- Home
- Conferences
- Conference Proceedings
- Conferences
68th EAGE Conference and Exhibition incorporating SPE EUROPEC 2006
- Conference date: 12 Jun 2006 - 15 Jun 2006
- Location: Vienna, Austria
- ISBN: 978-90-73781-00-9
- Published: 12 June 2006
1 - 50 of 462 results
-
-
Lambda-Rho Processing - A tool to Reveal Full Hydrocarbon Potentials
Authors T. H. Larsen, C. Ojo, S. Gemelli, P. Licalsi and M. AtkinsRegional analysis of a 5,716 well log database from the Gulf of Mexico allows prediction of AVO response, as well as prediction of velocities useful to processing geophysicists. Regional trends are derived from depth profile plots of well sand / shale velocity histograms.
Four major sub-regions were delineated, based on these profiles:
1.Lower and Middle Miocene Shelf,
2.Upper Miocene through Pleistocene Shelf,
3.Upper to Middle Slope, and
4.Lower Slope.
Strong velocity inversion is common in the geopressured Miocene in the deep Lower and Middle Miocene Shelf region. The present deep water areas shows a slower velocity increase with depth throughout the lithologic section than is seen on the shelf above geopressure, but has a much narrower range in variation than is seen on overpressured rocks on the deep shelf. The Lower Slope appears to have a greater spread in sand and shale P-wave velocities than are seen in the Upper to Middle Slope areas.
This analysis also allows prediction of the velocities which should be seen by the processing geophysicist. Some features of the velocity functions seen are those usually associated with multiple reflections, and as such, often discounted by the processor.
-
-
-
AVO and Seismic Processing Implications from a Regional Database of Velocity and Other Acoustic Rock Property Trends
Authors H.R. Nelson, S.D. LeRoy, L.R. Denham, P.J. Desai, M.E. Guthrie and M.A. DunnTo better understand the physical characteristics of sedimentary deposits in Lake Geneva, we acquired and processed very high resolution seismic reflection data. Accurate amplitude measurements were obtained after correction for the frequency response of the hydrophones which were individually calibrated. In a first part, we present the acquisition and the pre-processing done on these data to correct the amplitude. In a second part, we migrate the data using a preserved amplitude pre-stack depth migration, and then apply a post-migration processing in order to correct for residual move-out. Finally, AVA analysis enables to differentiate sedimentary unit boundaries.
-
-
-
AVA Analysis of Very High Resolution Seismic Data for the Study of Sediments in Lake Geneva, Switzerland
Authors D. Hammami, A. Egreteau, F. Marillier and P. ThierryThis paper continues the studies presented in this conference by Loizou et al. (2006), where we have compared the AVO analyses from four wells in the west of Shetland: Foinaven oil well (204/24A-2); Laggan gas well (206/1-2) and two prospect wells (204/17-1 and Assynt 204/18-1). In this study, we apply the spectral decomposition to the data from these four wells and provide further evidence that there are also differences in the spectral characteristics between the four wells. While Foinaven and Laggan Class III AVO anomalies are consistent theoretical predictions for frequency-dependent AVO behaviours. However, the results from the Assynt prospect 204/18-1 and another prospect 204/17-1 show rather complicated behaviour in the iso-frequency sections that cannot be fully explained. In summary, though the amplitude anomalies seen in the two prospects were originally interpreted as to be similar to the Foinaven, but our study indicated they are different in both the AVO behaviour and the spectral characteristics.
-
-
-
AVO Analyses from Four Wells in the West of Shetland - Spectral Decomposition
Authors E. Liu, M. Chapman, N. Loizou and X.Y. LiGeological models are currently used to aid AVO-analysis, usually thick-layered. In an actual thin-layered sub-surface medium, the AVO has some specifics, ignoring which may lead to errors in predicting hydrocarbon reservoirs. In the resonant frequency range periodic thin-layered stack, AVO inversion on the basis of the linearized Shuya formula produces an estimate of the effective Poisson coefficient much lower than one of a separate gas-saturated layer. Also, in the low-frequency range an effective Poisson coefficient estimate is much higher than one in case of a separate gas-saturated layer. Within a frequency range close to the resonant frequency (tuning thickness) for a thin-layered stack, favorable conditions occur for predicting multi-layer hydrocarbon reservoirs from the AVO-analysis. At the same time, disregarding absorption may lead to interpretation errors. A finite difference solution for the elastic wave equation and the Haskell-Thomson method in its visco-elastic variant were used to perform the investigation.
-
-
-
AVO for Pre-Resonant and Resonant Frequency Ranges of a Periodical Thin-Layered Stack
Authors N. Marmalyevskyy, Y. Roganov, A. Kostyukevych and Z. GazarianA new method for computation of seismic AVO attributes such as intercept and gradient, is proposed. By combining detailed sedimentological modeling with well logs, we compute alternative net-to-gross and porosity logs. The method is developed for reservoirs consisting of ultra-thin sand-shale layers, as for instance turbidite reservoirs.
-
-
-
Seismic Modelling from Ultra-Thin Layered Reservoirs
Authors A.M. Stovas and M. LandroAs we are running out of oil, and the oil price is reaching new hights, the oil industry is increasing the focus on exploration and production of heterogeneous reservoirs. In this paper we focus on the rock physics of shaly sands, and how different types of clay configurations will affect the rock stiffness and pore fluid sensitivity.
Laminated sands and shaly sands with pore-filling clays will have different fluid sensitivity. We find that lamination will increase the Vp/Vs ratio for gas saturated sands compared to clean sands, in contrary to sands with pore-filling clay, where the Vp/Vs ratio will be relatively less affected by the clay content. This is related to the reduced shear effect induced by the micro-scale clay lamina.
Next, we study the effect of net-to-gross and scale on fluid sensitivity using the Backus Average method. Here we also observe an increase in Vp/Vs ratio. Gas saturated thin-bedded sands will have Vp/Vs ratios similar to oil-saturated clean, homogeneous sands. This is related to the patchy saturation induced by the geologic heterogeneities. We also study the effect of anisotropy on the fluid sensitivity of heterogeneous reservoirs.
-
-
-
Seismic Fluid Prediction in Heterogeneous Reservoirs
Authors P.A. Avseth, A.J. van Wijngaarden, T.A. Johansen and G. MavkoAs we are running out of oil, and the oil price is reaching new hights, the oil industry is increasing the focus on exploration and production of heterogeneous reservoirs. In this paper we focus on the rock physics of shaly sands, and how different types of clay configurations will affect the rock stiffness and pore fluid sensitivity. Laminated sands and shaly sands with pore-filling clays will have different fluid sensitivity. We find that lamination will increase the Vp/Vs ratio for gas saturated sands compared to clean sands, in contrary to sands with pore-filling clay, where the Vp/Vs ratio will be relatively less affected by the clay content. This is related to the reduced shear effect induced by the micro-scale clay lamina. Next, we study the effect of net-to-gross and scale on fluid sensitivity using the Backus Average method. Here we also observe an increase in Vp/Vs ratio. Gas saturated thin-bedded sands will have Vp/Vs ratios similar to oil-saturated clean, homogeneous sands. This is related to the patchy saturation induced by the geologic heterogeneities. We also study the effect of anisotropy on the fluid sensitivity of heterogeneous reservoirs.
-
-
-
Depth Trend and the Characteristics of PS AVO
By H. XuGonzalez et al. (2003) & Xu et al. (2005) showed the application of PS Elastic impedance (PSEI) for lithology and fluid prediction. To understand the effectiveness of this approach in relation to the target depth it is necessary to analyze the typical characteristics of PS AVO in a compaction trend framework. In this paper we will review the typical depth trend of sand and shale properties in a sedimentary basin and discuss the characteristics of PS AVO in several unique depth zones.
-
-
-
Use of Rock Physics Principles for Inversion of Pre-Stack Seismic Data
Authors A. Mukherjee, H. Xu and N.C. DuttaFull waveform pre-stack inversion of seismic data usually provide a more accurate and reliable estimate of the elastic properties of the earth over conventional AVO analysis, as it can account for the contamination of seismic amplitudes from other wave modes. However as in all other types of inversion pre-stack full waveform inversion is also sensitive to the starting model and other apriori information. Conventionally well logs available in the area are used for this purpose. However, dipole sonic log in most cases is not available due to cost and P-wave sonic and bulk density logs are not available in the shallow parts due to large holes. In this abstract, we present a general rock physics based technique for constructing pseudo logs and then use them to build our initial models for pre-stack waveform inversion of seismic data. The pseudo-shear sonic log calculation is based on the work by Dutta and Wendt (1993). Another set of pseudo-logs are based on mechanical compaction theory and rock physics based velocity porosity relationships. We test inversion results for both the techniques on well log synthetic from deep water Gulf of Mexico.
-
-
-
Physical Modeling of AVO Responses
Authors B.J. Evans, A. Wandler and C. LinkSeismic amplitude versus offset (AVO) methods are a well established practice for the direct indication of hydrocarbons, and are proven using both numerical modeling and field data. However, from a laboratory stand-point, AVO techniques have not to date been demonstrated in practice. This paper presents a first case of a physical model which was used to practically demonstrate the use of AVO for the separation of a hydrocarbon (oil) from pure water or brine. The physical model was also used to demonstrate how AVO cannot be used to separate water from a brine (30,000 ppm NaCl). A test using dissolved CO2 in water showed that an amount of 0.1 mol% was inadequate for seismic detection. The physical model was also used to demonstrate the complexities of the oil/gas/water mix, where it was possible to show how under certain circumstances, gas bubbles can remain trapped between oil and water.
-
-
-
Moveout Stretch Implications for AVO
Authors P.R. Williamson and E. RobeinThe Zoeppritz equations for AVO, and their various approximations, apply strictly to a single isolated interface between two half-spaces. In practice this is almost always not the case, and effects known as AVO tuning are observed due to the apparent change in the time-thickness of beds on recorded traces with offset. While NMO or migration should equalise these time thicknesses across all offsets, the tuning effects are maintained by wavelet stretch. This stretch cannot be meaningfully avoided by 'non-stretch' processing, which simply corresponds to the isolated reflector paradigm. Meaningful AVO analysis, can, however, be achieved by effectively equalising the wavelet across all traces.
-
-
-
Quantitative Calibration of Seismic to Wells and Probabilistic AVO
Authors M.F. Bee, E. Rietsch, D. Pankhurst and J. MagillWe present deterministic and probabilistic methods to quantitatively calibrate pre-stack seismic data to well data before AVO analysis. We then show how to use the calibrated seismic data with probabilistic AVO methods to analyze the prospectivity of a step-out exploration prospect several kilometers away from well control with the goal of identifying and quantifying hydrocarbons.
-
-
-
Identification of Upper Cretaceous Volcanics Using AVO Attributes; Santos Basin, Brazil
Authors S. Klarner, R. Culpan, R. Fontana and B. BankheadThe deposition of the main reservoir unit in the Santos Basin, the fluvial to shallow marine Upper Cretaceous Ilhabela sandstones, took place during a period of active basaltic volcanism. The volcanic rocks have been partly eroded and subsequently deposited in the reservoir. This has been the cause of a complex diagenetic history. The results are locally occurring sandstones with complex lithologies and elastic properties which differ from the basin trend (Klarner et al, 2005). In order to predict and interpret the amplitudes and AVO behaviour of the Ilhabela reservoir it is essential to map the occurrence of the volcanics as well as the transport direction of their erosional products. We make use of the fact that the volcanic related lithologies display a significantly higher Vp/Vs ratio than the embedding clastic sequences. In this paper, an AVO approach is presented which helps to identify volcanic rocks in the section.
-
-
-
Improved Seismic Imaging of Deepwater Turbidite Channels - A Case History from Offshore Angola
Authors S.P. McHugo, M.F. Francis, A. Cooke, N. Woods and J. EnglishExisting seismic data and appraisal drilling in the lower Congo basin show evidence of significant sandstone reservoirs in the tertiary section, formed by deepwater turbidite flows. The challenge is to develop and manage these complex reservoirs. To delineate the reservoirs, it is important to identify the fine details of the geometry of the reservoir sands and locate the structural and stratigraphic trapping mechanisms. The cost of drilling development wells in this area and the complex nature of the reservoirs make reflection seismic data a cost-effective tool in reservoir management. Thickness resolution obtained from existing seismic data in this area is in the order of 19 m A new survey was acquired in 2003 in an effort to obtain higher resolution.
In this paper, we describe the planning, acquisition, and processing results of a high-resolution point-receiver seismic survey. The survey was acquired with the objectives of mapping the thin sand units associated with turbidite sand channels, to provide long offset data not present in the existing data and to assess the benefits of point-receiver acquisition.
Results indicate that the objectives of the project have been met through acquisition and high-fidelity processing of point-receiver seismic data.
-
-
-
Porosity and Shale Volume Estimation for the Ardmore Field Using Extended Elastic Impedance
Authors A.M. Francis and G.J. HicksDeterministic seismic inversion and extended elastic impedance (EEI) have been used to obtain quantitative estimates of porosity and Vshale over the Ardmore Field. The optimum EEI angles corresponding to porosity and Vshale were determined from the well logs, together with a lithology indicator. The prestack seismic data were then projected to the Chi angles corresponding to these three petrophysical indicators and deterministic inversions were performed to obtain three broadband EEI volumes. Three-parameter linear regressions were then performed to estimate quantitative porosity and Vshale volumes from the three EEI volumes. Regions of High porosity and low Vshale have been identified which may suggest possible future drilling locations.
-
-
-
Prediction of Resistivity Using P and S-wave Properties from Prestack Seismic Inversion
Authors H. Xu and N.C. DuttaIn this paper, we study the prediction of resistivity from seismic data, based on resistivity-velocity relationships calibrated from well logs. Previous efforts in this area have included predicting resistivity from seismic amplitude or seismic-derived P-wave velocity. Here we present the prediction of resistivity from both P and S wave properties (P-impedance and Poisson’s ratio), which can be derived from prestack seismic inversion. The results can be used for identification or upgrading prospects in a mature field where resistivity logs are abundant.
-
-
-
The Development of Low Temperature Tem Squid Systems for the Geosciences
By C.L. Le RouxSuper-conducting Quantum Interference Devices (SQUIDs) are tiny sensors that detect and measure very small magnetic fields. As part of an ATD-GRG research project, the Institut für Physikalische Hochtechnologie (IPHT) in Jena, Germany, have developed a Low Temperature SQUID (LTS) ground Transient ElectroMagnetic (TEM) system for Anglo to further strengthen the company’s mineral exploration capabilities. A brief history of the technology development is illustrated with results from various field tests. Early field trials conducted in Germany in 2002 showed good promise, but some system problems. Partial redesign and good applied science led to successful field testing and comparison of LTS, HTS and conventional coil receivers in Sweden in 2003. Further field tests on the Western Australian Nickel belt in 2003 and 2004 proved the system’s field-worthiness and that using liquid Helium as a coolant poses no serious logistical problems even in such a harsh environment. Undisputed proof of superior signal-to-noise capabilities over HTS, Fluxgate and coil sensors was again evident as well as the advantages of using LTS sensors for detecting conductive targets at depth or below conductive cover, hitherto a severely limiting constraint on exploration for conductive ore-bodies. Because of the better S/N stacking time is reduced and production is 4 to 10 times faster depending on the environment. Some spurious system response problems were more prominent during tests in resistive terrains in South Africa, but have subsequently been solved. The LTS TEM SQUID system has now been recognized as a major breakthrough with potential to give Anglo exploration teams a significant strategic advantage over competitors. An agreement has been signed with IPHT that provides Anglo with exclusive rights to the project technology for a ten year period following its development. Three systems are being deployed by our base metal exploration teams in Australia and Canada, while a fourth will be delivered later in 2005 for on-going exciting development work in Southern Africa.
-
-
-
The Interpretation of Potential Field Data Using Continuous Wavelet Transforms
More LessThe continuous wavelet transform has been used with much success in the analysis of non-stationary time series. It has been used much less frequently in the interpretation of magnetic or gravity data, although several approaches have been tried. A simple method of obtaining location and depth estimates of gravity and magnetic field sources is suggested here, For gravity data the method uses wavelets based on the integer-order horizontal derivatives of the gravity anomaly from a point source (the Poisson kernel). For magnetic data the wavelet is based on the integer-order horizontal derivatives of the analytic signal of the anomaly from a step or a horizontal cylinder. The method is compared with Euler deconvolution, and is demonstrated with synthetic models and on gravity and magnetic data from South Africa.
-
-
-
Contributions to the Gravity Field of Southern Africa from Crustal Thickness and Seismic Velocity Variations
Authors S.J. Webb and D.E. JamesAs a result of the Kaapvaal Project we now have unprecedented coverage of the crustal thickness and details of the seismic velocity variations in the tectosphere beneath southern Africa. By using these data and reasonable density relationships we can calculate the contribution of each of these components to the overall gravity field of southern Africa. These gravity modeling results confirm the suggestion that the high seismic velocity keel beneath southern Africa has a lower density than surrounding mantle material and is consequently highly depleted; a result in agreement with the xenolith data obtained from kimberlites. We estimate that the 1% seismic velocity variation observed between on and off craton leads to a 1% variation in mantle density due to compositional variation. This low density keel is vital to counterbalance the effect of the thinner than average crust that is observed beneath the Kaapvaal and Zimbabwe cratons. Thus in regions where the Archaean craton boundaries may not be apparent from geological mapping, seismic studies and gravity modelling could assist with delineating potentially cratonic regions with diamond potential.
-
-
-
New Palaeomagnetic Data from the Main and Upper Zones of the Bushveld Complex
Authors S.A. Letts, T. Torsvik, L. Aswal and S. WebbThe Bushveld Complex (BC) has been the subject of many palaeomagnetic investigations since 1959. Despite these studies, systematic inconstancies have been found between the palaeomagnetic findings and well constrained ages determined for the Bushveld Complex. One concern is the large spread in pole positions previously determined for the different zones of the BC. This has been interpreted in prior studies to indicate that the Bushveld was emplaced and cooled below the Curie temperature of magnetite over a time span of 50 Ma. This inconsistency has prompted the current re-investigation of the palaeomagnetic results.
New palaeomagnetic data collected in the Main and Upper zones of the Eastern and Western limbs of the BC, yielded palaeomagnetic poles that eliminated the spread in the apparent polar wander path. This observation is in agreement with precise age data, constraining the time period of emplacement of the BC. Fold tests applied to each zone yielded statistically positive results supporting a primary magnetic signature and indicate that the complex was intruded in a near horizontal position.
-
-
-
Finding the Edge of Salt Via a Dual-Velocity Flood
Authors J.E. Anderson and C.M. MarcinkovichImaging an overturned salt edge with turning waves often requires large apertures, long recording times and a sediment velocity profile that appropriately increases with depth and that is unobstructed by other salt bodies within the aperture of interest, conditions that may not always be available in practice. In some situations, data that may not meet all of the turning-wave-image criteria can be used to find the salt face via a dual-velocity-model flood technique similar to a vertical-seismic-profile (VSP) proximity survey. In this case, the reflectors that truncate against salt are imaged at their truncation point in the correct position, helping to define the salt face.
-
-
-
How Many Angles Do We Really Need for Delayed-Shot Migration
By J.T. EtgenWhether you can use a sparse set of source angles in delayed-shot migration, or not, depends on how well your actual set of sources approximates (or can be made to approximate) an unaliased “antenna”. If you have a well sampled source antenna, then sparse angles can be used to create high-quality images since you can transform your data into the equivalent delayed-line-source experiment. If your collection of sources does not satisfy this requirement, then you may have to use a large number of angles to construct artifact-free images.
-
-
-
Measuring Reservoir Compaction Using Time-Lapse Timeshifts
Authors P.J. Hatchell and S.J. BourneTime-lapse timeshifts refer to the differences in two-way seismic travel times that are frequently observed in the analysis of time-lapse seismic surveys. One source of timeshifts originates inside the reservoir interval as a result of changes in the pore-fluid properties that alter the seismic velocity. Another is from changes in seismic velocity and layer thickness that occur both inside and outside of the reservoir as a result of reservoir compaction and stress and strain redistribution in the surrounding formations. Timeshifts induced by changes in fluid properties are always zero above the top reservoir reflection event and constant below the base of the reservoir. These fluidinduced timeshifts can be significant (for example, when gas is released as an oil passes through bubble point) and are routinely calculated using Gassmann or similar theories and are not the focus of this paper. The compaction-induced timeshifts have opposite gradients on the inside and outside of the reservoir. Within the reservoir, the reduction in layer thickness and the expected increase in seismic velocity will reduce the seismic travel time across these layers. Outside the reservoir, the decrease in reservoir thickness is exactly balanced by surface subsidence and rock expansion. The expanding overburden produces increased layer thickness and slower seismic velocities that increase the seismic travel times. Observations on real time-lapse seismic data over compacting reservoirs show that the positive timeshifts that accrue in the overburden are larger than the negative timeshifts that accrue inside the reservoir (the sign convention chosen is that positive timeshifts result when the seismic travel time increases). The amount of overburden elongation cannot exceed the amount of reservoir compaction. So if the change in velocity were simply proportional to the change in vertical strain, the reduction in travel time through the reservoir would exceed the increase in travel time though the overburden. The net effect would be a negative timeshift below the reservoir. Instead positive timeshifts are observed below compacting reservoir indicting velocity reduction per unit elongation strain significantly exceeds the velocity increase per unit contraction strain. Using simple models of the velocity-strain response it is shown that time-lapse timeshifts are proportional to the stretching of the overburden layers and that this is highly correlated with the reservoir compaction. The net result is that time-lapse timeshifts are a good measurement of the reservoir compaction.
-
-
-
Definition of Depositional Geological Elements in Deep-Water Minibasins of the Gulf of Mexico Using Spectral Decomposition in Depth Domain
Authors R.H. Tatham, P. Montoya, W. Fisher, R. Steel and M. HudecSubmarine channels, large scours, distributary channel-lobe complexes, turbidite fan complexes and many other components of deep water depositional systems in the central Gulf of Mexico were successfully imaged and mapped using spectral decomposition in the depth domain. When this powerful tool is applied along an interpreted seismic horizon, a better definition of stratigraphic architecture is obtained.
-
-
-
Natural Perturbations of Shared Earth Models
More LessNatural Perturbations of Shared Earth Models (SEMs) are introduced and demonstrated. SEMs, such as the Compound models developed at Norsk Hydro, contain representations of natural geological entities (compartments, formations, fluids, (geo)logical rules etc). Natural Perturbation of the entities (deformation, translation, rotation etc.) can be performed involving only very few degrees of freedom. Perturbations, exemplified in the paper, are run individually, in series or parallel. A special entity within the Compound model (the perturbation structure) holds the order of the Natural Perturbations to be evaluated and can therefore be used in (global and joint) automatic optimization.
-
-
-
Geostatistical Impedance Simulation after Prestack Depth Migration
Authors F. Schaub, A. Egreteau, P. Thierry and H. BeucherConventional reservoir characterization using geostatistical techniques to compute facies and porosity distribution usually begins from an estimation of the acoustic impedance. This impedance distribution is obtained using inversion technique as the stratigraphic inversion which works on prestack reflection seismic data [Tonellot & al., 2001]. The aim of this work is to take advantage of Amplitude versus Angle (AVA) inversion done after prestack depth migration to perform a depth domain impedance estimation constrained by AVA attributes. We propose to use geostatistical impedance simulation constrained by the migrated common image gather (CiG) and the skeleton of the structure obtained during the AVA inversion as well as the intercept and the slope sections.
-
-
-
Neural Modelling of Core Permeability Data
Authors R.K. Fruhwirth and G. MaierIn this paper we show a neural network based method to develop a relationship between core permeability data and a set of other well logs to complete permeability information in well areas that do not contain that information. As an alternative to the common multi layer perceptron we use a special network architecture that has several advantages in approaching the optimal network size. In combination with parallel learning, automatic network growing and sophisticated stopping criteria that architecture allows an efficient and robust estimation of the optimal network for a particular problem. We use resistivity, gamma-ray, density, neutron porosity and the p-wave sonic logs as model input yielding a heuristic permeability model that allows completion of information in the area of interest yielding a synthetic permeability log. In addition convolutional network input in combination with principal component transform enhances the quality of the resulting model.
-
-
-
Methodology for Integration of Small Scale 3D/4D Seismic Features in Reservoir Simulations
Authors N. Hadj Kacem, P. Berthet, F. Pivot and P. SamierGeological modelling of depositional facies and petrophysics is usually performed with a high vertical resolution and a low lateral resolution due to flow simulation constraints. The 3D/4D seismic may bring a high lateral resolution on reservoir characterization. To handle this fine scale information, the geological modelling requires a direct integration of well and seismic information. The lateral fine scale details of some good quality seismic attributes allow to locate small and meaningful reservoir connectivity. The deterministic method of integration, presented here, preserves seismic connectivity into the flow reservoir model. The method also offers a permanent link from seismic/geologic information to dynamic model. As soon as small heterogeneity is properly transferred into the flow model, the great benefit of this method is to reduce the history matching phase and to ensure more predictive dynamic model. In this paper, we illustrate a three step methodology allowing an automatic integration of geologically coherent seismic information within the reservoir model.
-
-
-
The EU Research Strategy for Zero Emission Fossil Fuel Conversion
By P. DechampThe research strategy put in place by the Directorate General for Research of the European Commission in the field of the mitigation of CO2 emissions is first placed in the general context of the Commission energy policies. These actions are addressing the climate change issue, the introduction of renewable energy sources, the security of energy supply, the promotion of energy efficiency and the opening of energy markets.
The research policy of the Commission is mainly the European Research Area concept and its number one instrument, the Framework Programmes for research and technological development. The rational and the analysis supporting the ERA will be covered, as well as the structure and the new implementation modalities of the Framework Programme. Initial ideas for the 7th framework programme covering the years 2006-2013 will be debated.
CO2 capture and sequestration projects are organised to fit into the above-mentioned research policy, while contributing to the successful deployment of the Commission energy policies. These projects represent a portfolio of the order of 140 m€ of research and technological development.
Future perspectives, in particular in view of initiatives in the international arena and the Zero Emission Power Technology Platform, are finally outlined, addressing the need for an integrated European approach to develop and demonstrate CO2 capture and storage technologies for the benefit of the European citizens, industry and society.
-
-
-
The ReMoVe project; Can We Guarantee Long Term Safety of Geological Storage of CO2
By E. ElewautSince 1990, Europe and the European Commission have invested a huge amount of research in the geological storage of CO2, The aim was initially to create an inventory of potential storage sites and volumes, later to build models to study the subsurface behavior of CO2 and the storage matrix and to forecast possible problems, later still to perform risks analysis at all relevant time scales.
Since Statoil started injecting CO2 on an industrial scale off-shore Norway in 1996, the focus has shifted to the monitoring of geological storage. Over the last ten years, experience has been acquired with both large scale projects (Sleipner, Norway; Weyburn, Canada) and more limited in scope, so called “subsurface laboratories” in Germany, The Netherlands and Poland. Two new geological storage projects (In Salah, Algeria and Snøhvit, Norway) now provide the opportunity to build on this work.
The CO2ReMoVe project started on 1 March 2006. It is being carried out under the umbrella and with the support of the European Commission’s Sixth Framework Programme for Research and Technology Development.
For five years, 30 partners from 12 different countries all over the world will invest EUR 15 million in an effort to bring together all relevant research and industry experience and know how in the field of underground storage of carbon dioxide.
The consortium of industrial, research and service organizations proposes a range of monitoring techniques, applied over an integrated portfolio of storage sites in order to develop:
1. methods for base-line site evaluation;
2. new tools for monitoring storage and possible well and surface leakage;
3. new tools to predict and model long term storage behavior and risks;
4. a rigorous risk assessment methodology for a variety of sites and time scales;
5. Guidelines for best practice for the industry, policy makers and regulators.
The recommendations from these international efforts will form an important step towards a worldwide consensus in licensing and certification of the storage activities in a number of geological media. These will include oil and gas reservoirs, coal seams and aquifers.
It can be expected that the project will achieve a better understanding with the policy makers and the public that CO2 can be safely transported and stored in the subsurface and that this storage can at all times be safely monitored. The project will also provide the assurance required for geologically stored CO2 to qualify for credits under the emissions trading mechanism.
It can be expected that the project will lead to greater understanding among policy-makers and the public that CO2 can be safely transported and stored in the subsurface, and that this storage can be safely monitored at all times the project will also provide the assurance required for geologically stored CO2 to qualify for credits under the emissions trading mechanism.
-
-
-
Climate Change – The Challenge of the 21st Century
By K. RadunskyIssues to be addressed by the presentation:
- Energy scenarios by the International Energy Agency: Business as usual scenario, scenario with enhanced energy efficiency, scenario with additional carbon capture and storage;
- Possible impacts of climate change, worldwide and in Austria: temperature change, cryosphere, hydrology and water resources, terrestrial biological systems (including agriculture and forestry), human health, disasters and hazards;
- Policy responses
· The UNFCCC: its ultimate objective
· The Kyoto Protocol: its added value
· The European Union: its current position on climate change as reflected in council conclusions
· Processes started in Montreal in 2005
o Process linked to Article 3.9 Kyoto Protocol
o Dialogue under the Convention
- Elements of a possible future architecture: Outcome of the Climate Dialogue at Pocantico
- Carbon capture and storage
· Potential contribution: based on the Special report of the IPCC
· Issues for further consideration: based on the outcome of SBSTA24
- The timing challenge: based on recent scientific results (PIK)
-
-
-
Controlled Source Electromagnetic Imaging in Shallow Water - A Case Study
Authors D. Andreis, L. MacGregor, J. Tomlinson and N. BarkerCSEM surveys have been used successfully in a variety of settings including West Africa, Southeast Asia, The Gulf of Mexico and the North Atlantic. Early surveys concentrated on deepwater areas. However they represent only a small proportion of potential exploration targets. In particular to date the method has been limited to relatively deep water (300m or more). This is because in shallow water, signals that have interacted with the air can have a severe impact on the recorded signals and can dominate the response. This noise (known as the 'airwave') dominates the CSEM response at source-receiver offsets which are sensitive to resistivity structure at the likely range of depths of hydrocarbon reservoirs. Researchers at OHM have been working on extending the operating envelope of the CSEM method into progressively shallower water. The approach adopted centres on characterising the physics behind the airwave phenomenon, and then using this knowledge to design approaches to data acquisition and processing that mitigate its effect. As with many geophysical problems, there is unlikely to be one silver bullet that will solve the 'airwave' problem in all circumstances, and so a range of concepts were investigated.
-
-
-
Shell's Controlled Source EM Results Show Positive Impact
Authors D.J. Smit, S. Saleh, M. Costello, J. Voon and J. MoserIn this paper an overview will presented of the use of so-called Controlled Source Electro-Magnetic (CSEM) data acquired in deep water areas. Various results in different geologiocal settings will be used to illustrate its impact on a global exploration portfolio. We conlclude with a discussion on some future developments.
-
-
-
A Fast and Rigorous 3D Inversion of the Marine CSEM Data
Authors M.S. Zhdanov and A. GribenkoMarine controlled source electromagnetic (MCSEM) surveys have become an important part of the offshore petroleum exploration. However, due to enormous computational difficulties of the full 3-D inversion, the practical interpretation of the MCSEM data is still based on qualitative analysis and relatively simple 2-D geoelectrical models of the sea-bottom structures. In this paper we present a new approach to 3-D inversion of the MCSEM data. It is based on the rigorous integral equation (IE) forward modeling and a new IE representation of the sensitivity (Frechet derivative matrix) of the observed data to the variations of the sea-bottom conductivity. This approach requires just one forward modeling on every iteration of the regularized gradient type inversion algorithm, which speeds up the computations significantly. We also use a regularized focusing inversion method, which provides a sharp boundary image of the petroleum reservoir. The methodology is tested on a 3-D inversion of the synthetic EM data representing a typical MCSEM survey conducted for offshore petroleum exploration.
-
-
-
Anisotropic Depth Migration of Marine Controlled-Source Electromagnetic Data
Authors K. Hokstad and T. RøstenWe present a transversely isotropic depth migration scheme for marine controlled-source electromagnetic (MCSEM) data, based on Claerbout's well-known 45 degree equation from seismic imaging. The proposed scheme is applicable to MCSEM data acquired with a 2-D geometry, and is numerically very efficient. We show examples from field data acquired offshore Norway.
-
-
-
Contribution to Oil Exploration and Development - A Successful Inductive Multi-Frequency EM Survey On-Shore Brazil
Authors C.A. Dias, O.A.L. de Lima, H.K. Sato and J.A.C. MoraesIn this work we discuss the results of an experimental study performed using a multi-frequency electromagnetic method over a mature oil field in Recôncavo basin, Bahia-Brazil. Five 1.8 km transects, 200 m apart, were surveyed over a selected oil reservoir block. The processed EM data are represented as cross-sections and maps of apparent resistivity and induced polarization parameter, using a consistent plotting procedure. All the sections, controlled by well logging data, allow to recognize the following geological features: (i) the oil sandstone horizons and their trapping shales; (ii) the oil-water interface and some zones of water invasion; and (iii) lateral electric contrasts representing fault zones. These results suggest the real possibility of the use of the spectral EM method in the direct detection of hydrocarbons, as well as for monitoring the efficiency of the artificial fluid injection used for secondary recovery. Also, this experiment brings about a further development in the inductive measurement of IP and introduces, for the first time, the use of this property in oil reservoir exploration and characterization.
-
-
-
A 3D Near-Wellbore Imaging Algorithm for Triaxial Induction Data
Authors A. Abubakar and T.M. HabashyWe present a rigorous nonlinear inversion method for the three-dimensional (3D) imaging of the near-wellbore region employing multi-array triaxial induction data. The method used is the so-called Multiplicative-Regularized Contrast Source Inversion
(MR-CSI) method. There are two main features of this method. The first is that the method does not require the explicit solution of the full forward problem at each iteration step. The second is that the regularizer is included as a multiplicative constraint that allows the automatic and adaptive determination of the regularization parameter. These two features enable us to robustly solve an inverse problem with 65,536 unknowns using a single-processor present-day computer power.
-
-
-
Inversion of Multi-Transient Electromagnetic (MTEM) Data
Authors B.A. Hobbs, G. Li, C. Clarke and J. LinfootThe multi-transient electromagnetic (MTEM) technique, for detecting and monitoring hydrocarbons, works by injecting a transient current into the ground (a source) and recording the potential difference between two receiver electrodes (the receiver) some distance, or offset, from the source. Field layout is similar to that of seismics, with many receivers per source and many sources per profile. After processing, the data for each source-receiver pair consist of the earth’s impulse response function and step response function. Two methods of inversion are described in this paper. The first uses a single value from each step response (the late time value) and transforms this to an apparent resistivity. These apparent resistivities are inverted in a 2D scheme to give a cross-section of resistivity versus depth. In the second method the full waveforms of either the step or the impulse response functions, are inverted simultaneously for several offsets at each common mid-point position. The resulting 1D resistivity models are collated to form a 2D resistivity image of the subsurface. The methods are illustrated with data from a demonstration survey over a gas storage reservoir.
-
-
-
Fracture Imaging in Weathered Granitic Quarries Using GPR Data
Authors M.A.B.B. Barsottelli-Botelho and M.H. HeimerWe study a granite rock quarry, partially covered by a weathering cap, situated at the State of Bahia (Brazil). The aim was to understand the spatial distribution of fracture surfaces inside the rock and distinguish quickly intact marketable granite areas in order to improve quarry management. To interpret the real data, we use a finite-difference scheme to simulate 2D ground penetrating radar data by solving the damped wave equation. The synthetic GPR sections reveals how a conductive clayey overburden (20 mS/m) masks the real position of the fractures in the granite. The algorithm shows clearly the increase in attenuation with the increase of the frequency, and also with the thickness increase of the weathering cover; which is also responsible for the pull-down effect on reflectors below. The results of the modeling have a good agreement with the actual data.
-
-
-
Normalized ElectroMagnetic Imaging (NEMI) for Controlled Source EM Evaluation of Hydrocarbon Prospects
Authors E.C. Morris, M.C. Sinha, L.M. MacGregor and D.W. OldenburgMarine Controlled Source ElectroMagnetic (CSEM) surveying is a powerful tool for mapping offshore electrical resistivity structure and in recent years has been developed as a DHI tool. Geophysical inversion and forward modeling are currently the standard methods of CSEM data analysis. However, due to non-linearity of the problem, these methods are computationally time intensive. We present a technique for fast imaging of thin resistive layers within a conductive background that enables a ‘first look’ at full CSEM datasets before imaging. The non-linear properties of the electromagnetic fields are used to determine the existence and lateral extent of thin resistive layers that may be associated with hydrocarbon-bearing layers. We present the results of synthetic datasets that show the imaging algorithm is successful at identifying the existence and lateral extent of a hydrocarbon bearing layer.
-
-
-
Modelling Study of Airwave Contribution to the CSEM Signal
By K.N. MadsenThe Controlled Source Electromagnetic (CSEM) signal received in a three layer model (air, sea and seabed) has been split into contributions from the direct wave, the signal travelling through the seabed and the direct and indirect airwave by means of three modified models run in addition to the full three layer model. The components have been split for various cases of sea depth, seabed resistivity and frequency. The results show that the contribution from the indirect airwave is of the same order of magnitude as the contribution from the direct airwave and may be even larger. It is also shown that the relationship between the airwave and the signal that has travelled through the seabed is very different depending on whether the seabed resistivity is low or high. This may influence the choice of frequency for a CSEM survey.
-
-
-
Accuracy of Sharp Inversion of CSEM Data Constrained by Seismic
More LessIt is well known that sharp inversion of CSEM data constrained by seismic can produce very accurate resistivity estimation. However frequently asked questions are: is the inversion result still valid if the depth and the thickness of the layers estimated from seismic interpretation are affected by some inaccuracy? How this inaccurate depth/thickness estimation propagates through the inversion of the CSEM data? In this paper we try to answer these key questions through synthetic tests and with application to real data where a well control exists.
-
-
-
AEM Combined with TDEM - A Good Tool for Mapping the Quaternary in Rugged Areas
More LessOverdeepend alpine valleys are main players in alpine geology, and therefore the main operational theatre for applied geophysicst in Austria. One of the main geological questions to be tackled is the presence and/or size of hydrogeological regimes, mostly harboured in quaternary units. The combination of Air-borne electromagnetics (AEM) and transient-electromagnetics (TDEM) proofed successful as assistance for geological mapping activities in rugged, alpine areas. Hereby the TDEM method is applied to collect deeper information than provides by air-borne systems. The starting models for TDEM inversions are constraint by multi-electrode geoelectric profiles. However, strong anthropogenic noise in alpine valleys reduces the success rate of TDEM surveys to 70%. One case study is presented, showing the thinning out of a clay rich bottom set underneath a glacial terrace.
-
-
-
Improving Signal-to-Noise Ratio Using Pseudo Random Binary Sequences in Multi Transient Electromagnetic (MTEM) Data
Authors D. Wright, A. Ziolkowski and G. HallWe present multi-transient electro-magnetic (MTEM) data using a step-function and a pseudo-random binary sequence (PRBS) as the source time function. We may recover the earth impulse response from either data set and integrate the result to obtain the corresponding step response. Results show that the PRBS waveform recovers the same result as the step in current but in a much shorter time.
-
-
-
Modeling Responses of a Wide-Band Drill-Hole FEM Receiver
More LessResults from numerical modeling of a eletromagnetic drill-hole probe SAMPO are presented. The modeled quantities are in-phase, quadrature, amplitude and phase of the axial components of the magnetic field. All quantities are normalized by the value of the reference field. The model used in this study is a thin plate model. The results of modeling are also compared with field data. The interpretation rules derived from numerical modeling were found to be in good agreement with the field data.
-
-
-
Magnetotelluric Study along a Profile Traversing the Korean Peninsula
More LessMagnetotelluric measurements were carried out along a profile traversing the Korean peninsula, which is an important tectonic link between the continental block of China and the island arcs of Japan, to figure out the mid-crustal structure of electrical conductivity. The 2-D inversion result shows a few highly conductive anomalies and highly resistive anomalies. The highly conductive anomalies are related with the basement rocks of the Cretaceous Kyongsang basin and the sedimentary and metamorphic rocks of the Okchon belt that is a representative orogenic belt in the Korean peninsula, while the highly resistive anomalies are connected with the Cretaceous granite intrusions in the middle part of the Okchon belt and the eastern part of the Kyongsang basin. Another interesting feature is the large phase anomaly exceeding 90° in the Okchon belt. Although a reliable explanation seems to be made by an electrically anisotropic structure, it will be necessary to treat a full 3-D modeling or an anisotropic modeling to understand the complex structure of this region.
-
-
-
Structure of Flysch Cover as a Result of Detailed and Semi-Detailed MT Survey
Authors M. Wojdyla, M. Stefaniuk, T. Czerwinski and A. Maksymlish Carpathians where the efficiency of reflection seismic survey is poor as a result of complex structure of the flysch cover of the Carpathian overthrust. The main aims of the surveys were recognition of Carpathians structure, but results of them were applied to studying structure and lithological differenciation of flysch cover. The meseurements were applied in two variants. First, MT sites were located separately along profile line with a step 1–3 km. In each sounding site short, 400 m continuous profiling was carried out to eliminate effects of small near-surface resistivity inhomogenities. Second, long (up to 15 km) magnetotelluric continuous profiling was carried out as an EMAP method. The quantitative interpretation was based on 1D Occam inversion and 2D NLCG algorithm. The 1D interpretation based on the least-square inversion was made too. An initial model for LSQ inversion was created based on available geological data and results of other geophysical methods. There were two ways of recognizing resistivity of flysch cover during interpretation. The first one is using the EMAP algorithm, the second one - using 2D inversion. A combination of those two methods gives good geoelectrical model.
-
-
-
NL Oil and Gas Portal - Your Gateway to Dutch E&P Data
Authors A.T. Ganzeveld, M.R.H.E. Peersmann, G. Remmelts and R.R.L. AllardSince the 1990's TNO has developed POSC-related E&P data repositories. As of 1997, the Dutch government commissioned TNO to develop a national data repository for all geological data of the Netherlands: DINO. In 2001, the first online interface on that database was launched, called DINOShop. The reliability as well as the vast amount of data contained in the DINO system resulted in a steady growing number of customers and system use, improving the overall quality of data and interface.
In order to endure oil and gas production in the Netherlands, the Dutch government tries to endorse independent operators to work in the Dutch area, offshore and onshore. To emphasize the meaning of this policy, the government wants to give new players a head start: effective regulatory framework and efficient licensing procedures, good infrastructure and easy access to E&P data. In Q4 of 2005, a start was made to create a DINO-driven portal dedicated to the oil and gas industry, the NL Oil and Gas Portal. Not only is the portal a gateway to all E&P related data, it contains petroleum province reference information (in a geological atlas) and gives access to interactive stratigraphic maps, profiles and 3D models.
-
-
-
Integrating Scalable Vector Graphics (SVG) in a Web-Based Seismic Data Portal
More LessAn integrated web-based seismic data portal can effectively support collaborative research in the field of geophysics. In this context, user-perceived performance and usability of the system is of paramount importance. New technologies such as Scalable Vector Graphics (SVG) can improve user interaction, but need to be exploited in a judicious manner. Scope, difficulties and necessary paradigm shifts are considered from the experience of integrating SVG in an open-source web-based seismic data portal.
-
-
-
Vertical Seismic Pitfalls - Problems in Archiving VSP Data
By E.L. JackVSP (Vertical Seismic Profile) data are the poor relation of the oil exploration industry. They are neither fish nor fowl, neither simply well log data nor simply seismic and because they do not easily fit into a database set up for either of their more famous cousins, they can prove troublesome to archive, or at least troublesome to archive in their entirety. This paper describes some of the problems attached to the archiving of VSP data, by examining the variety of data (calibrated logs, velocity tables and reports, in addition to the seismic data) involved in a VSP archive. The particular problems inherent in the various data types are addressed, with special attention given to the seismic data. A recent feasibility study on loading VSP Data to the Common Data Access (CDA) DataStore is described, with an analysis of some of the problems encountered. Finally recommendations are made for archive procedures and for the media most suited to allow access to all aspects of the VSP.
-