1,720,976 research outputs found
Time-lapse rock physics inversion of thermal heavy oil production
No full textTime-lapse (4D) seismic monitoring of thermal heavy oil production represents a simple, robust and cost-effective method of characterizing changes in reservoir conditions. Conventional 4D seismic monitoring techniques track changes in a reservoir by comparing differences in seismic amplitudes and traveltimes over calendar time. These amplitude differences offer insight into the spatial extent of production and injection effects, but the physical cause of the observed amplitude differences is ambiguous. In order to properly distinguish between the effects of heated oil, steam, pressure, and temperature more information must be extracted from the seismic data. In this study, I combine AVO analysis and rock physics modeling in a rock physics inversion to quantify petrophysical changes in the reservoir thereby offering a more complete description of subsurface conditions during SAGD operations. With the resulting estimates for change in steam and heated oil saturations, the differentiation between varied fluid responses is possible. The heterogeneity of the SAGD operation is clearly observed. Areas surrounding the western well pairs with little to no steam or heated oil present contrast significantly with the large changes observed along the well pairs to the east. This leads to opportunities for improved production efficiency through the identification of zones with significant steam baffles and barriers, which significantly increase steam and energy requirement and prioritizing production of more efficient zones. Heated oil maps can also aid in identifying the most efficient zones and help track the mobilized bitumen to ensure it is not escaping or situated beyond the reach of the production wells. Together, results of this kind give operators valuable feedback that helps reduce both costs and environmental footprint for SAGD operations
Processing of DAS and geophone VSP data from the CaMI Field Research Station
No full textThe monitoring program of CO2 injection at the Field Research Station in Newell County Alberta includes diverse surveys and new technologies. The acquisition and processing of Vertical Seismic Profiles (VSP) were undertaken for this thesis. More specifically, the analysis of three different surveys: a walk around VSP for azimuthal anisotropy analysis, zero offset VSPs to test the emerging DAS technology and walk-away VSP to obtain imaging results for straight and helical wounded fibre optic cables. From the azimuthal analysis, the fast direction was identified to the northeast with an epsilon value (0.02) indicative of weak anisotropy. For the DAS VSP processing, a calibration step was necessary to register the precise depth of DAS traces; two approaches were completed and yielded similar results. Additionally, DAS strain rate measurements were converted to strain to compare it with geophone data. The excellent correlation between the 3D seismic lines and VSP-CDP stacks and the imaging results shows that DAS is a promising technology for subsurface imaging and monitoring
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Theoretical Framework for Seismic Time-lapse Difference AVO Analysis with Validation on Physical Modelling and Field Data
No full textPerturbation theory has been widely used in many applications in seismology, more recently for time-lapse problems. We have formulated a scheme for modeling linear and nonlinear elastic time-lapse difference amplitude variation with offset data. We have expressed this framework as an expansion in orders of the baseline interface properties and time-lapse changes from the time of the baseline survey to the time of the monitor survey. We have examined our formulation with the numerical data used in literature for real time-lapse data. The results indicated to the first order that our framework is in agreement with Landrø’s linear approximation. The higher order terms represented corrections appropriate for large P- and S-wave velocities and density contrasts in the reservoir from the time of the baseline survey to the time of the monitor survey.
A physical modeling data set was acquired simulating a time-lapse problem to validate our theoretical results. Plexiglas, polyvinyl chloride (PVC), and phenolic slabs were used as proxy materials to simulate the cap rock and reservoir at the time of the baseline and monitor surveys, respectively. Reflected amplitudes were picked and corrected for geometric spreading, emergence angle, free surface, transmission loss, and radiation patterns. Our results indicated that higher order expansion terms, involving products of elastic time-lapse perturbation and baseline medium perturbation, matched laboratory data with significantly reduced error in comparison with linearized forms. We have concluded that in many plausible time-lapse scenarios, the increase in accuracy associated with higher order corrections that we observed enhanced the time-lapse modeling.
In conjunction with Talisman Energy Inc. part of Repsol Group, a multicomponent time-lapse seismic data set, which was acquired during hydraulic fracturing of two horizontal wells in the unconventional Montney Reservoir at Pouce Coupe Field in the Peace River area, has been used to validate derived linear and nonlinear theoretical results for the time-lapse AVO. The results show that the nonlinear components of the difference data interpretation scheme do not contribute significantly to estimate time-lapse AVO difference. This is consistent with the fact that the Pouce Coupe data set has a low baseline contrast and a low time-lapse contrast
A Multicomponent Walkaway Vertical Seismic Profile Experiment in a Heavy Oil Reservoir
No full textA multicomponent walkaway VSP experiment was successfully processed and used to predict rock properties in a heavy oil reservoir. Post-stack image and pre-stack gathers were made for inversion and AVO analysis. A common shot reflectivity gather was also created for AVO study at the VSP well location. P and S-wave impedance, reflectivity, Vp/Vs and density were studied. AVO attributes and their crossplots were analyzed. Furthermore, AVO Lambda-mu-rho analysis and AVO modeling were conducted. The analyses helped to identify different lithologies and changes of fluids in the target reservoir. The study showed no obvious gas effects in the target interval, a finding validated by production data. The converted-wave data had good resolution. PP-PS joint inversion added more details to P-wave inversion only. This case study demonstrated that multicomponent VSP is an effective tool to predict rock properties, characterize the reservoir, and monitor production
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Anelastic attenuation and anisotropy in seismic data: modeling and imaging
No full textAnisotropy and attenuation are critical to the modeling and analysis of seismic amplitude, phase, and traveltime data. Neglect of either of these phenomena, which are often both operating simultaneously, diminishes the resolution and interpretability of migrated images. In order to obtain an accurate image of subsurface earth, it is necessary to include both anisotropy and attenuation in inversion procedures as subsurface materials are far from being isotropic or elastic. In this thesis, I address attenuation and anisotropy problems such as modeling of wave propagation and compensating for attenuation effects in seismic images. To develop such analysis, I derive a time domain viscoacoustic constant-Q wave equation in isotropic and anisotropic media using an un-split field PML's scheme that is practically efficient and accurately simulates the constant-Q attenuation behavior and developing an Q-compensated reverse-time migration approach to compensate for attenuation effects in seismic images during migration. First, I investigate the accuracy of the new approach of viscoacoustic wave equation based on constant-Q theory. Most importantly, this approach separates attenuation and dispersion operators that allow us to mitigate both amplitude attenuation and phase dispersion effects in seismic imaging. This equation is the key modeling engine for seismic migration. Second, I present a method to improve image resolution by mitigating attenuation effects. I develop a Q-compensated reverse-time migration imaging approach (Q-RTM) and demonstrate this approach using different synthetic models. In Q-RTM, amplitude compensation happens within the migration process through manipulation of attenuation and phase dispersion terms in the time domain differential equations. Particularly, the back-propagation operator is constructed by reversing the sign only of the amplitude loss operators, but not the dispersion-related operators, a step made possible by reformulating the absorptive equations such that the two appear separately. Numerical results further verify that this Q-RTM approach can effectively improve the resolution of seismic images, particularly beneath high-attenuation zones. Finally, I extend the viscoacoustic wave equations from isotropic media to transversely isotropic (TI) media. For imaging application, I discuss the stability condition and the artifacts of shear wave triplications. The results indicate that the stable anisotropic reverse time migration is accessible by taking off anisotropy around the selected high gradient points of tilt angle in areas of rapid changes in the symmetry axes
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Double-Difference Seismic Event Relocation: A Study of the Applications and Limitations of the Relocation Problem
No full textEarthquake relocation provides refined earthquake catalogs based on additional considerations or data beyond the initial earthquake location estimates. Double-difference relocation, in particular, utilizes the assumption that ray paths in close proximity to one another will pass through a similar earth velocity structure. The method minimizes the residual difference for pairs of these travel time observations to refine event locations. This thesis focuses on the application of three double-difference methods based on differing geometries of data pairing: event-pair relocation, station-pair relocation, and double-pair relocation. In this thesis, I introduce a previously unavailable software, relocDD-py, that implements all three of these relocation methods along with a complete workflow, including data preparation, automated variable selection, and post-relocation uncertainty analysis. This software is developed in Python using many widely implemented Python packages to allow for integration into existing seismic workflows. In addition, I present studies that apply this software and methodology at various scales, including (1) a large-scale tectonic study of complex plate subduction and the resulting seismicity in Alaska and Yukon where we find direct evidence of the Totschunda-Fairweather Connector fault; (2) a regionally observed induced seismicity event with analysis of the entire earthquake sequence from Peace River, Alberta where we find activation of multiple sub-parallel faults; and finally (3) a densely monitored induced seismicity experiment which ruptured a complex network of pre-existing faults near Fox Creek, Alberta where we find limits on the depth of seismicity to the hydraulic fracturing depth. Double-difference relocation can improve existing catalogs even in sparsely monitored areas and can reduce relative location uncertainty to such a degree that detailed three-dimensional interpretation of fault structures is possible. In many cases, event-pair relocation, the most widely applied double-difference method, is sufficient to improve relative uncertainties and maintain absolute location uncertainties. However, in cases with complex velocity models and dense monitoring, the double-pair method can improve relative uncertainties beyond event-pair relocation, which may identify additional seismicity features. The double-pair method is more computationally expensive and, therefore, is not necessary in all cases. All three double-difference relocation methods have an important role to play in earthquake and other seismic event relocation and catalog refinement. My work provides a software tool and a standardized workflow for the implementation of double-difference relocation in seismic studies
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