order to properly image these kinds of reservoirs, we need to abandon the simple assumption of VTI and HTI as independent effects, used in current migration algorithms, and adopt new simultaneous accountings of both effects in the form of an orthorhombic time migration. In this paper we will describe the theoretical underpinning of orthorhombic symmetry, how we use it in migration and then show some results on real data. A discussion about the challenges associated with doing velocity updating will be briefly discussed at the end of the article.
|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.
|Characterization of Thin Turbiditic Sands in the Cantabrian Sea through Bandwidth Extension© (presented at EAGE, Barcelona, Spain, 14-17 June 2010)
3D seismic data acquired in the Ballena permits has been reprocessed by REPSOL during 2009 using the technique known as Bandwidth Extension (Smith et al., 2008). The target of the reprocessing was to broaden the seismic bandwidth and increase the temporal resolution of the 3D data over the Xana accumulation, in order to better image the oil-bearing thin turbiditic sands which are the main reservoir of the area. As a result of the reprocessing, peak frequency of the data increased from 22 Hz to 58 Hz and the vertical resolution improved from 25 m down to 12 m. Successive seismic prestack inversion of the bandwidth extended data led to the interpretation of two separate Santonian turbidite lobes of oil-bearing sands which were drilled by the wells MCC-3 and MCC-4, and a third different Cenomanian turbiditic sand body drilled by the well MCC-2. New structural and thickness maps have been elaborated and offered a better understanding of the geology and reservoir sand distribution.
|Is Your Prospect Sealed - From a Geophysical and Pore Pressure Perspective© (presented at EAGE, Barcelona, Spain, 14-17 June 2010)
For a typical prospect evaluation, the three main technical elements are migration, reservoir and trap. Traditionally geoscientists employ structural interpretation to assess the trap or seal integrity. In this paper we focus on how to use pore pressure to evaluate the seal integrity since without a proper trap mechanism or seal integrity, the hydrocarbons would continue to migrate out of the reservoir and result in no prospect.
|A Quantitative Evaluation of Input Data Variables for Model-based PP Inversion Using Conjugate Gradient Algorithm© (presented at EAGE, Barcelona, Spain, 14-17 June 2010)|
Using any model-based pre-stack inversion process requires three types of input data: wavelet, initial model and seismic gathers. In this paper we analyze the impact of the errors possible, such as wavelet estimation errors, initial model errors and seismic signal to noise ratio (SNR), using the non-linear conjugate gradient method for inversion to P-wave velocity (Vp), S-wave velocity (Vs) and density data. Using this synthetic model response as the recorded seismic data, we compare the inversion results to the Vp, Vs and density from actual well data for three zones of interest. Improper rock properties from the inversion will lead to incorrect conclusions about the viability of a prospect. We arrive at conclusions about the impact of wavelet, initial model and seismic SNR required for acceptable inversion. We also offer suggestions for future research and development to increase the accuracy of the inversion results.
|Is Thin Turbiditic Sand Winning - A Case Study on High Resolution Processing and Interpretation?© (presented at EAGE, Barcelona, Spain, 14-17 June 2010)
For an asset team one of many challenges is to accurately map the reservoirs for rock volume estimation in order to establish a development plan. However, when the reservoirs are thin they become more difficult to map given limitations of conventional seismic bandwidth. In this paper we present a real case study of processing a 2005 3D seismic dataset in REPSOL's Ballena permits, offshore North Spain. We describe a workflow of producing high resolution inversion results through a resolution enhancement technique (Bandwidth Extension), a processing sequence to optimize prestack data quality and a 3-term prestack seismic inversion. The resolution-enhanced seismic data and inversion results were able to increase the vertical resolution from 25 m to 12 m with better ties to the known wells in the area. The results further helped individualize the thin turbiditic sands into two different lobes which were difficult to map using normal bandwidth data and inversion results.
|Orthorhombic HTI + VTI Wide Azimuth Prestack Time Migration© (presented at SEG, Denver, Colorado USA, October 17-22, 2010)
The correct imaging of Fractured Reservoirs involves the extension of Migration algorithms to include azimuthal anisotropic (HTI) corrections. Most resource plays involve fractured shales in environments that also exhibit strong vertical anisotropy (VTI). Evidence will be presented to argue that a simultaneous treatment of these effects is necessary to properly focus and image the prospects. Furthermore, we will present an implementation of PSTM that accounts for both kinds of anisotropy. We will also describe the extension of our surface fitting algorithm to derive velocity and anisotropic parameters necessary for a proper migration.
High Resolution Enhancement and Interpretation for Thin Yegua Sands in Texas© (presented at SEG, Denver, Colorado USA, October 17-22, 2010)
We show a novel method of bandwidth extension using the Continuous Wavelet Transform (CWT) and the principle of harmonics. 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 seismic resolution. This bandwidth extension combined with a systematic prestack data conditioning workflow and prestack inversion was applied to resolve and characterize complex thin Yegua reservoirs in Texas. The benefit of high resolution and inversion was demonstrated within this paper for better thin reservoir detection and reservoir characterization.
|Rock property inversion for carbonate porosity in the Edwards reef complex© (presented at SEG, Denver, Colorado USA, October 17-22, 2010)
With nearly 50% of all known reserves in carbonate reservoirs, identifying potential reservoir rock from seismic data, in particular porosity, is an important endeavor in exploring and exploiting carbonate reservoirs. We show a data driven approach that utilizes bandwidth extension to increase resolution and aid in mitigating NMO stretch, followed by 3-parameter AVA inversion and impedance inversion to rock properties. By computing bulk modulus and Young's modulus from the elastic properties Vp, Vs and density, porosity and lithology can be predicted. A case study is performed in the Middle Cretaceous aged Edwards reef of South Texas and the results are shown.
|Application of POCS interpolation to exploration© (presented at SEG, Denver, Colorado, October 17-22, 2010)
Powerful new algorithms have emerged in the last few years that are taking interpolation of sparse data sets to a new level of sophistication. Projection onto a Convex Set, or POCS, is one of these algorithms. In this paper we will briefly review the technique and demonstrate its usefulness and versatility in many areas of geophysical data processing. From extrapolation to zero offset for 3D SRME to regularization in the offset vector tile (OVT) domain to enhance imaging, we show that this powerful technique has many potential applications.
|Wide-azimuth land processing: Fracture detection using offset vector tile technology (The Leading Edge, November 2010)
Using a modern wide-azimuth land survey, we demonstrate the power of offset vector tile (OVT) processing and subsequent analysis of offset vector gathers (OVG) to identify potential anisotropy and fracture characteristics of certain reservoirs of interest. Migration of the inherently azimuth-limited OVT gathers and the accompanying velocity updating scheme, based on surface fitting in offset and azimuth, yields robust measurements critical to this analysis. Both the kinematic and dynamic aspects of the processing are considered and contrasted. The results of the processing and analysis are then confirmed by comparison to the values predicted from two wells in the area.
|A successful statics methodology for land data (The Leading Edge, February 2009)
The distortion effects of near-surface anomalies on the quality of the final (migrated) images have long been recognized as a source of risk for land exploration. The proper accounting of these effects is absolutely necessary for an accurate subsurface image of the prospect to emerge.
|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.
|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.
|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.
|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.
|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.
|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.
|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.
|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.
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.
of 3D Visualization Using Pore Pressure Data (Upstream Technology,
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.
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.
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
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.
|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.
|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.
between a rock and a hard place (Hart's E&P, January 2006)
Windows-based visualization of high-frequency seismic volumes
optimizes reservoir potential in a channel play.
others missed (Hart's E&P, February 2006)
Utilizing HFI™ and AVO on reprocessed seismic data in mature
fields continues to be successful in identifying bypassed
provides quantitative data (Offshore, March 2006)
Time-lapse seismic technique guides field management.
Frequency Imaging in an Exploitation Production Environment
- The Murzuq Basin, Case History
Interpretation of high-resolution 3-D seismic imaging identifies
subtle stratigraphic and structural changes that help in the
placement of water injection wells and the development of
new drilling opportunities in the Murzuq Basin, onshore Libya
Case Study. Presented at the EAGE, Vienna, Austria, 12-15
| Change connections
in the loop (Hart's E&P, September 2006)
Until recently, processing stages have functioned in a self-contained
manner. Now companies are connecting the dots.
contact monitoring at Troll using high resolution 4D analysis
and neural networks
Presented at EAGE, Madrid, Spain, 13-16 June 2005.
3D Seismic Interpretation Using HFI™ seismic Data, Fault Throw,
and Stress Analysis for Fault Reactivation in the Cogollo
Group, Lower Cretaceous, Urdaneta West Field, Maracaibo Basin
As part of a reservoir modeling project, a detailed structural
interpretation of 1150 km2 of HFI™ seismic volume was carried
out. The number of normal faults substantially increased with
this interpretation. The fault trend is related to the preferential
flow direction of fluids in the reservoirs. Presented at the
2005 SPE Latin American and Caribbean Petroleum Engineering
Conference held in Rio de Janeiro, Brazil, 22 June 2005.
Computing Stature Likely to Grow (The Houston Chronicle, September
Geotrace is listed in top 10 supercomputers in Texas.
4D processing and quantitative analysis on Troll West using
multiple vintages of legacy data (First Break, September 2005)
Reaps Results (American Oil and Gas Reporter, October 2005)
High resolution 3-D volumes of interpretable data with the
proper spatial positioning have long been a goal of the oil
and natural gas industry, and many techniques for achieving
it have been developed through the years. Everything from
newer acquisition techniques to methods for compensating for
the absorption and dispersion effects that lower the frequency
content of the data have been introduced and are now being
used in production environments. This interesting development
is part of a broader "resolution revolution" or
the ongoing trend toward ever-higher data resolution and imaging
|Better Resolution or Coincidence? (AAPG Explorer, October - November 2001)
Many attempts have been made throughout the history of modern seismic to image thin beds (<1/4 of dominant wavelength) by extracting higher frequencies from seismic. In addition to simply imaging zones below normal resolution, two of the more common goals to aid in reservoir development are: 1) to define pinchouts of producing zones, and 2) to resolve internal bed geometries. Techniques to enhance seismic frequencies are critical to achieve optimum thin bed resolution.