- Home
- Conferences
- Conference Proceedings
- Conferences
73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011
- Conference date: 23 May 2011 - 27 May 2011
- Location: Vienna, Austria
- ISBN: 978-90-73834-12-5
- Published: 23 May 2011
61 - 80 of 799 results
-
-
3D Seismic Multi-attribute Analysis for Fault/Fracture Delineation and Porosity Prediction – A Kuwait Case Study
Authors T. Chen, O. Khaled, G. Al-Sahlan and T. Al-RashedAn existing exploration lead in the study area is considered to be high risk due to its lack of four-way closure, whereas nearby existing producing fields all have excellent four-way closures. However, stratigraphic traps could potentially exist in this area, which would make this lead attractive for exploration. We attempt to utilize seismic attributes, not only to delineate faults and fractures as the structural fabric, but also to delineate major stratigraphic features, including mapping of porosity distribution for the zone of interest. Post-stack inversion was conducted to get layer properties and to enhance the seismic resolution. The inverted acoustic impedance was combined with conventional migrated stack for neural network analysis to predict 3D porosity volume calibrated with well data. We observed that seismic attributes are useful for fault/fracture mapping in this area. Semblance, structure cube, and dip corrected structure cube are useful for regional fault mapping; whereas curvature, spectral decomposition, and wave form classification can potentially produce very detailed maps of faults and fractures. The porosity trend of the zone of interest appears to have a similar trend compared to the fault lineaments. This could imply that porosity generation and enhancement might be structurally related.
-
-
-
Joint Interpretation Techniques with Different Azimuth Data to Depict Complex Fault Systems and Reservoirs
Authors B. Q. Zhang, Y. H. Li, T. H. Li, H. J. Zuo, Z. W. Wang and D. Y. LiThe Kongnan area is located in Huanghua depression of Bohai Bay basin in northeast China, where there are complex paleogene fault systems that dissect the area into many different types of reservoirs. It is very difficult to accurately identify the fault systems and to depict the boundaries and interior of the reservoirs with conventional seismic data and seismic interpretation techniques. In order to solve these problems high-density wide azimuth seismic data have been acquired in this area and through processing migration stack data and pre-stack migration gathers from different azimuths have been obtained. Based on these different azimuth seismic data complex fault systems have been accurately identified and reservoir boundaries have been accurately delineated by using a series of techniques including fault system optimal identification technique with different azimuth seismic data joint interpretation, reservoir characterization technique with different azimuth seismic data joint interpretation, special lithologic body recognition technique with different azimuth seismic data joint interpretation, azimuth AVO detection, and azimuth multi-attribute fracture detection. The success rate of drilling has been greatly improved by using these techniques, suggesting the feasibility and effectiveness of our methods.
-
-
-
Fracture Prediction, Actual 2010 Drilling Results, and Full Wave Forward Modeling: An Integrated Technologies Approach
Authors B. H. Link, I. Y. Kromova and N. MarmalevskyiOver the last few years Lukoil has published the results of two exhaustive studies into the problem of fracture detection. Fracture prediction methods based on reflection amplitude, reflection curvature and its derivatives, coherency cube, spectral decomposition, ant-tracking technology, azimuthal anisotropy of P-wave velocity, and DWM amplitude cube analysis. We concluded that the DWM technique was the most reliable method for fracture permeability detection (Khromova et al., 2011). Lukoil planned a 2010 drilling program for horizontal wells based on DWM technology and this paper will report on the results of that 2010 drilling program. Two horizontal wells were drilled into a limestone interval and extensive well log measurements were taken. The well results illustrate that the location of the fracture systems as predicted by DWM were accurate to within 25 metres. The DWM amplitude maps and well log results will be shown to illustrate the success of this fracture prediction technique. Also, the ability to use these actual well results, along with full wave forward modelling, and DWM technology to push the boundaries of reservoir characterization prediction using an integrated seismic-based methodology is investigated.
-
-
-
Seismic Azimuthal Anisotropy Analysis of Post-hydraulic Fracturing
Authors K. Zhang, Y. Guo and K. J. MarfurtThe Barnett Shale is one of the first and fully developed unconventional resource plays in North America. Since it has very low permeability, the Barnett Shale is now produced using multiple stages of hydraulic fracturing to provide pathways that allow hydrocarbons to reach the well bore through drilling horizontal wells perpendicular to the present-day azimuth of maximum horizontal stress. For geoscientists and engineers, the knowledge of induced fracture orientation and intensity is critical to evaluate the efficiency of the completion project and the possible need for restimulation. In this paper, we report the results of azimuthal anisotropy analysis of a shale-gas reservoir after hydraulic fracturing. In the study area, the organic-rich Barnett Shale has been extensively hydro-fractured by high pressure fluids to stimulate production prior to the acquisition of the 3D seismic survey. The objective of the seismic survey was to recognize the signature of gas- or water-charged fractured reservoir, and to identify any bypassed pay.
-
-
-
Seismic Attribute Analysis of Fractures in Woodford Shale
Authors Y. Guo and K. J. MarfurtVolumetric seismic attributes allow interpreters to map the structural deformation and subtle stratigraphic details that are not readily observable on seismic data. In this study, we investigate fracture illumination in the Woodford Shale of the Arkoma Basin, U.S.A based on seismic attribute analysis. Coherence allows us to map relatively large offset discrete faults that appear to have a wrench component, while curvature allows us to map more subtle folds and flexures that are closely associated with fracture swarms. Low acoustic impedance anomalies have a strong correlation with structural lineaments given by most-negative curvature, strongly suggesting either natural fractures or diagenetic alteration. The proximity of microseismic events to ridge/dome features suggests that the formation of ridge/dome features generated paleo-zones of structural weakness.
-
-
-
Gabor Filters for Segmentation of Salt Structures
Authors A. Solberg, A. Berthelot and L. GeliusThe suitability of Gabor filters for segmenting a salt structure present in a North Sea seismic section is investigated. A filter bank of 24 Gabor filters is designed and applied to the seismic data. Principal component analysis is applied to the resulting filter response images to extract a low number of relevant attributes. These attributes are used to train a statistical classifier to estimate the probability that each pixel is salt. The probability is then used as input to a segmentation algorithm that finds a continuous, smooth border between the salt and the surroundings. The resulting border corresponds well with a manually interpreted contour provided by an experienced interpreter.
-
-
-
Application of Time-frequency Attributes Based on Generalized S-transform for Thin Bed Indication
Authors R. D. Han, Z. H. Wan, M. S. Chen and H. Y. ZhangDuring the last decade, spectral decomposition technique has proven to be an excellent tool to describe thin beds associated with channel sands, alluvial fans, and the like. However, the traditional spectral decomposition method based on short time Fourier transform, is difficult to acquire the accurate time-frequency spectrum for non-stationary seismic signals. In addition, it generates dozens of unwieldy iso-frequency cubes, not amenable for interpretation. We propose two new time-frequency attributes based on generalized S-transform and apply them to an oilfield of western China to characterize the Triassic reservoir distribution of fluvial deposits. Compared with the traditional short time Fourier transform, the generalized S transform results in more accurate time-frequency spectrum, and generate two attributes which can directly map reservoir thickness.
-
-
-
Tackling the Stationary Zero-phase Assumption
Authors J. A. Edgar and J. I. SelvageThe assumption that the phase of seismic data is known, and is stationary with respect to time and space, is one of the few assumptions which underpin almost the entire spectrum of seismic interpretation methods. We demonstrate that the phase of 3D seismic data can be robustly estimated using an iterative kurtosis-based method. Our methodology is first applied to a noisy synthetic seismic volume and is shown to correct the non-stationary phase that is present. Results of the application of the method to a real seismic dataset indicate that non-stationary phase is present. We attempt to correct for this phase variation in 3D to leave only local apparent phase anomalies that may be attributable to geological variation. We believe that all seismic data should be subject to phase interrogation before applying techniques that require an assumption about phase to be made, and offer this method as a way to do so.
-
-
-
Interpreter Guidance for Automated Seismic Image Segmentation
Authors A. Halpert, R. G. Clapp and B. L. BiondiWhile automatic segmentation of seismic images can dramatically speed up interpretation of salt bodies and alleviate a major model-building bottleneck, human expertise at this task is valuable and should be included. Here, we demonstrate a strategy to incorporate such expertise into the highly-efficient Pairwise Region Comparison (PRC) segmentation algorithm. By supplying a limited manual interpretation of the salt boundary, interpreters can correct local inaccuracies and guide the automatic result in both 2D and 3D. In the 3D case, accuracy of the segmentation improves even in areas far from the manual picks. Examples from a wide-azimuth Gulf of Mexico survey demonstrate the effectiveness of this procedure.
-
-
-
Seismic Interpretation of Prograding Events in Tortonian Sands, Vienna Basin - Implications for Stratigraphic Modeling
Authors G. Gonzalez, M. Kornberger, T. Kuffner, E. Rieser and A. BallauriTortonian deltaic reservoir sands in the Vienna Basin contain substantial remaining HC potential. These reservoirs have been extensively drilled and produced, previous studies could not fully explain reservoir connectivity issues. The recognition of heterogeneities in reservoir modelling studies is a precondition to understanding fluid flow behaviour. This study presents the detailed mapping of prograding seismic elements using Relative Acoustic Impedance (RAI) and Spectral Decomposition (SD) attributes. These attributes facilitate the identification of geologic patterns, such as gently dipping clinoforms previously unrecognized in forced regressive stage reservoirs in this area. The morphological characteristics suggest a complex reservoir facies distribution. The patterns observed are linked to a fast and changing interplay between accommodation space and sediment supply, different feeders and/or source-shifting that are inferred to be acting over the deposition area. This intricate scenario makes ambiguous the definition of flow units based on a purely lateral well-to-well log correlation. Higher accuracy in interpretation of flow units is achieved using the aforementioned seismic attributes in addition to traditional stratigraphic modelling methods. The value added with the use of attributes certainly impacts the geological understanding during integrated multidisciplinary reservoir model workflows.
-
-
-
Visualizing Turbidite Channels Using the View Locked Color Image Grand Tour in the Chicontepec Basin, Mexico
Authors B. C. Wallet and S. Chávez-PérezThe Chicontepec Formation is a deepwater reservoir of particular strategic importance to Mexico. Despite a large volume of proven reservoirs, development has been hampered by low permeability and uncertainty about controls upon production. In order to better understand the system and how geology may impact production, we have been doing detailed interpretation of a 3D seismic survey from the northern portion o f the Chicontepec Basin. Our analysis has revealed a complex system of channels and submarine fans that have proven difficult to interpret and map. In order to aid in the interpretation of channels, we applied the View Locked Color Image Grand Tour (VLCIGT) that we had previously developed. This technique is an interactive visualization technique used to combine a large number of attributes into a single, color image. In this abstract, we show the results of the application and demonstrate its utility in visualizing the complex channel structure that is frequently found in turbidite reservoirs.
-
-
-
Stratal Domain Transformation - A Workflow
Authors G. A. D. Dorn and K. L. S. SherlockThis paper discusses the merits of 3D Stratal Domain Transformation that fully removes the 3D structural effects on a seismic volume and produces a Stratal Volume in which every horizontal slice represents a paleodepositional surface or genetic depositional unit. Up to now it has been generally accepted that any method to produce stratal slices would be difficult if not impossible to perform in 3D in areas of structural complexity. The workflow and transform described in this paper properly handles not only differential sedimentation, differential compaction, unconformities (including angular unconformities), salt bodies, canyons, carbonate platforms, but also 3D fault displacements. The resulting stratal volume can be used for interpreting all the depositional systems in the volume. The boundaries of the deposition can be captured 3 dimensionally using a Surface Wrapping method that allows multi-z mapping. The 3D meshes that represent these geobodies can then be inverse-transformed and merged with the structural interpretation. Not only does this method help unravel the stratigraphic and deformational history of any structure, it also provides a critical integrity check of the structural interpretation on which it is based.
-
-
-
Investigation of Fluid Migration Pathways Using Volumetric Seismic Damage Zone Analysis
By G. PatonDetailed analysis of the geometry of damage zones and seismic properties in the immediate vicinity of faults is required to aid interpretation of fluid migration pathways. This level of analysis can be greatly facilitated by combining manually guided fault slicing with 3D seismic attribute driven Fault Damage Zone geobody delineation to generate fault based attributes, Allan diagrams and throw maps that accurately reflect the underlying data. A critical input to such a Fault Analysis workflow is the fault surfaces. To create simple models, fault surfaces are often created by linking small scale faults as a single fault surface leading to greatly simplified representations of the true fault geometries resulting in important fluid migration pathways being overlooked. A Fault Analysis workflow that avoids the issues of over simplification and allows more complete interrogation of the underlying data is presented by showing the results of applying the workflow to a highly faulted dataset from the Norwegian North Sea.
-
-
-
Recovering Frequency-magnitude Statistics from Detection Limited Microseismic
More LessMicroseismic events are generally considered to follow a Gutenberg-Richter frequency-magnitude distribution. Previous interpretations have followed the practice in earthquake catalogue analysis of determining a Magnitude of Completeness, a magnitude above which all events appear to have been detected. In hydraulic fracture monitoring (HFM) we typically encounter single well observations; in this case, however, the Magnitude of Completeness approach can remove the majority of recorded events. We would like to provide a statistically robust estimation of the Gutenberg-Richter b-value from detection limited data, which includes as many microseismic events as possible in the calculation. Rather than defining a Magnitude of Completeness, the present method accounts for the detection limit in the calculation allowing detection-limited data to be included in the estimation. An analytical detection limit curve is introduced, based on simplifying assumptions; and it is shown that this detection limit estimation and appropriate statistical tests (the Kolmogorov-Smirnov test) can be coupled with the maximum likelihood estimate (known as the Aki estimate) of the Gutenberg-Richter b-value to provide a robust algorithm for determining a b-value across the maximum number of events.
-
-
-
Linear Bi-wing Fracture Trends Do Not Indicate Induced Hydraulic Fractures – The Rock Mechanics of Source Mechanisms
Authors S. C. Williams-Stroud, W. B. Barker and K. L. Smith Inc.Microseismic activity was monitored during stimulation of a horizontal well in a tight gas shale using a wide-aperture array of geophones deployed on the surface above the well location. The lateral was drilled perpendicular to the presumed maximum horizontal stress direction, but long, linear, well-constrained microseismic event trends developed at an angle to the wellbore. Source mechanisms of the events show the failure planes of the events were parallel to the microseismicity trends. However, in-situ stress analysis from a crossed-dipole shear log acquired in the well showed the event trends are not parallel to the maximum horizontal stress direction. This result has important implications for stress interpreted from source mechanism analysis and for the impact of natural fractures on the stimulation treatment. Prior knowledge of existing fractures in the reservoir may be critically important for deciding the deviation of horizontal wellbores in order to optimize the stimulation treatment and placement of subsequent wells for field development.
-
-
-
Elastic Full Waveform Inversion for Locations and Moment Tensors of Microseismic Events
Authors A. B. Droujinine, S. Oates and J. ItaAn Elastic Full Waveform Inversion method for estimating locations and moment tensors of microseismic events is presented and applied to a 4C multi-well data set of production induced microseismic activity from an existing field (Middle East). The algorithm minimizes differences between observed and synthetic elastic (P+S) vector waveforms in order to determine event coordinates and fault angles. It is shown to provide more accurate solutions when compared to conventional ray-based algorithms. The improved link to geomechanical modeling is seen as key to the future realization of reservoir management value from the microseismic technology.
-
-
-
Localization of Seismic Events in 3D Media by Diffraction Stacking
Authors O. Zhebel, D. Gajewski and C. VanelleThe localization of seismic events is of great importance in exploration geophysics for monitoring of for instance hydraulic fracturing. It can be successfully implemented by diffraction stacking, where the source location is obtained from the maximum of the image function. Since the maximum of the image function is distinct, even in the presence of noise very weak events can be detected. Previous research showed that the method works reliably for homogeneous 2D media. In this paper we demonstrate the extension to 3D and present numerical examples in both homogeneous and heterogeneous media. Strongly heterogeneous media are intensely affected by triplications. We show that the localization of events in such media is nevertheless possible if the most energetic arrivals are taken into account. Moreover, by using geometrical spreading as weighting factors for the input data, separation of propagation and source effects is achieved. We have studied the source effects of radiation patterns. Finally, the method was tested on field data from Southern California. Both numerical and field data application confirm the potential of the method. Conventional source location methods by event picking locate the event with a maximum spatial deviation of 1 km when compared to the location method presented here.
-
-
-
Automatic Microseism Location by Full-waveform Triangulation
More LessWe present a method for locating microseism hypocenters in both space and time, by correlating multiple reconstructed wavefields corresponding to different groups of receivers. The method is mathematically and conceptually similar to triangulation, but does not require arrival picking. The fundamental idea is that for correct velocity for the wavefield from all receivers arrives at the spatio-temporal location for the microseism simultaneously but on distinctly different paths. Thus, the wavefields for subsets of receivers do not coincide in space and time until the wavefields are at the hypocenter location. To capture the coincidence of the wavefields, we propose a new imaging condition for passive seismic datasets that is similar to the zero-lag cross correlation imaging condition but uses the cross-correlation of multiple receiver wavefields instead of the source and receiver wavefields. We demonstrate this idea on a synthetic microseismic dataset by reconstructing the wavefield using time-reversed propagation for a few groups of receivers that have distinctly different angular aperture and then applying the proposed imaging condition. This method is able to correctly image the microseisms in space and time, even though the signal-to-noise ratio is low.
-
-
-
Building Effective Anisotropic Models from Microseismic Data Acquired in a Shale-gas Reservoir
Authors I. Das, P. Singh and V. GrechkaVelocity models for locating microseismic events recorded in the oil-industry applications are usually derived from sonic logs and perforation shots. Instead of fixing these models, as is conventionally done, we update them when locating the events. This added flexibility not only improves the accuracy of predicting traveltimes of the recorded P- and S-waves but also provides a convincing evidence for anisotropy of the examined gas-bearing shale formation. While we find that velocity heterogeneity does not need to be introduced to explain the data acquired at each stage of hydraulic fracturing, the obtained models suggest time-lapse changes in the anisotropy parameters characterizing the stimulated reservoir volume.
-
-
-
Interaction of Neighboring Stages in the Set of Hydraulically Stimulated Horizontal Wells: Are the Stages too Close?
Authors A. M. Baig, T. I. Urbancic and A. GuestMicroseismic moment tensors are determined from a number of stages in a multiwell hydraulic fracutre treatment. These moment tensors are point measures of the strain in the reservoir and can be related to volumetric opening and closure of cracks. The data for these stages locate asymmetrically with respect to the treatment well in a region of the reservoir that was recently fractured. The strain from these data show volumetric increase and decrease indicating that this pre-existing fracutre network opened and closed as the treatment progressed. The dominance of closure for the later set of events implies that the stages were too proximal as previously stimulated regions were closed reducing the enhancement in permeability in these regions.
-