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73rd EAGE Conference and Exhibition - Workshops 2011
- Conference date: 23 May 2011 - 27 May 2011
- Location: Vienna, Austria
- ISBN: 978-90-73834-13-2
- Published: 27 May 2011
21 - 40 of 129 results
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Experiences of ADX-Energy in the SouthEast Pannonian Basin, Romania - Stratigraphic Opportunities in a Mature Area
Authors Paul Fink and Szilamér KovácsThe general consensus for the Neogene Pannonian Basin is that it is in a late mature hydrocarbon exploration stage and almost all valid structural traps have been drilled. Any remaining potential of economic interest was to be found in deep pre-Tertiary traps, unconventional traps such as basin centred & shale gas and stratigraphic traps (e.g., Tari et al. (2006) and Clayton et al. (1994)). Whilst the deliberate search for stratigraphic traps with modern exploration tools is well underway and with documented success in the Hungarian and Austrian parts of the basin (Arzmueller et al. (2006)) , this is probably not universally true for the Serbian and Romanian part of the Pannonian basin. (The only published paper of a modern 3D seismic based sequence stratigraphic interpretation on the Romanian side known to the authors is Velescu et. al. (2005)). Given that several stratigraphic discoveries have however been drilled by chance and proven to work also in Romania, there is a case to be made for remaining exploration potential in stratighraphic traps in an area which has seen hardly any 3D seismic acquisition and little high resolution modern 2D seismic. (This of course does not exclude overlooked potential in classic structural traps and unconventional plays). ADX-Energy (ADX) has therefore participated in the 2010 Romanian licensing round and won an exploration block (Parta, 1,221 sqkm area) in the Southeast Pannonian basin of Western Romania (Figure 1).
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Oldest Hydrocarbon-producing Fields in the Vienna Basin (Austria)
More LessOil Exploration in the Vienna Basin started in the 1930ies in Austria. But the first oil discovery was made 1914 near Egbel due to sipping gas spills near the surface (Janoschek, 1942). Geologists concluded that the Sarmatian layers from the neighbour country are continuing to the South. The successful well in Slovakia led to drilling campaigns in the central part of the Vienna Basin in Austria. The first productive well (Gösting I) was drilled in 1931-1932 (Friedl, 1936). During this time lots of oil fields, owned by various companies, were developed in the Vienna Basin. Since 1995, OMV is holding nearly all the licenses of the Austrian part of the Vienna Basin. Only three small licenses remained in the ownership of RAG-Austria and two of them (Gaiselberg and RAG-Field; Figure 1) are still producing.
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New Insights Into The Hydrocarbon System Of The Getic Depression, Romania: Implications For Exploration
The Getic Depression represents the foothills of the Southern Carpathians, north of the plains of Moesia, typically described as the foreland of the Southern Carpathians (Fig. 1). The eastern part of the depression is interpreted as the continuation, albeit on a smaller scale, of the Eastern Carpathians. Conversely, the western part of the depression corresponds to a Paleogene to Early Miocene strike-slip basin (i.e. the Getic Basin) developed on the contact zone between the Carpathians and Moesia and thrusted over Moesia during the Mid Miocene. The Getic Depression is a mature petroleum province with thousands of wells drilled and several fields discovered since the exploration started more than 100 years ago (Fig. 1). The shallow structural plays have been intensively drilled in the past. In turn, only a small number of wells targeted deep objectives typically located at more than 4 km depth. These deep wells had only limited success, but indicated the presence of a working petroleum system.
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Exploration in and Below the Thrust Front of the Eastern Alps
More LessThe foreland basin of the Eastern Alps (Fig. 1) is intensively explored since the mid-50s. RAG´s second exploration well was drilled 1955 in the eastern imbricates based on single fold 2D lines on a proposed anticlinal structure. The anticlinal structure was defined by surface geology, shallow pilot wells and 1 fold 2D seismic lines, but the well missed the structure. Since 1955 more than 1000 wells have been drilled in the Upper Austrian and Bavarian part of the Molasse basin, the vast majority in the undeformed part of the basin. Only a few wells were drilled in the Molasse imbricate zone. Reason of failure in the imbricated Molasse were seismically poor defined structures in the complex deformed Molasse imbricates but also the poorly understood depositional history and the prediction of reservoir rocks. The structural and sedimentological features of the Molasse imbricates were illuminated by the implementation of seismic volume based interpretation of large 3D-seismic surveys, acquired during the last decade.
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The Modern Exploration Methods Application Experiences in Vienna Basin and East Slovakian Basin
Authors Branislav Šály, Ivan Hlavatý and Vladimír JureňaCrucial question is: “Are there any reasons to run exploration in mature highly exploited basins?” There are few reasons: - Lot of analogies from known fields available - Infrastructure available, - Possible alternative use of small reserves or low capacity fields (co generation units) Vienna Basin and East Slovakia Basin present traditional exploration areas in Slovak Republic. The first exploration well in Vienna Basin, and also in the whole Slovakia, was drilled in 1913, in the vicinity of Gbely. In East Slovakian Basin the exploration for hydrocarbons started in the middle of last century. Since that time is the exploration and production ongoing. Main progress of the modern exploration methods started in the last decade of 20th century. It has been accompanied by realizing of 3D seismic measurement, analyzing of seismic attributes, using of modern methods of seismic interpretation and implementing of sequence stratigraphy. Also risk analysis was involved in our prospect evaluation. Identification of the new tectonic structures or even development of a new tectonic pattern (in ESB), new play concept and consequently discovering of new hydrocarbon traps are the main results of application modern exploration methods.
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Wedge Top Exploration In Romanian East Carpathians - Seismic Image Of Triangle Zone
Authors A.L. Stan, Serghie Mihalache and Rodica Mihaela SolgaRomania has an extensive experience in oil and gas exploration. Almost, entire geological units with oil and gas bearing potential are covered by 2D and 3D seismic information and thousands of wells were drilled. Rompetrol owns five exploration licenses (figure 1) on blocks: EP I - 5 Gresu, EP I- Nereju, E III Focsani, E IV -5 Satu Mare and E IV – 3 Zegujani. For Gresu and Nereju blocks Concession Agreements were signed with National Agency for Mineral Resources (NAMR) in 1997 by Anschutz Romania Corporation in 1997, company bought by 73rd EAGE Conference & Exhibition incorporating SPE EUROPEC 2011 Vienna, Austria, 23-26 May 2011 Forest Romania Corporation in 1998. In 2005, both licenses were transferred from Forest Oil Corporation to Rompetrol SA. Rompetrol SA is 100% title holder in Gresu and Nereju Blocks.
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Exploration in the Vienna Basin (Austria) – Tools and Methods
Authors Philipp Strauss, Klaus Pelz and Wolfgang SiedlPetroleum companies have been exploring the Vienna Basin for oil and gas for nearly 100 years. OMV owns two Austrian concession areas since the early 1960ies: the Waschberg Zone (with the Flysch and Molasse) and the Austrian part of the Vienna Basin. The exploration areas are vertically divided into three levels: level 1 with Neogene strata (Miocene sediments), level 2 holding units formed during alpine orogeny (Calcareous Alps and Flysch) and level 3 representing the autochthonous units of the European basement. Level 2 and 3 are summarized as Pre-Neogene. The geological and tectonic setting for each of these three levels is diverse with a different age, style of deformation, and lithology; hence the methodology and strategy of exploration is adapted to each level. For level 1, the Miocene strata, 3D seismic interpretation, seismic attributes and sequence stratigraphy are standard tools for exploration. In contrast, for the Pre- Neogene (level 2 & 3) geological and structural modelling are more important and seismic interpretation is applicable for structural mapping only due to medium or poor quality of seismic data.
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Slope-toe Turbidite Systems Related to Aggradational - Progradational Sequences: Potential Stratigraphic Traps in the Makó Trough, Pannonian Basin, Hungary
Authors Orsolya Sztanó, Péter Szafián, Gábor Bada, Daniel W. Hughes and Roderick J. WallisThough the Makó Trough is best known as the location of major unconventional gas accumulations, the thick Neogene to Quaternary sedimentary successions may contain conventional HC resources as well. Structurally controlled traps are widespread on the neighbouring basement highs and not likely to occur in the basin interior. However, stratigraphic traps, untested so far, were identified in relation to the basin-filling progradational slope system. The style and pace of slope advancing are the key to understand sand delivery to and formation of potential reservoirs in the deep parts of the basin.
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Pre-Tertiary Play types of the NW Pannonian Basin, Hungary
Authors G. Tari, Mike Peffer and Gabor VargaCompared to the rest of the Pannonian Basin system, the Hungarian part of the Danube Basin (Fig. 1) appears to be underexplored. Most of the hydrocarbon exploration efforts concentrated on the Tertiary basin fill and, typically, the well penetrations into the pre-Tertiary “basement” were only on the order of a few tens of meters. Whereas the presence of a pre-Tertiary Alpine thrust-fold belt beneath the Miocene to Recent basin fill has been suggested by several authors based on the interpretation of regional 2D reflection seismic data sets, unfortunately, the supposed overthrusts were never proven by drilling. A deliberate search for complex structural traps within the Alpine nappe system, however, provided several recent discoveries beneath the Tertiary basin fill of the nearby Vienna Basin (Fig. 1).
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Western Getic Depression, Romania: New Architecture and Hydrocarbon Potential
Authors M. Tilita, D. Tambrea, Danubian Energy Consulting, A. Boscaneanu and Rompetrol S.AThe Getic Depression/Basin stands out as an old and prolific area for hydrocarbons in the Central and Eastern Europe. Our case study area refers to its western part, also known in the petroleum “language” as Zegujani area. The basin evolved during Tertiary overlapping the contact of South Carpathian and Moesian Platform, being in fact the South Carpathian orogen foredeep. Deposition started with Upper Cretaceous cycles and was continuous, excepting a few hiatuses, up to Pliocene. Despite the overall compressional tectonic regime, much of the tectonic evolution on the Getic western part was conditioned by the evolution of Timok transtensional system.. Most of the exploration works were focused on the central-eastern part of the Getic Depression, motivated by the discovery of several large oil fields (e.g., Ticleni field), while the western part was somehow neglected, due to the lack of commercial discoveries.
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Exploration of a Palaeogene Syn- to early Post Orogenic Deep-Marine Basin Play, Kamchia Depression (Eastern Onshore Bulgaria)
The Kamchia Depression is the easternmost onshore part of the Balkan Foredeep in Bulgaria (Figure 1). It has a long history of petroleum exploration and production numerous wells drilled, often before seismic. There has been limited gas production to date, but there have been numerous shows of gas and gas condensate from a range of late Mesozoic to Oligocene reservoirs, in some cases with high recorded flow rates. Exploration plays exist in the (i) allochthonous and para-autochthonus Balkan Thrust belt; (ii) autochthonous Mesozoic and early Palaeogene normal fault block highs in the foreland (analogous to the offshore Galata Field, Currie et al., (2010)), and (iii) the syn- to early postorogenic fore-Balkan trough (the Kamchia Basin) The focus of this study are thick (up to 1100m) Palaeogene turbidites deposited prior to, during and after the emplacement of the Balkan thrust sheets. Legacy well data shows numerous thick and porous sandstone units, many of which flowed gas but were not developed or were drilled prior to seismic acquisition and were not drilled in optimal positions. The distribution of reservoir sands has been enigmatic, with rapid changes in facies and thickness presenting a major risk in ongoing exploration. The key exploration challenges in this region have been understanding and predicting (i) the rapid changes in facies, sand presence and reservoir quality and (ii) charge and seal effectiveness for individual sands intervals.
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How Reliable is Statistical Wavelet Estimation?
Authors Jonathan E. Edgar and Mirko van der BaanWavelet phase mismatches frequently occur between final processed seismic data and synthetics created from well logs. During processing, deterministic zero-phase wavelet shaping corrections are often favoured over statistical approaches. The remaining phase mismatches are eliminated through additional phase corrections using well logs as ground truth. Thus a phase match between the data and synthetics is forced. Irrespective of the validity of this phase correction method, well logs are not always available and can predict different phase corrections at nearby locations. Thus, there is a need for a wavelet estimation method that can reliably predict phase from the seismic data, without reliance on well log control. Such a method can be used for phase extrapolation away from wells, serve as a quality control tool, or even act as a standalone wavelet estimation technique. We test three current statistical wavelet estimation methods against the deterministic method of seismic-to-well ties. Specifically, we explore the extent to which the choice of method influences the estimated wavelet phase, with the aim of finding a statistical method which consistently predicts a phase in agreement with that obtained from well logs (Figure 1). We question whether well logs are always the optimum source of wavelet phase information and advocate the use of statistical methods as a complementary tool or reliable alternative.
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Robust Surface-Consistent Deconvolution: Creating Inversion Ready Land Data
More LessWe define the concept of “inversion ready seismic data” to mean that the embedded wavelet in the data is everywhere the same, has a known phase (preferably zero-phase) and is convolved with the reflectivity series of the earth. Effects of factors such as variable noise, multiples, near surface absorption and non-white reflectivity leave deconvolved land data far from the ideal. Surface consistent deconvolution is one important step in land data processing toward preparing the data for inversion and AVO. Over the years, various methods of surface-consistent deconvolution have been used in order to mitigate the effect of noise on the deconvolution operators. I limit the discussion in this paper to spiking deconvolution for operator generation, because the use of predictive or so-called gap deconvolution operators supply little or no possibility for increasing the phase stability of land data.
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Near-surface Variations and Onshore Time-lapse Seismic
More LessDifferent from the offshore time-lapse seismic, convincing successes for onshore environments have been reported mainly for shallow reservoirs with large changes in acoustic impedance. This report describes three onshore 4D seismic trials. It is shown that the near-surface variations hamper the measurement of small reservoir changes. Some additional measures in acquisition may have to be taken, as current processing technology is not yet able to solve for the rapid spatial and temporal changes in the near-surface. These measures include an increase in multiplicity, direct calibration of dynamite shots and acquisition with multiple, adequately sampled, buried receivers, which are required to reconstruct the seasonally changing ghosts. Processing offers scope as well to improve repeatability, such as improved tools to derive detailed near-surface models.
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Anelastic AVO: Open Issues in Quantitative Inversion of Dispersive Reflectivity Data
Authors Kristopher A. Innanen and Chris BirdA practitioner of AVO analysis might plausibly take an interest in anelastic reflection coefficients, which are the subject of this paper, for one of two reasons. One might wish to protect an elastic AVO procedure from errors due to unaccounted for anelastic influences. Or, one might seek to use the variations in such coefficients to infer additional properties of the target. The following discussion is largely insensitive to which of these two attitudes is taken: direct anelastic inverse theory (e.g., Innanen, 2011) leads both to formulas for estimation of fully anelastic parameters (e.g., QP and QS), and, simultaneously, to formulas for estimation of more standard elastic parameters, and the latter are “protected” from that particular source of error. Its focus will be on anelastic AVO/AVF in a theoretical and experimental context, ongoing implementation efforts, and open issues whose resolution will be necessary for anelastic AVF/AVO/AVA inverse theory to be considered in any sense complete.
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Another Look at AVO Killers
Authors B. Milkereit, E. Bongajum and J. HuangFor plane waves, systematic amplitude variations with offset/angle (AVO/AVA) depend on changes in the P-wave, S-wave, density and Poisson's ratio at the plane interface (Young and Braile, 1976). AVO-trends and variations are used in hydrocarbon exploration as fluid/gas indicators (Castagna et al., 1998; Shuey, 1985). The simple 2-layer plane wave approximation may lead to potential pitfalls in the interpretation and inversion of AVO trends (Allen and Peddy, 1993). In land seismics, a number of geological situations introduce a high level of uncertainty for AVO analysis. Here we investigate (1) heterogeneity scale at the reservoir level and (2) significant attenuation (scattering or intrinsic) above the reservoir. Because AVO measurements are obtained from prestack seismic data, noise levels are often high. In addition, source and receiver characteristics, near source effects and geometrical spreading must be included for true amplitude processing (Haase and Stewart, 2010). The effects of heterogeneities on seismic wave propagation can be described in terms of different propagation regimes: quasi-homogeneous for heterogeneities too small to be "seen" by seismic waves, Rayleigh scattering, Mie scattering and small-angle scattering. These scattering regimes cause characteristic amplitude, phase and travel time fluctuations important for the analysis of AVO trends. Wave propagation through heterogeneous media depends on the distribution of physical rock properties (matrix, pore space, fluid/gas composition).
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3D Symmetric Sampling on Land of Sparse Acquisition Geometries
More LessFor successful AVO analysis the quality and reliability of the prestack data has to be ensured by a combination of high-quality acquisition and powerful processing. Therefore, it is appropriate to consider some ingredients of data acquisition that are necessary to achieve reliable reflection amplitudes. Based on two earlier papers (Vermeer, 2010a; 2010b), this paper discusses various ways to improve prestack data quality. I start with a review of the symmetric sampling technique which is in my view the best way of selecting acquisition parameters, followed by a discussion of various aspects of parameter choice that influence final prestack land data quality.
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Vibroseis Wavelet Estimation
Authors Zhouhong Wei, F. Phillips and INOVA Geophysical Equipment LimitedOver the years, Vibroseis method has become the principal data acquisition method in land seismic exploration. For half a century this technology has achieved great success in land seismic exploration. However, this method seems to reach its limits as the search for energy resources continues. Many practical issues arising from field operations have remained theoretically unexplained, for example, inaccurate wavelet estimation. This paper focuses on a new vibrator-ground model to simulate the filtering effects produced by the coupling system of the baseplate and the ground as well as the coupling system between the captured ground mass near the vibrator baseplate and the surrounding earth. This new model is referred as the Vibrator-Coupled Ground Model in this paper. Experimental results show that the weighted-sum ground force, when filtered by the Vibrator-Coupled Ground Model, is proportional to the far-field particle velocity whereas the unfiltered signals are not.
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Geophysics Models
More LessThe title of this workshop, “Effective models leading to business solutions”, gives a good description of the purpose of modelling. The modelling should address the important uncertainties we want to reduce. It should give the result of integration of all the separate knowledge pieces that we have into a response which can’t be predicted from individual information pieces on their own.
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Geological Models
More LessA smart and accurate representation of geology is a key stage for obtaining, from the modelling process, reliable results on which costly investments can be decided. First of all, the predictive value of the model is strongly dependent on the quality of the general architecture of the model. Stacking pattern analysis on cores and logs wells data help to identify the significant sedimentary surfaces –sequence boundaries, maximum flooding surfaces - that bound the stratigraphic sequences. Sequence stratigraphy controls correlations from well-to-well, but also the stratigraphic architecture and sedimentary cycle development that drive the facies distribution in the reservoir. Obviously, stratigraphic units at reservoir scale give the main features for model layering, together with the identification of flow units, vertical permeability barriers, and well completions.
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