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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
121 - 140 of 462 results
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Flow-Induced Noise in Fiber-Optic 3C Seismic Sensors for Permanent Tubing-Conveyed Installations
Authors S. Knudsen, G. B. Havsgård, A. Berg and T. BostickThis paper report the test results acquired of flow induced noise in a fiber-optic 3-C seismic station, where the tests represents some of the possible conditions that may be expected in flowing wells. The tests were performed to evaluate a fiber-optic sensor tool for tubing-conveyed installations in a controlled-flow test facility. The results of these tests demonstrated that the active-coupled 3-C fiber-optic seismic station installed on production tubing inside cemented well casing was capable of detecting very small seismic signals at high single-phase flow rates for frequencies in the 10-600 Hz band. Test results also demonstrated that the active 3-C station has a very efficient decoupling from flow-induced noise (compared to a passive 3-C seismic station directly attached to the production tubing), while at the same time having good coupling to the casing and formation. Test results showed that two-phase flow increased the noise at high frequencies over that of single-phase flow; however, for frequencies <100 Hz the noise increase is small. This testing indicates the potential to acquire high-resolution, multi-component seismic data in flowing wells under certain conditions with fiber-optic sensors.
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Change in Horizontal Stress in Soil from Changing Shear Wave Velocity - A Laboratory Investigation
By R. GhoseWe performed a new experiment on an unconsolidated sand sample in a biaxial pressure chamber to observe the effect of horizontal stress on seismic shear-wave velocity. Multi-offset seismic reception was successfully implemented in the laboratory scale. From changes in shear-wave moveout velocity observed in a receiver array we could distinguish the effect of horizontal stress change. The approach appears to be realisable in field with multi-receiver seismic CPT. This should lead to a new methodology for in-situ monitoring of horizontal stress change in soil. Further, we found a good match between the observed and the modelled shear-wave velocity change as a function of horizontal stress. This observation reinforces the possibility of implementing the model-based integration of seismic and CPT data, proposed earlier, for obtaining unique estimates of in-situ porosity and horizontal stress.
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Source Signature Estimation - Attenuation of the Seafloor Reflection Error in Shallow Water
Authors J. F. Hopperstad and R. LawsZiolkowski et al. (1982) presented a method for computing the monopole pressure field - the notional source signature - of each airgun or airgun cluster in an array from a set of near-field hydrophone measurements. The notional source signatures are then used to compute the far-field signature of the source array. In areas where the seafloor is hard or in shallow water, the seafloor reflection can cause reverberations of significant amplitude in the near-field measurements. Left uncorrected, the seafloor reflections may lead to a significant error in the far-field signature. Kragh et al. (2000) used an adaptive beamformer to remove these reflections. However, in water depths shallower than about 40 m, an alternative method is required. In this paper, we present an extension to the notional source method of Ziolkowski et al. (1982) that includes the water column reverberations measured by the near-field hydrophones in very shallow water.
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Multiple Removal in the Inverse Data Space
Authors D. J. Verschuur and A. J. BerkhoutIn practice, the data of a seismic survey is always discrete. Therefore, seismic data of a complete survey can be conveniently arranged in a so-called data matrix (P). After removing waves that have travelled along the surface (part of the preprocessing step), the data matrix contains signals that can be expressed in terms of wavefield operators describing propagation and reflection in the subsurface.
Considering the dominant role of multiple scattering in seismic data, it is proposed to replace data matrix P by its inverse P-1 before starting seismic processing. In the inverse data space, a natural separation between primaries and multiples occurs, leading to a new type of multiple removal algorithm.
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Partnership in Gas Production and Processing as a Solution for a Marginal Field
Authors G. Palasthy, L. Benedek, L. Erdos, I. Mader, D. Babic and L. Farkas VisontaiC025 Partnership in Gas Production and Processing as a Solution for a Marginal Field G. Palasthy* (MOL Plc.) L. Benedek (MOL Plc.) L. Erdos (MOL Plc.) I. Mader (INA) D. Babic (INA) & L. Farkas Visontai (INA) SUMMARY In 1994 MOL plc. discovered the Vízvár–North gas condensate field in Hungary near to the Croatian border. In the appraisal phase two gas wells were drilled and tested. The composition of the gas is not too advantageous because the CO2 and nitrogen content is high (above 25%) and the condensate has paraffinic behaviour. These circumstances cause technical challenges in the process of
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Experimental & Numerical Investigation of Cap. Press. Hysteresis on Iranian Carbonate Rock
Authors S. M. Hashemi, H. Karimaie, M. R. Esfahani and J. RoodsazC027 Experimental & Numerical Investigation of Cap. Press. Hyst on Iranian Carbonate Rock S.M. Hashemi* (National Iranian Oil Co.-RIPI) H. Karimaie (Norwegia Tech Trondheim (NTNU)) M.R. Esfahani (National Iranian Oil Co.-RIP (National Iranian Oil Co.-RIPI) SUMMARY In this study several experiments were performed on an Iranian carb rock. The bounding imbibition and drainage capillary pressure and sc were determined using a novel experimental setup at high temperat highly accurate measurements of capillary pressure hysteresis on a w show that there is significant hysteresis in capillary pressure bet imbibition curves. Killough and Tan models representing capillary pre based on saturation history
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Increased Gas Recovery by High-Angle Subsea Wells in High-Pressure-High-Temperature (HPHT) Environment at Kristin Field
Authors T. T. Blekastad and O. R. HansenThe Kristin Field is the most extreme high-pressure-high-temperature (HPHT) field in Norway, with a reservoir pressure of 911 bars and a temperature of 175°C. This has led to huge challenges in developing the Field.
The production wells were initially planned as medium inclined wells due to well control issues. Towards field development, strong indications showed that the permeability in the uppermost reservoir was less prosperous than predicted. This would imply only half of the production plateau period committed, reduced recovery from the Field and a substantial deficit in project net-present-value as a result. The need for longer reservoir sections became quite evident.
The scope was extended to near horizontal well designs. The ultimate Kristin well is 6580 m MD long with an 8½" HPHT section of 1083 m with 746 m above 80°. This is the world’s longest and most deviated HPHT subsea gas producer.
By production start 3 November 2005, Kristin has drilled 9 and completed 4 wells, most being high angle wells above 75°. The production simulations show that the plateau production is back up to the original commitments.
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Acid Clathrates for Well Stimulation
Authors V. A. Kuvshinov, L. K. Altunina, A. A. Lobanova and R. K. ShakurovThe paper presents the results of laboratory and field researches of the developed in Russia solid acid reagent - netrol.
From chemical viewpoint netrol is a solid compound of carbamide clathrate and a mixture of inorganic acids. The main part of acid mixture is constituted by nitric acid, which intensifies the effect of acid treatment due to oxidizing ability. Carbamide is a clathrate former and in the netrol solution it provides low interfacial tension, increased detergency and effective penetration, as well as compatibility with water of high salinity. Netrol also includes phosphoric and borohydrofluoric acids, providing stability of a solid netrol form, prolonged effect of acid treatment of the netrol solution and its ability to dissolve silica minerals of rock matrix.
As compared with well-known hydrochloric acid the netrol solution has more effective penetration, especially in mudded carbonate and terrigenous reservoirs with viscous, highly paraffinic and highly resinous oil. It is also compatible with formation waters of high salinity. The netrol solution is easily producible and safe to handle.
In 2004-2005 bottomhole zones of the production and injection wells in carbonate and terrigenous low-permeable reservoirs in Russia and Kazakhstan oilfields were successfully treated with netrol solutions.
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When Geology Meets Geophysics - Optimized Lithoseismic Facies Cubes for Reservoir Needs
Authors P. Breton and O. D. DUPLANTIERWe here present a new strategy for seismic facies probability cubes creation calibrated on petrophysical data. This methodology has been developed on the deep offshore Angola Girassol field data. It proposes to be more consistent with the petrophysical data and to ensure a better geological facies organization and continuity than classical approaches.
In order to infill a geomodel based on seismic constraints, lithoseismic cubes must be fully consistent with the geological interpretation and the petrophysical context. The link between seismic facies probability cubes and the geology is done through the Facies Groups definition. A Facies Group is defined as an interpreted 'log facies classification'. Their definition represents a key stage.
The methodology developed in this paper consists in applying an iterative process between Facies Groups design, their corresponding petrophysical range and seismic response. This new workflow enables to compute optimized lithoseismic cubes as they are fully calibrated on petrophysical data and based on the finest Facies Groups discrimination related to the seismic resolution. The resulting lithoseismic cubes present a much more coherent geological facies organization inside the reservoir model. They provide more suitable data for quantitative estimation of the uncertainties related to the reservoir properties.
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New Approch for Modeling of Two-Phase Flow through Anisotropic Porous Media
Authors V. V. Kadet, N. M. Dmitriev and M. N. DmtrievA new presentation of tensors of relative phase permeabilities for anisotropic porous media is considered.
The relation between the tensors of absolute and phase permeabilities is supposed to be represented by a tensor of 4th rank.
It is shown that in this case the relative phase permeabilities depend not only on the saturation, but also on the ratios of major values of an absolute permeability tensor. The obtained relations for phase permeabilities are used for analyzing the results of numerical modeling of two-phase flow in the orthotropic porous medium. The versions of complex studies for obtaining phase permeabilities in anisotropic porous media from the results of laboratory measurements are discussed.
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Dependence of Elastic Modules on Pore Pressure in Microinhomogeneous Medium
More LessThe paper is devoted to calculation of average elastic modules of microinhomogeneous medium. The new method, which is presented, is based on long-wave approximation, potential method of elasticity and averaging of medium parameters on orientation of structure. The using of fundamental solution of third kind (Weyl H.) as Green tensor gives a possibility to solve regular integral equations instead of singular ones. Velocities of P and S waves are increases with increasing of pore pressure, but increasing of S waves velocities is much more significant with respect to P ones, hence the ratio Vs/Vp is also increases.
Key words. Microinhomogeneity, microstructure, pore space, boundary integral equations.
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Irregular Sampling and Seismic Imaging
Authors H. Keers, T. Standley and A. KaniaMany seismic processing techniques require integration of the data. This integration is commonly done using a binning technique. Binning techniques work well if the integration grid is regular. In practice, however, this is often not the case. We describe an alternative integration technique that takes irregular sampling into account, by assigning weights to the integration points. The weights are computed by triangulating the integration domain.
The two algorithms were tested on a synthetic dataset and a marine dataset from the Gulf of Mexico. The irregular imaging gives better results than the binning method in the cross line direction: acquisition footprints are reduced, resulting in clearer images. In the inline direction there is not much difference between the two methods. Since the irregular imaging algorithm is easy to implement and the additional CPU is negligible, it is an attractive alternative to binning.
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Interpolation of Near Offsets with Multiples and Prediction-Error Filters
Authors W. J. Curry and G. ShanInterpolation of near offsets is an important issue in marine surveys. Pseudo-primary data is created from the Sigsbee 2B model using surface-consistent cross-correlation. This creates pseudo-data in near offsets that were missing from the original data. A non-stationary prediction-error filter is estimated on the pseudo-primaries, and is used to interpolate the missing near offsets in the original data, with promising results. The prediction-error filter can also be used to gauge the benefit of the pseudo-primaries by convolving it with the recorded data.
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Wide Azimuth Interpolation
Authors D. Trad, J. Deere and S. CheadleSeismic processing techniques, such as migration, have strict requirements on information content in the input seismic data. Although not a substitute for well-sampled field data, interpolation can provide useful data preconditioning that allows migration to work better.
Seismic data interpolation has been around for long time, but only recently have we been able to use complex multidimensional and global algorithms that have the capability to infill large gaps in 3D land surveys. This innovation offers great potential for improvement, but for this technology to become useful, many questions still need answers. What are the best domains in which to interpolate? What is the optimal size of operators given a particular level of structural complexity? Should we pursue an ideal geometry for migration or should we stay close to the input geometry in order to minimize distortions? How does sampling in multiple dimensions affect our traditional aliasing constraints? How can we infill large gaps without using a model for our data? Are irregularities in sampling beneficial? Understanding land data interpolation may help to solve many problems in seismic processing.
In this paper, we address some of these issues and show some examples of multidimensional land data interpolation.
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Characteristics of Azimuthal Anisotropy in Narrow-Azimuth Marine Streamer Data
More LessTowed-streamer acquisition samples a narrow range of azimuths. We discuss the resulting sensitivity of such data to azimuthal velocity anisotropy. Correction for such effects, for example by using a residual moveout correction before migration, can significantly improve the imaging in such situations.
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Analysis of the Common-Reflection-Surface Interpolation
Authors G. Hoecht and P. RicarteThe presented interpolation method is based on the common-reflection-surface (CRS) theory. For each sample that has to be interpolated five parameters are required and estimated from the data. Therefore, the proposed method is computational more expensive than existing methods. We present the potential as well as limitations of the method. The result of a CRS interpolation strongly depends on the accuracy of the detected parameters. We analyze the behavior of the estimated parameters for different situations and investigate the effect of an adapted smoothing of the parameters. For the analysis we use the Sigsbee data set which offers numerous complex reflection and diffraction patterns. For a comparison we show the result of a f-x interpolation.
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Practical Approaches to the Common-Reflection Surface (CRS) Stack
More LessCommon-reflection surface stacking is a time-processing technique for seismic reflection data that improves signal-to-noise at the cost of along-dip resolution. The theory is based on summations across multi-dimensional pre-stack reflections, but the noise reduction benefits can be realized with a purely post-stack process. Dip and azimuth information derived from this post-stack process can yield an improved velocity analysis.
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Elimination of the Spread-Length Bias in the Common-Reflection-Surface Stack
More LessThe Common-Reflection-Surface (CRS) stack yields kinematic wavefield attributes and stacked sections based on a second-order traveltime approximation.
As the CRS stack is performed by coherence analyses this leads to attributes and traveltimes of reflection events that show a spread-length bias, i.e., the quantities obtained are subject to the search aperture.
Obviously, applications based on the attributes and traveltimes will suffer from these misfits and yield incorrect results.
In this paper a technique for the correction of the spread-length bias is presented. Based on the assumption of a linear relationship between spread-length bias and search aperture the attributes and traveltimes are extrapolated to zero aperture and thus to their correct values.
The method is related to multiple coherence analyses with different apertures. The so obtained stack and attribute sections form new pseudo pre-stack data volumes which are used for the estimation of the extrapolation operators. A synthetic data example shows that these corrections are able to significantly improve the results of subsequent applications.
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Hybrid L1/L2 Norm IRLS Method with Application to Velocity-Stack Inversion
By J. JiLeast squares (l2 norm) solutions of seismic inversion tend to be very sensitive to data points with large errors. The l1 norm minimization gives more robust solutions than l2 norm solution does. Iteratively reweighted least squares (IRLS) method which is an efficient approximate solution of the l1 norm problem is widely used for robust inversion. I propose a simple way to implement IRLS method for a hybrid l1/l2 minimization problem that behaves as l2 fit for small residual and l1 fit for large residuals. The boundary between l1 and l2 is decided by a scale factor that is applied to data before and after inversion. Synthetic and real data examples in CMP data enhancing through inversion demonstrate the improvement of the hybrid l1/l2 norm method over least-squares method when there are outliers in the data.
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Perspectives of Chemical IOR/EOR Methods in the 21th Century - A New Thermodynamic Approach
Authors I. J. Lakatos and J. Lakatos-SzabóThe role of IOR/EOR technologies at oil and gas fields is gradually increasing and they form a mainstay to preserve the existing equilibrium between production and the global demand. Thermodynamic interpretation of displacement processes is a consistent basis to classify the EOR methods and anticipate their inherent efficiency. The conclusions confirm the high potential of chemical IOR/EOR methods in the 21st century.
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