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11th Simposio Bolivariano - Exploracion Petrolera en las Cuencas Subandinas
- Conference date: 29 Jul 2012 - 01 Aug 2012
- Location: Cartagena, Colombia
- Published: 29 July 2012
81 - 100 of 184 results
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Volume co-rendering of seismic attributes - a great aid to seismic interpretation
Authors Chopra Satinder and Kurt MarfurtTraditional three-dimensional seismic interpretation was built on 2D work flows and consisted of interpreting a grid of inlines and crosslines from 3D seismic volumes. Such interpretation does not account for the information that exists in the third direction. Besides, conventional seismic amplitude visualization may not display subtle features such as identification of minor faults and thin sands, for which seismic attributes have been designed to enhance one or more components of seismic amplitude such as phase and structural relationships. Significant efforts in the last few years have shown the advantages of interpretation on time and horizon slices, geobody detection as well as multivolume and multiattribute co-rendering. Beginning with the early methods using directional illumination for enhancing subtle fault edges, followed by methods using false-color image techniques (RGB) for merging spectral components, we discuss with the help of examples the need for visualization of seismic attributes using volume co-rendering, keeping in mind the objectives of integration of data and value addition in interpretation. 3D visualization capability when adopted for seismic data interpretation can be a powerful tool that could integrate the different types of data. In addition to seismic data, well log curves (vertical and horizontal), VSP data (2D and 3D), microseismic data, all brought together in a 3D viewer not only provide a convincing visual corroboration of the available data, but also lends higher level of confidence to the interpreter. The future visualization development will be aimed at integrating multi-disciplinary data, which is what is required for meaningful reservoir characterization. The future in visualization is expected to offer unprecedented capabilities which will continue to amaze us.
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Volumetric estimates of seismic reflector rotation and convergence
Authors Chopra Satinder and Kurt MarfurtGeometric attributes such as coherence and curvature are commonly used for mapping structural deformation and depositional environment. Although they are excellent at delineating a subset of seismic stratigraphic features (such as shale-dewatering polygons, injectites, collapse features, mass transport complexes, and overbank deposits) they have only limited value in imaging classic seismic stratigraphy features such as onlap, progradation and erosional truncation. We examine how the newer volumetric attributes can facilitate and quantify the use of seismic stratigraphic analysis workflows to large 3D seismic volumes. Due to the distinct change in reflector dip and/or terminations, erosional unconformities and in particular angular unconformities are relatively easy to recognize on vertical seismic sections. Although there will often be a low-coherence anomaly where reflectors of conflicting dip intersect, these anomalies take considerable skill to interpret. Application of attributes based on the description of seismic reflection patterns can be used to map angular unconformities amongst other features. The convergence/divergence of reflections can be defined by computing the vertical derivative of apparent dip at a userdefined azimuth, and have been extended to 3D reflector convergence azimuth and magnitude estimates. Compressive deformation and wrench faulting cause the fault blocks to rotate. The extent of rotation depends on the size, the comprising lithology and the stress levels. Fault block rotation can also control depositional processes by providing increased accommodation space in subsiding areas and erosional processes in uplifted areas. In view of this importance of the rotation of the fault blocks, we present a seismic attribute that measures the reflector rotation at every sample in the seismic data volume. Application of the reflector convergence and rotation about the normal attributes on two different 3D seismic volumes from Alberta, Canada yields convincing results.
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Euler curvature for observing fracture lineaments
Authors Chopra Satinder and Kurt MarfurtOver the last several years, seismic curvature attributes have been shown to be very useful in the interpretation of flexures and folds which can often be associated with conjugate faults and fractures. Although many curvature measures that have been introduced, we find the most-positive and most-negative principal curvatures k1 and k2 to be the most useful. All other curvature attributes can be derived from the two principal curvatures. For example, some practitioners have found that the components of apparent curvature projected parallel to the dip azimuth and strike of a dipping plane to be useful in given tectonic and stress settings. In this study we describe the theory and application of Euler curvature, which is a generalization of the dip and strike components of curvature in any user-defined direction. Since reflector dip magnitude and azimuth can vary considerably across a seismic survey, it is more useful to equally sample azimuths of Euler curvature on the horizontal x-y plane, project these lines onto the local dipping plane of the reflector, and compute Euler curvature along a given strike direction. The Euler curvature attribute has the advantage that it can be computed from the conventional final migrated stacked volume to obtain the attributes in different azimuthal directions. In this manner, azimuthally-dependent lineament intensity volumes can be correlated to natural and induced fractures seen in image logs to better quantify the presence of natural fracture sweet spots perpendicular to today’s minimum horizontal stress field. We describe the application of Euler curvature to two different 3D seismic volumes from northeast British Columbia, Canada and show that this attribute is useful for the interpretation of lineament features in desired azimuthal directions.
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Non-hyperbolic MultiFocusing improves depth imaging
Authors Alex Berkovitch, Kostya Deev, Marianne Rauch-Davies and Evgeny LandaMultiFocusing technology can dramatically improve the quality of seismic imaging especially in cases of low fold data, poor signal- to- noise ratio and sparse 3D acquisition. At the same time, local parameters of the observed wavefield in prestack seismic records are of great interest for many seismic applications such as signal enhancement, velocity model building, etc. We propose to employ the MultiFocusing idea to achieve this goal. A local common offset MultiFocusing approximation for travel time stacking surface description is used. It allows accurately approximate travel times of reflection events in the vicinity of arbitrary location and arbitrary offset. We present the implementation of two applications: a signal enhancement scheme and velocity model construction by prestack stereotomography. We will also demonstrate efficiency of the proposed applications.
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Modelo tectónico regional sector sur de la cuenca caguán, basado en datos aergeofísicos y morfoestructurales
Authors Isabel Restrepo-Correa and Eduard LópezEl sector Sur de la Cuenca de Caguán se caracteriza por su inaccesibilidad, poco conocimiento geológico y ausencia de datos sísmicos. Basados en la escasa información existente, la región ha sido considerada como una extensión del escudo Brasilero, afectado por una tectónica preMesozoica, con sistemas de horst y grabens con rumbo general NNW. Sin embargo, nuevos datos aerogeofísicos adquiridos por ECOPETROL (5000 km/lineales de aerogravimetría-magnetometría), sumado al análisis de dinámica fluvial basado en imágenes de satélite, permiten postular la existencia de estructuras transversales con rumbo NWW, estructuras circulares y domos. Por otro lado, el modelamiento de métodos potenciales, permitió estimar que el área es un depocentro con espesor del orden de 4 a 6 km, que se extiende en forma elongada hacia el Sur a las provincias petrolíferas de ITT (Itspingo, Tambococha y Tiputini) en Ecuador. A partir del análisis regional, se plantea que la estructuración trasversal observada está genéticamente relacionada a la expulsión del bloque Norandino durante el Neogeno y que probablemente ha permitido la formación de estructuras prospectivas terciarias de hidrocarburos en el área. Está aún por definir la edad de las rocas más antiguas que rellenaron los depocentros y sus propiedades como almacenador y sello.
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Geophysical expression of Late Oligocene-Early Miocene Reservoirs in the Guarrojo area, Llanos Basin of Colombia: from reconnaissance to simultaneous 3D seismic inversion
Authors M. De Freitas, I.C. Flores and J.A. MoraThe Guarrojo block, in the Llanos Basin of Colombia, is a case history of successful exploration where geophysical tools were progressively used from regional, reconnaissance work through to prospect definition, field development and further exploration. Prospective areas were identified with coarse airborne gravity-magnetics and 2D seismic (2005-2006). The first well (Ocelote-1, 2007) resulted in a significant oil discovery in sandstones of the Oligocene Carbonera (C7) Formation. The Ocelote field is currently producing 20,000 bopd, with significant untested potential. Two 3D seismic surveys covering 378 km2 were acquired (2007, 2009) and merged. Seismic interpretation and attribute analyses of pstm and psdm volumes were used for field appraisal and development. In addition, amplitude anomalies and coherence patterns suggested narrow, low sinuosity channels as upside potential in the Carbonera C5 member. The first C5 channel drilled in 2008 resulted in a significant oil discovery. Simultaneous 3D seismic inversion (P-S impedance) allowed for improved characterization of the C7 reservoir, but no fluid discrimination. Nevertheless, the inversion yielded improved estimation of both rock and fluid types of the overlying C5, C3 and C1 members. Sand-prone C5 channels were mapped with enhanced detail and P-S impedance cross-plots potentially discriminate water vs. oil bearing zones. Inversion prediction of oil pools failed in the first new well. Further to a new 3D acquisition and merge (2010), a feasibility analysis including more wells still suggests the power to discriminate fluids. Upon completion of a new run of the simultaneous inversion, additional C5, C7 prospects will be ranked and tested.
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Characterization of the Ciénaga de Oro Formation in the Saman Block, Lower Magdalena Basin, Colombia, using 3D Seismic Inversion and Facies Analysis
Authors M. De Freitas, V.R. Vélez, A. Mesa and J.A. Mora3D seismic-based lithologic characterization of the Oligo-Miocene Cienaga de Oro Formation (COF) was performed in a ~500 sqkm area (Saman) of the Lower Madgalena Basin, Colombia. Facies variations and discontinuities of the COF make the reservoir distribution and quality the critical exploration risk in the basin. The study integrates seismic attributes, facies analysis and inversion (P-impedance), calibrated to 7 wells. The COF overlies an igneous-metamorphic basement, which forms a high amplitude seismic reflector. Both the top and the internal character of the COF present variations across the area. These reflect lithologic changes that can be recognized to some extent with amplitude and other seismic attributes from the pstm volume. However, a significant improvement in the characterization of the COF was obtained with 3D acoustic inversion and seismic facies analysis. The P-impedance volume allowed for an improved discrimination of different depositional events, interpreted as transgressive deposits advancing SE-wards. The basal section, with a very high P-impedance response, is restricted to the northern area and correlates with immature, coarse-grained deposits with poor reservoir properties. The upper section shows a discontinuous distribution of sandstones (exploration target) and shales, with the sand-prone facies correlating to moderate-high P-impedance and the shales to lowest values. Seismic facies analysis, where the variations of the wave form between top and base of the COF were subdivided into eight discrete responses, was performed both in unsupervised mode and constrained by wells. This helped further discriminating prospective (sand-prone) and non-prospective zones (shales or tight sands / conglomerates).
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Descubrimiento del Campo Perla: Un Nuevo Campo Gigante en El Mar Caribe
El campo Perla se encuentra localizado en el Golfo de Venezuela, al occidente de la Península de Paraguaná a una profundidad de 60 m de agua. El yacimiento se sitúa en un área de interacción entre las Placas Caribe y Suramericana, las cuales generan un escenario geológico único y complejo. Los análisis preliminares de sísmica 2D mostraron un alto importante de ~100 km² que motivó al consorcio Repsol-eni a ofertar por el área Cardón IV, durante la Ronda Licitatoria de Gas “Rafael Urdaneta”. Tras la adjudicación del Bloque, se adquirieron más de 700 km² de sísmica 3D que reconfirmaron dos posibles zonas de interés, se caracterizó la primera como Carbonato Superior y la segunda como Carbonato Inferior. El Carbonato Superior cambiaba lateralmente a una unidad más siliciclástica y el Carbonato Inferior se identificó como una construcción carbonática (buildup), sin reflectores internos y con un “dim-spot” claro en el tope de la estructura, con más espesor y potencial. Los cálculos originales estimaron entre 2-6 TCF con un riesgo asociado principalmente al reservorio. El primer pozo exploratorio se perforó a mediados de 2009 (Perla-1X) y probó el Carbonato Inferior de edad Mioceno Inferior como gasífero con un espesor mayor de 240 m. Los estudios detallados identificaron un banco de algas rojas con macroforaminíferos asociados, desarollado en una rampa distalmente acentuada. Posteriormente, se identificó que la estructuración original del basamento definió los ambientes deposicionales. Los siguientes 4 pozos perforados confirmaron el descubrimiento como el mayor campo de gas de Latinoamérica.
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Structural Linking of the Recetor and Piedemonte Areas, and Implications for Hydrocarbon Accumulations, Eastern Cordillera, Colombia
Authors David Richards and Claudia CeballosThe frontal zone of the Eastern Cordillera fold and thrust belt hosts the large fields of Cusiana and Cupiagua that have a long history of production, and as well, there is newer production from thrust sheets to the northeast, in the Recetor, Piedemonte and Niscota blocks (1, 2, 3). The area is structurally complicated and good seismic imaging has proven difficult to obtain in the areas northeast of the Cupiagua-main Recetor structural complex. Effective exploration and development rely on a detailed structural modeling workflow of 2D and 3D balancing, based heavily on well data, in order to achieve a structurally valid 3D seismic interpretation. Drilling based on the resulting 3D structural model has proven successful. The focus of this paper is the structural transition from the main Recetor area to the Piedemonte area. The structural style and trend of the productive and prospective thrust sheets change from the Recetor area to the Piedemonte area. In the main Recetor area, there is one primary producing thrust sheet with limited stacking of the Mirador and other reservoir units. In contrast, from northern Recetor through the Piedemonte area and continuing into the Niscota area there are stacked sheets of the producing reservoirs, with the sheets increasing in number to the northeast, corresponding to increased shortening in the northeastern part of the area in discussion. The overlying Nunchia syncline reflects the change in style and aids in interpretation of the deeper structure. The change in trend and slip direction relates to an area with slight alongstrike shortening, and this component of shortening contributes to development of culminations along strike. The structural modeling has resulted in identification of several opportunities in the area, as well as providing a guide to well planning and reserve estimations.
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National Geoscience Laboratory Network – RNLG
More LessIn many industrialized and developed countries, universities play a key leadership role in academic, research and innovation processes. The Colombia Hydrocarbon Agency (ANH) and the Colombia science foundation (COLCIENCIAS) created an initiative to develop a national Geoscience Laboratory network (RNLG). The RNLG is a technical system that integrates several laboratories belonging to twelve public and private institutions in the field of Geosciences, including universities (EAFIT, UCALDAS, UIS, UNAL, UNIANDES, and UPTC), private institutions (ICP) and public institutions (Colombian Geologic Survey and the Geographic Agustin Codazzi Institute). The integration of these entities allows the RNLG to develop technologies and applications in high priority earth science areas including regional geological analysis, thermocronological, paleomagnetic, bioestratigraphic, and geochemical studies, and remote sensing techniques. The RNLG´s mission is focused on establishing and consolidating high quality laboratories for teaching, research and extension, which in turn generates strategic alliances among its members, government and industry, for the understanding and evaluation of conventional and unconventional hydrocarbon resources, in order to reduce uncertainty in decision-making in the development of the hydrocarbon sector. This will be reflected in encouraging private investment in the exploration and exploitation of hydrocarbons in the country.
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Integrating coherence and seismic inversion for imaging thin bed channel deposits
Authors Carlos Molinares, Richard Brito, Oswaldo davogustto and Kurt MarfurtThis paper describes the advantages of combining energyweighted coherent amplitude gradients, coherence and seismic inversion cubes, for imaging thin bed deposits. These features are related to distributary channel deltaic deposits associated with a transgressive Lower Miocene sequence, located in northwestern Colombia (South America). Because the rapid lateral variations and thickness below tuning resolution, these transgressive channel reservoirs are complicated to develop efficiently and it is difficult to characterize or successfully map them using conventional seismic attributes (e.g. RMS amplitude). Our coherence and energy-weighted coherent amplitude gradients volumes provides high resolution images of lateral variations within the seismic volume, illuminating channels and faults but provide little insight as to which seismic facies may be present. In contrast, our seismic inversion volumes is directly sensitive to lithology and porosity; when coupled with well control it can be used for lithologic and stratigraphic interpretations. These volumes present an unbiased image volume that allow interpreters and reservoir engineers to: 1) display stratigraphic geobodies, 2) compare producing intervals, and 3) predict reservoir continuity for an integrated reservoir characterization.
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Geometric Seismic Attributes for Imaging High Angle Faults and Thin Beds in the Magangue High, Northwestern Colombia
Authors Carlos Molinares, Kurt Marfurt and Victor RamirezNew natural gas discoveries in the Magangue High (Northwestern Colombia) brings new exploration opportunities but also new challenging conditions in an underexplored area. The principal reservoir is related to the Lower Miocene transgressive sandstones (Cienaga de Oro Formation), characterized by a high-energy well-connected marginal marine channel system that ended isolated thin tidal channels. The secondary reservoir is related to early Late Miocene Basal Porquero Formation turbidite sandstones. These two intervals are limited by normal faults, which both generate trap and compartmentalize the reservoir. The first objective of this work was to better map high-angle faults. Seismic attributes such as eigenstructure coherence are sensitive only to waveform changes while others such as Sobel filters and variance are sensitive to both waveform and amplitude changes. In contrast, attributes such as the most-positive and most-negative principal curvatures are sensitive to more diffuse fault zones that appear as flexures. The second objective was to apply geometric seismic attributes sensitive to amplitude changes to image channel features with thickness possibly below tuning resolution. Applying this workflow are able to image thin tidal channels and sand flats that give rise to amplitude changes. We interpret the amplitude contrast between channel infill and surrounding matrix as representing more sandy intervals. We interpret other channels as filled with clay plugs, with reservoir characterization consequences. Co-rendering coherence attributes combined with the principal curvatures were effective in mapping normal faults in the Magangue Arc, key to reservoir characterization and well planning phases.
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Advances in acquiring real-time data using wireless technology
Authors Doug Crice, Roy Kligfield and William ScottLand seismic acquisition has traditionally relied on the use of cables to power the acquisition instruments and to transport the seismic data to a central recorder. However, the logistical issues relating to the use of cables to connect acquisition instruments is a serious handicap. The problems of deploying and maintaining cabled networks, relocating cables in order to move the spread, and repairing cables have acted as constraints on the growth in size and scope of land seismic acquisition projects worldwide. In the recent past, two approaches are being adapted in order to overcome these barriers. In athe first approach, instruments are being deployed as autonomous “blind” nodes whose data has to be collected and transcribed in order to make it ready for processing. In a new approach, instruments are being deployed with the capability to wirelessly transport the seismic data to a central location in real time. Whereas the nodal approach has been successful at eliminating the use of cables, it introduces the need to visit the instruments physically to collect (harvest) the data from the instruments and to prepare the downloaded data (transcription) for input into industry standard formats. The nodal approach precludes any chance of viewing the seismic data immediately. This presentation reviews the initial results of field deployments using a system with realtime wireless data collection, usable in both remote and urban environments. A review of some of the system capabilities and limitations in terms of network throughputs, radio interference issues in urban environments, and the use of different sources will be given. Based on its initial deployments, the solution is entirely capable of being scaled up to support the large channel counts demanded in land seismic operations.
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Effects of Paleogene Subduction on Basin Segmentation and Oil Migration in NW South America
Authors German Bayona, Agustin Cardona, Carlos Jaramillo, Camilo Montes and Andres MoraIn the Northern Andes, inversion of Mesozoic extensional structures controlled location of synorogenic successions, dispersal of detritus and migration pathways since Paleocene time. Detailed tectonostratigraphic analysis conducted in several basins of NW South America indicate that reactivation of former normal faults broke the single Late Cretaceous basin into different depocenters. In the Paleocene to early Eocene, reverse reactivation broke the syn-orogenic basin into two depocenters. The western depocenter (Magdalena and Rancheria basins) was bounded to the west by eastward-tilted crustal blocks and to the east by reactivated structures; crustal tilting and Paleocene marginal and intraplate magmatism were associated to subduction of the buoyant Caribbean plate. Reactivation of older structures migrated eastward and disrupted the eastern depocenter (presently along the axial zone of the Eastern Cordillera, Llanos foothills, Llanos, Catatumbo and western Maracaibo basin). Basin configuration and patterns of deformation changed drastically in middle Eocene time, as subduction of the buoyant Caribbean plate stopped. Strike-slip deformation and localized burial process that favored for oil maduration along western depocenters (southern and middle Magdalena Valley) depict marginal deformation associated to northward migration of the Caribbean plate,. In contrast, quiescence in eastern depocenters favored deposition of reservoir units. As subduction process renewed in Oligocene time, deformation spreadout. The uplift of the bivergent Eastern Cordillera broke definitively the connection of eastern and western depocenters, and began the segmentation of the Llanos basin from the axial zone of the Eastern Cordillera.
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High Dimensional Interpolation and Regularization in Exploration
Authors Jaim Stein and Robert WojslawRegularization and Interpolation in higher dimensions has become an important tool in the processing arsenal of any geophysicist. The reasons for interpolation and regularization of data are many. Some noise elimination techniques work better on regular data sets and some even demand it. Also imaging algorithms, whether it is Prestack Time or Prestack Depth migrations produce better results if the data has been regularized a priori, than during the migration, putting less demand on the migration weights, which are, in general still poorly understood.
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3D SEISMIC ANALYSIS OF SEDIMENTARY DYNAMICS CONSIDERING THE GELASIAN-CALABRIAM CLIMATE TRANSITION FROM LATE PLIOCENE TO PRESENT, AN EXAMPLE OF THE EBRO CONTINENTAL MARGIN
Authors Adriana Grosso and Angelo CamerlenghiAnalysis of industry 3D seismic reflection data on the Ebro continental margin was analized to better understand the evolution of the sedimentary dynamics of the Ebro margin shelf from late Pliocene to present, considering the Gelasian-Calabrian boundary transition from a climate dominated by 41 ka Earth precession cycles to 100 ka obliquity of the Earth’s orbit dominated cycles.
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Dual coil – long offset full azimuth towed streamer acquisition
Authors Tim Bunting, Tim Brice and Nick MoldoveanuOver the last twelve years significant advances have been made to mitigate for the limited azimuth range of towed streamer geometries and subsequently improve imaging in areas of high geological complexity, such as the Gulf of Mexico pre-salt provinces. These advances include acquiring the survey multiple times in different azimuths (MAZ) and acquiring the survey using multiple vessels (WAZ). More recently Coil Shooting has been deployed which utilizes a single towed streamer vessel following a circular pre-plot. However, even with these sophisticated surface geometries, recent experience has shown that the most complex of Gulf of Mexico geologies are still non-optimally imaged. Through a series of modeling efforts, using ray tracing and two-way wave equation methods, the WesternGeco technical team in Houston determined that to solve these most complex imaging problems a ultra-long offset full azimuth measurement was required. The same technical team used these new geometry requirements to develop a new acquisition technique of which Dual Coil is the result. The Dual Coil technique uses four vessels (two recording vessels and two source vessels), sailing in 12.5-km-diameter slightly offset circles. The source vessels sail at the tail of the respective recording spreads and the two recording vessels maintain 180 degrees separation. Ultra-long offsets are achieved by sources shooting across the coil (Moldoveanu and Kapoor 2009; Brice 2011). These circular “lines” are repeated in both directions to build up fold, offset distribution and azimuth distribution. At the time of writing, three dual coil surveys have been acquired in the Gulf of Mexico covering over 550 OCS blocks (13,000km 2). Each with different acquisition and imaging challenges. The final images will take over a year to complete using an intensive data processing flow including variable water velocity correction, 3D Surface Related Multiple Attenuation (SRME) and tilted transverse isotropy model building and imaging. However fast track images were generated on-board and delivered less than a week after completion of acquisition operations. Even using this preliminary model and Isotropic assumptions there is a clear improvement in imaging, when compared to the underlying WAZ image. As well as a general improvement in illumination and signal to noise, the sand beds terminating against the salt body are much easier to interpret. While the Dual Coil technique has been developed to solve specific imaging problems in the Gulf of Mexico associated with large complex salt bodies, there is no reason to think that it would not be appropriate for other difficult-to-image areas around the world such as where thick layers of basalt are present or where carbonate layers distort the ray-paths.
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Point source and point receiver acquisition – potential benefits for columbia
By Tim BuntingWhile land point source and point receiver acquisition is gaining acceptance in certain regional and geological settings its uptake in Latin America has been limited. Historically the industry has tried to solve the problems of surface noise on land seismic surveys by increasing source and receiver effort by using large arrays and by sending lots of signal energy into the ground. Point source and receiver techniques attempt to resolve the problems associated with the complex noise field on land surveys in a more scientific way, by measuring the linear noise modes as faithfully as possible i.e. un-aliased or not disturbed by the use of geophone arrays. In 2007 WesternGeco acquired a point receiver 2D survey at the base of the Al-Hajar mountain range close to Dubai in the UAE at the edge of the Oman thrust belt. The geology is very complex with steeply dipping structure. The survey was acquired on top of a 2003 3D survey out the two acquisitions used radically different approaches, some of which are detailed in table 1. In addition to the use of point receivers and compact source groups, the bandwidth of the sweep was extended at the low end. The final 2007 PSDM images showed significant uplift above the 2003 PSTM processing. The signal to noise is much better, to the point where it is possible to interpret the structural geometry with some level of confidence. It is difficult to draw absolute conclusions when comparing the 2003 time image with the 2007 depth image because of the use of a depth imaging solution. However, the uplift in the pre-imaging measurement will not only benefit the imaging solution but all additional processes, most specifically the velocity modeling which is critical to the depth imaging effort. The combination of all these incremental uplifts can result in significant overall improvement in imaging quality.
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Advances in marine seismic acquisition
Authors Thomas Elboth, Hakon Aune, Eric de Graaff, Margherita Maraschini and Steve ColeLong offset wide azimuth seismic, simultaneous sources (blended acquisition) and ocean bottom nodes are technologies that have been developed in order to fulfill the goals of faster, cheaper and better seismic. In this paper we will present results from recent field tests where we have combined several of these technologies. New and improved hardware makes it possible to control the positions of both sources and streamers with very high (decimeter) accuracy. With recent engineering and processing algorithm advances, it is also possible to acquire blended data (i.e., firing sources at multiple shot locations within a single seismic record), and deblend the data efficiently. By combining source and streamer steering with blended acquisition, we can choose to double the cross-line sampling of 3D and 4D surveys, or acquire extra azimuths (WAZ) without the need to reduce in-line sampling, all in the same time it would take to acquire a conventional survey. By combining these techniques with advanced tools like Fresnel zone binning, we can also significantly reduce the need for infill shooting. In short, we get data faster, cheaper and better. The use of simultaneous sources also offers exciting opportunities when combined with ocean bottom nodes. The extra source(s) efficiently contribute to a higher trace count or reduced acquisition time. De-blending, i.e. the technology of separating data coming from several sources is a key software component in all of these approaches.
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Expanding the role of cable-less equipment in seismic operations
By J. CrissCable-less technology for seismic acquisition has evolved and grown over the last few years. As of Jan 2012, it is estimated that there are over 170,000 cable-less seismic acquisition nodes at work worldwide on over 40 systems. Cable-less seismic equipment poses new challenges in operations, not because it is more difficult to use but because the systems require crews to learn new skill sets and view equipment optimization in a new light. Experience is growing with cable-less systems in the fields of improving operation efficiency, designing more flexible surveys, and meeting tighter project management deadlines. The role of cable-less seismic acquisition equipment is expanding with increased confidence gained by successes in production work, leading toward a brighter future for cable-less seismic hardware systems. This paper will investigate the concerns surrounding system design, the benefits and trade-offs, and the critical factors that made cable-less systems the best solution for some recent successful projects.
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