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EAGE Workshop on Marine Seismic - Focus on Middle East and North Africa
- Conference date: 22 Feb 2009 - 25 Feb 2009
- Location: Limassol, Cyprus
- ISBN: 978-94-6282-068-5
- Published: 22 February 2009
21 - 32 of 32 results
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Challenges of Marine Seismic Project in Block 15, Sudan Red Sea
More LessDuring 2007 marine seismic survey, RSPOC’s contracted 2D seismic vessel equipped with 6-km length streamer cable faced several technical and operational challenges. It is quite a challenging task to process Pre-Stack Time Migration (PSTM) seismic data due to complicated seismic wave ray paths and velocity trends from two different exploration objectives. Additionally, seismic interpretation using 2D seismic dataset requires exceptional interpretation skill with sound-geological model to ensure the result represent an acceptable geological model of Red Sea rift tectonics. The latest Pre-Stack Depth Migration (PSDM) processing sequence has provided better definition of complicated Pre-Miocene Salt Formation fault pattern. With better PSDM seismic velocity dataset, bore hole formation pore pressure trend at the proposed prospect drilling locations could be estimated and predicted in effort to assist the planning of offshore high-pressure and high-temperature (HPHT) wildcat drilling campaign.
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Marine Seismic Data Acquired over the Libyan Offshore Area – A Case History
Authors J.A. Martin, S. Bowman and S. WaddinghamDuring 2004 and 2005, over 38,000km of 2D non-exclusive data were acquired in the waters offshore Libya in cooperation with NOC and NAGECO. This consistent dataset provides regional correlation from the existing developed western fields into the largely un-explored offshore Gulf of Sirt and Cyrenaica regions. It provides a unique resource for reviewing the potential of some of the world’s most prospective acreage and complements NOC in their efforts to boost Exploration in Libyan waters.
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2D Marine Seismic Acquisition for Sub-salt Objectives in the Red Sea
By J.A. MusserSAUDI ARAMCO recently acquired a very large regional 2D reconnaissance marine seismic program in the Red Sea. The objectives of the project were to identify and map potential leads both above and below salt bodies in the Red Sea basin. Streamer length and depth were tested for their impact on low frequency data recovery and imaging of deep objectives. Prestack depth migration results show improvement in deep imaging as the maximum offset is increased from 7200 meters to 10,330 meters. The greatest improvement in depth image quality occurs when offsets of up to 9200 meters are included. New solid streamer technology proved valuable for acquiring the long offsets required by this project while maintaining continuous operations.
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Velocity Model Building and Depth Imaging Challenges – Red Sea 2D Marine Case Study
More LessSaudi Aramco acquired an extensive 2D marine seismic program in the Saudi Arabian portion of the Red Sea during 2007 and 2008. Acquisition utilized a 10 km long solid streamer cable with 816 active hydrophone channels spaced 12.5 meters apart and towed at a 10 meter depth. Shots were taken every 25 meters using an airgun array comprising 25 guns and a total array volume of 4060 cubic inches at a tow depth of 7 meters. This survey was part of an initial exploration phase, and is being used to find leads for 3D acquisition. The geology in the region can change rapidly from younger sediments to complex non-homogeneous salt bodies, anhydrites, limestones, and igneous rocks. We present the challenges encountered in processing a large (20,000+ km) 2D dataset through prestack depth migration (PreSDM), and techniques used to generate the depth images within the project timeline.
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Acquisition and Integrated Interpretation of Controlled Source Electromagnetic (CSEM) Survey Data with Other Geophysical Data Types
By A. GreerControlled source electromagnetic sounding (CSEM) is now becoming a mainstream exploration tool in a wide range of geological environments; and to date the technique has been primarily used on a standalone basis. It is recognised that by accurately integrating CSEM data with other geophysical data types, such as rock physics and seismic, that significant improvements in subsurface understanding can be gained throughout the E&P process.
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Marine Transient EM Surveys
Authors A.M. Ziolkowski and D. WrightWe describe transient electromagnetic (EM) surveys in water depths of about 100 m, where conventional Controlled Source EM (CSEM) has great problems with the air wave. Our proprietary method recovers the complete Earth impulse response, optimising signal strength with offset-dependent coded signals. Air wave removal is straightforward and our new method for removing magnetotelluric (MT) noise increases the low-frequency signal-to-noise ratio by about 20 dB. We demonstrate the techniques on real data from the North Sea.
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Porosity Prediction in Carbonates – Learnings from the North Sea Chalk Applied to Platform Carbonates
Authors A. Uldall and R. Pedersen-TatalovicPorosity can be predicted from seismic data when seismic impedance is correlated with porosity. One of the problems is that the correlation between impedance and porosity can be to a large degree determined by the low-frequency component of impedance, which is not present in seismic data. We explain how to overcome this problem and show the method which we developed while working on North Sea chalk. In addition to broad-band impedance data, the impedance - porosity transforms should be derived separately for different facies, in order to apply the same workflow to platform carbonates.
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AVO Application in a Carbonate Offshore Oil Field, U.A.E.
Authors H. Ikawa, G. Mercado and A. SmithWe will present fluid substitution well log modeling results based on Gassmann's equation and application of conventional AVO and other techniques such as Elastic Impedance and Simultaneous Inversion followed by lambda-rho mu-rho (LMR) techniques in a pilot area of interest. The results of the pilot study were validated with the known well fluid status in the pilot area. Mapping of the different water-oil-gas fluid response using the LMR technique shows a reasonably good agreement with currently known well saturations. It is, however, difficult to discriminate reservoir sub-layer water-cut percentages due to data resolution limitations. Generally, the results of the analysis indicate potential to identify hydrocarbon to water fluid contents, with the above constraints.
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3D-2C OBC Multi-azimuth Seismic Data Processing and Its Applications for a Carbonate Field Offshore Abu Dhabi, UAE
Authors T. Ishiyama, D. Painter, K. Belaid, H. Ikawa, T. Matarid, A. Al-Hendi, A. Mouaki Benani Chebihat and T. SalehA 3D-2C OBC multi-azimuth seismic data processing was conducted in a test area in a carbonate field offshore Abu Dhabi, United Arab Emirates with the main objectives: to demonstrate improvement of imaging; and to detect any HTI response. Three processing flows were designed to generate (i) conventional, (ii) full-azimuth and (iii) multi-azimuth cubes. The output cubes were evaluated qualitatively and quantitatively: (1) overall imaging analysis; (2) fault imaging analysis; and (3) HTI analysis. The results demonstrated improvement of imaging compared to traditional processing and detection of a certain HTI response. These encouraging results will be the incentive to apply multi-azimuth seismic data processing in carbonate fields offshore Abu Dhabi, United Arab Emirates.
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Detailed Velocity Model of the Nile Delta Using Multi-azimuth (MAZ), Multi-Parameter Reflection Tomography
Authors D. Baptiste and T.A. ManningIn the Nile Delta, a complex and dipping water bottom, shallow gas filled channel systems and the evaporitic Messinian interval have prevented the creation of an accurate velocity model in depth using conventional 3D data. By designing a workflow that combines the Multi-Azimuth data in a multi-parameter reflection tomography approach, we have built a detailed velocity model that shows variations that correspond very well to the geology interpreted from the seismic, and which yields improved images at depth.
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Interval Velocity Analysis in Complex Areas – What About the Azimuth?
More LessThree dimensional interval velocity analysis must deal with the problem of lateral velocity variations along different azimuths. Traditionally, when this azimuth dependency is treated, the analysis refers to the acquisition azimuth. The main idea presented in this study is that in complex geological regions, the acquisition azimuth may not be the optimal domain for analyzing velocity errors. We suggest here to define the azimuth in the image domain. Together with the scattering angle and dip, all parameterized in the depth image domain, accurate CIG analysis method can be designed.
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