Dissertations / Theses on the topic 'Vertical seismic profiles'

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001.
Includes bibliographical references (p. 147-152).
This thesis presents imaging results from a 3D reverse vertical seismic profile (RVSP) dataset measured at a hydrocarbon bearing pinnacle reef in northern Michigan. The study presented many challenges in seismic data processing and imaging, as the survey geometry was unique in several ways. Reverse VSP, which uses seismic sources in a borehole and receivers on the earth's surface, is fairly rare. RVSP in 3D with a random distribution of surface geophones is unprecedented. At the time this data was collected, no commercially available processing tools existed to address this geometry, so a processing scheme had to be developed. The data processing sequence presented in this thesis, which includes amplitude corrections, first break picking, deconvolution, wavefield separation, and application of statics, takes advantage of the repeatible signature of the new downhole source (Paulsson et al., 1998). Since the data can be handled in common-receiver gathers instead of the usual common-source gathers, it can be treated like several single offset VSPs during the processing sequence. Issues related to the 3D geometry and the random distribution of the receiver array need not be addressed until the imaging step. The generalized Radon transform (GRT) migration method of Miller et al. (1987) provides a high resolution image of a portion of the target reef at 4600 feet (1400 meters) depth. The high resolution of the image is largely due to the downhole source, which generated a high powered signal at frequencies up to several hundred Hertz. Another factor in the high resolution of the image is the success of receiver consistent model-based Wiener deconvolution (Haldorsen et al., 1994), possible because the source signature was repeatable. Due to adverse conditions and power system failure, a large portion of the surface array did not record data.
(cont.) The reduced spatial coverage limits the extent of the migrated image, precluding an evaluation of the effectiveness of the random receiver spread. The limited nature of the receiver array also caused artifacts resembling migration smiles in the image. These artifacts are partially suppressed by limiting the aperture of the migration, but this also removes dipping reflectors from the image. To maximize the imaging capibilities of the data, a second approach complimenting the GRT method is developed. This approach, termed vector image isochron (VII) migration, removes array artifacts from the image without losing energy from dipping reflectors. This allows artifacts in the conventional image to be identified, aiding interpretation of the GRT images. VII images also show more even illumination than conventional images, although an effect similar to NMO stretching reduces the resolution of the VII image as compared to the GRT image. The VII scheme is an extension of the GRT migration process of Miller et al. (1987), but involves forming an image which depends on the imaged plane orientation, transforming the image based on the array geometry, then finishing the GRT summation over plane orientations. The VII imaging method is derived in both 2D and 3D with the assumption that the ray paths are straight and that at least one of the arrays, source or receiver, is horizontally oriented. The surface array can have any distribution, regular or random. The other array can have any orientation in general, although this thesis assumes that it will be either another surface array or a vertically oriented borehole array. ...
by Mary L. Krasovec.
Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1985.
Microfiche copy available in Archives and Science.
Bibliography: p. 125-126.
by Carl B. Godkin.
M.S.

The integrated processing and interpretation of VSP data are developed to work together in order to enhance the final VSP interpretation. Furthermore, the interpretive processing of the VSP data within the case histories are reviewed along with the incorporation of the final VSP results (both near and far offset data) into the integrated geological/geophysical interpretations presented in the case studies. This thesis has attempted to personify the term "interpreter/processor" as first highlighted in Hardage (1985). The case histories pertain to oil and gas exploration in carbonate reef and sandstones in the Western Canadian Sedimentary Basin (WCSB). The Lanaway case history (Hinds et al., 1994a) pertains to the exploration of the Lanaway/Garrington oil field located in central Alberta, Canada. The surface seismic interpretation over the reef crest differed dramatically from the isopach of the reef-encasing shales derived from the geological logs of a borehole drilled into the reef crest. To understand the discrepancy, a VSP survey was performed and the data were interpretatively processed. The results were integrated with the known geology of the field area to uncover possible reasons for the surface seismic anomaly. field in central Alberta, Canada, using the far offset VSP survey. Existing surface seismic was used to infer that a well drilled into the interpreted North-east corner of the Ricinus reef would be successful in penetrating oil bearing carbonate reef. The well was drilled; however, the well missed the reef and a near and far offset VSP survey was used to seismically image possible reef buildups in an area around the well. The Fort St. John Graben case history (Hinds et al., 1991a; Hinds et al., 1993a) highlights exploration of a gas-filled channel sandstone using near and far offset (lateral) VSP surveys. An exploration well was drilled within the study area which intersected the target zone sandstone (the basal Kiskatinaw of the Upper Carboniferous). The target sandstone had a high shale content and was not reservoir quality. A near offset and two far offset VSP surveys were run in the exploration well to image out to a distance of 350 m to the North¬west and to the East of the well. The VSP, surface seismic and geology results (from the geological logs of the exploration and surrounding wells) are integrated to infer a clearer picture of the sand/shale relationships of the basal Kiskatinaw and detailed faulting of• the Carboniferous strata around the well and within the surface seismic line area. The Simonette field case history (Hinds et al., 1991 b; Hinds et al., 1993b) involves using VSP results to image the slope of a low-relief carbonate reef. The low-relief reef examined using the VSP data is located at the extreme end of a North-east reef spur of the Simonette Reef located in North-west Alberta, Canada. An exploration well drilled in the low-relief reef penetrated the edge of the reef. The VSP surveys were run in order to infer details of the reef slope. The interpretation of the VSP data was integrated with all other exploration data to infer the location of the crest of the low-relief reef and to assist in determining whether to whipstock the exploration well or not.
Thesis (DSc)--University of Pretoria, 2010.
Geology
unrestricted

This thesis considers anisotropy of seismic wave propagation at two oil fields in the North Caucasus region of Russia. In both oil fields, the reservoir zone displays a strong lateral variation in productivity which is thought to be caused by variations in fracture intensity. Such fractures may cause azimuthal anisotropy which can be detected in Vertical Seismic Profiles (VSPs) and Walkaway VSPs. The main aim of the thesis is to characterise this azimuthal anisotropy at three of the oil wells in these fields and to compare this anisotropy with productivity. At each of the three wells, I determine azimuthal anisotropy from VSPs by the application of techniques for estimating shear-wave splitting. I find that the polarisation direction of the fast shear-wave at all three wells is aligned approximately NNE-SSW. At two of the wells, forward modelling shows that the shear-wave splitting parameters in the top 1km can be closely matched by a model containing aligned, vertical fractures, striking NNE-SSW, in approximately the top 1 km. I am unable to resolve the anisotropy of the reservoir zone at these two wells. At the third well, strong azimuthal anisotropy of the reservoir zone is indicated by a large decrease of time delay between shear-waves propagating along vertical raypaths. This decrease is interpreted as an orthogonal rotation of the fast shear-wave polarisation direction at a depth just above the reservoir zone. Using forward modelling, I successfully match these observations with three different fractured reservoir models: the first model contains vertical fractures striking orthogonal to the presumed maximum horizontal stress direction; the second model has dipping fractures striking parallel to the maximum horizontal stress direction; and the third model has a distribution of fractures with a high internal pore-fluid pressure. Consideration of only vertical raypaths through the reservoir cannot discriminate between these models. However, modelling of non-vertical propagation from far-offset VSPs suggests that the dipping fracture model is the better model, although the lack of observations above the reservoir at this well means that other interpretations cannot be excluded.

Le filtrage matriciel, obtenu par projection sur le premier vecteur propre de la matrice spectrale, constitue un outil performant pour l'etude de profils sismiques. C'est un traitement multidimensionnel assez simple a mettre en uvre et qui, par amelioration du rapport signal sur bruit, permet de mettre en evidence les arrivees d'energie caracterisant les structures geologiques. La methode necessite peu d'hypotheses a priori; elle est basee sur les relations frequentielles entre signaux dont la fonction de transfert est definie par le premier vecteur propre de la matrice. L'application a differents profils ecors et leur interpretation structurale permettent de cerner les performances et les limites de la methode: le traitement de profils de reflexion grand angle (campagne preliminaire ecors alpes 85) est peu efficace a cause du caractere tres bruite des donnees; par contre, le traitement de sections de type grands profils donne de bons resultats (profils de reflexion verticale et de reflexion grand angle ecors alpes 86, profil de refraction ecors nord de la france)

Cette these presente plusieurs sujets ayant trait au trace de rais, utilise soit directement pour obtenir des positions d'interfaces et des lenteurs de couches, soit indirectement pour obtenir des temps de parcours et des termes d'amplitude pour la migration. Le premier sujet traite deux ameliorations d'une methode existante, qui utilise la methode des moindres carres pour l'inversion d'un modele a deux dimensions, a partir des temps de parcours des ondes montantes et descendantes. Le modele est constitue de couches a vitesse constante, separees par des interfaces definis par des courbes. Le second sujet traite de l'obtention de modeles uni-dimensionnels et de statique de sources a partir des temps de parcours des ondes descendantes de vsp a offset, et de l'utilisation de ces modeles dans un algorithme de migration calculant des rais refractes dans ces modeles. Le troisieme sujet traite de l'inversion simultanee des temps de parcours et des angles d'arrivee aux recepteurs, piques sur des donnees vsp a trois composantes. Deux methodes sont presentees. Elles utilisent toutes deux la methode des moindres carres, mais different radicalement par le choix de la fonction de cout, ainsi que par le type de trace de rais utilise.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN.
Includes bibliographies.
by Timothy H. Keho.
Ph.D.

L'analyse des donnees stratigraphiques et structurales de la serrania del interior confirme l'existence de 2 cycles sedimentaires cretace moyen-miocene. L'interpretation des profils sismique montre que la partie enfouie de l'edifice est structuree par des accidents suggerant la presence d'un decollement. L'interpretation gravimetrique et aeromagnetique confirme que la serrania est un exemple de chaine d'avant pays decollee et mise en place dans un contexte particulier associant une composante principale en coulissage dextre avec une collision oblique

In this thesis I address the problem of determining fracture properties of subsurface rocks from geophysical surface seismic and vertical seismic profile (VSP) data. In the first part of this thesis I perform multi-attribute analysis, including frequency content, amplitude, travel time and angle of rotation studies on field VSP data from two different carbonate fields, both containing time-lapse surveys. I compare the findings to independent data available in the region and find that the interpreted fracture orientations from the attribute analyses correlate with independent fracture studies in the area, the principal axis of major faults, or the maximum horizontal stress of the area studied. Although I show the existence of these correlations, due to the limited knowledge of the rock properties, these correlations are only qualitative. A more robust inversion of fracture properties requires more knowledge of the physical properties of the medium and forward modelling of the seismic response. A rock physics theory would be required to model the elastic response of the fractured rock; hence a more quantitative fracture characterisation is necessary. In the second part of this thesis I address this need by developing and testing a method for fracture density inversion. Linearised approximations are commonly used in azimuthal amplitude versus offset (AVO) analysis. However, these approximations perform poorly at large angles of incidence where the effect of fractures is more significant. The method proposed here uses a model based approach that does not use these approximations but calculates the exact azimuthal AVO response based on prior knowledge of the elastic constants of the medium, assumed to be known, and a range of fracture densities. A rock physics theory is used for modelling the elastic constants of the fractured rock. I then create a linearized relationship for a specific model that separates the effect due to fracture density from the modelled AVOZ responses. This separation is key to the method, as it provides both a new set of orthogonal basis functions that can be used to express the AVOZ response of field data, and a set of coefficients that are related to fracture density. In general, the inversion is based on these coefficients. The coefficient or coefficients which present the highest correlation with fracture density must be determined on a case by case basis, as they will vary depending on the contrast between the elastic constants across the boundary of interest. I develop and test the method on synthetic surface seismic data and then apply it to seismic data acquired from a laboratory-scale physical geological model. Due to the prior knowledge of the rock properties and structure of the physical geological model, I am able to corroborate that the inverted fracture density from the seismic data matches that of the physical model within the error. I compare the inversion for two different levels of uncertainty in the velocities and densities of the modelled reflection coefficients and show that the inversion results are more precise and accurate when there is less uncertainty in the rock properties of the modelled reflection coefficients. In both the synthetic and physical geological model studies I find that the inversion is optimal for a certain range of offsets/angles of incidence. This means that the optimal range for inversion must be found on a case by case basis, as it depends on the behaviour of the data. Finally, as the inversion relies on the input modelled azimuthal AVO curves, a careful choice of the input rock properties is essential for the inversion process. The inverted fracture density values will only be valid if the rock properties of the field data fall within the range of the modelled ones. This is a limitation of the method, as adequate knowledge of the rock properties is not always available.

Multiple geophysical and geological data sets were compiled, reprocessed, and interpreted using state-of-the-art signal processing and modeling algorithms to characterize the complex post-Paleozoic geology that overlies the southwestern projection of the Fluorspar Area Fault Complex (FAFC) in western Kentucky. Specific data included 21.5 km of SH-wave seismic reflection, 1.5 km of P-wave seismic reflection, 2 km of electrical resistivity, vertical seismic profiles, Vp and Vs sonic-suspension logs, and 930 lithologic borehole logs. The resultant model indicates three general northeast–southwest-oriented fault zones pass through the study area as southwestern extensions of parts of the FAFC. These fault zones form two significant subparallel grabens with ancillary substructures. The geometry of the interpreted fault zones indicates that they have undergone episodic tectonic deformation since their first formation. Evidence of thickening and steeply dipping reflectors within Tertiary and Quaternary sediment in the downthrown blocks indicate syndepositional movement. Subtle thickening and lack of steeply dipping intraformational reflectors in the Cretaceous suggest a more quiescent period, with sediment deposition unconformably draping and filling the earlier Paleozoic structural surface. There is also evidence that the Tertiary and early Quaternary reactivation was associated with an extensional to compressional regional stress reversal, as manifested by the antiformal folds seen in the hanging wall reflectors and the potential small-amplitude force folds in the Quaternary alluvium, as well as a clear displacement inversion along the Metropolis-loess seismic horizon in two high-resolution reflection images. A surface shear-wave splitting experiment proved to be an efficient and effective tool for characterizing shallow subsurface azimuthally anisotropic geologic inclusions in low-impedance water-saturated sediment environments. The measured azimuthal anisotropy across a well-constrained N60ºE-striking fault exhibited a natural coordinate system that had a fast direction coincident with the fault strike and an orthogonal slow direction. This is also one indicator that faults inactive during significant geologic intervals (i.e., Holocene) do not "heal". Integrated shear-wave velocity models and electrical resistivity tomography profiles across the fault zones exhibit lower shear-wave velocities and resistivities within the deformation zones compared with values outside the boundaries. This is additional evidence that the deformed sediment does not reconsolidate or heal, but that the sediment particle configuration remains more loosely packed, providing an increase in the overall porosity (i.e., hydraulic conductivity). This can wholly or in large part explain the anomalous contaminant plume migration path that is coincident with the deformed zones of the regional gravel groundwater aquifer.

L’objectif de cette thèse est de mieux comprendre la structure de ce champ, connu principalement par les puits de production, grâce à la première sismique 3D récemment acquise et en intégrant les informations fournies par la sismique de puits. Étant donné l’importance des pendages, les réflexions en sismique de puits zéro offset sont attendues principalement sur les composantes horizontales. Une méthode originale d’orientation des 3 composantes est employée et les résultats confirment la présence de réflecteurs pentés. Les résultats migrés en profondeur sont plus précis dans le recouvrement mais la zone réservoir n’est pas améliorée, car les images temps ne permettent pas de mesurer les pendages et courbures résiduelles dans la zone d’intérêt en raison de forts multiples et d’un niveau de bruit important. Une nouvelle technique prototype de migration PSTM, permettant une sélection de l’azimut, du pendage géologique et la recherche automatique du meilleur pendage locale est présentée
The objective of the present PhD thesis is to improve the structural understanding of the Aghajari field using 3D seismic imaging, and well seismic. The lack of seismic response of the dipping horizons in the reservoir oil zone constitutes a major identified difficulty. Given the dip values of the reflectors in the pay zone, the P-P reflections are expected to appear mainly on the horizontal components of the VSP data, justifying the processing of the 3 components. An innovative method of 3C VSP orientation was developed. Several new approaches of seismic imaging have been applied in order to investigate and improve the reservoir illumination. The depth migrated image is improved in the overburden, but not at reservoir level,due to low signal to noise, thus poor dip and velocity determination in the reservoir interval. A new Kirchhoff PSTM prototype technique, allowing selection of azimuth sector, offset range and geological dip,with automatic optimization of the local dip is presented

Les capteurs distribués à fibre optique (aussi nommés DAS) sont une nouvelle technologie d'acquisition sismique qui utilise des câbles traditionnels à fibre optique pour fournir une mesure de la déformation le long du câble. Ce système d'acquisition est largement utilisé dans les profils sismiques verticaux (PSV). Le couplage est un facteur clé qui a une grande influence sur la qualité des données. Alors que, pour les acquisitions PSV, les géophones sont attachés à la paroi du puits, le câble de fibre optique est soit cimenté derrière le tubage, soit attaché avec des pinces rigides au tubage ou simplement descendu dans le puits. Cette dernière stratégie de déploiement donne généralement le plus petit rapport signal sur bruit, mais est considérée comme la plus rentable en particulier pour les installations dans des puits existants. Cette thèse porte sur la problématique du couplage du DAS quand le câble est simplement descendu dans le puits. Nous développons des modèles numériques pour analyser les données réelles. L'interprétation de ces résultats nous permet de conclure qu'un contact immédiat du câble avec la paroi du puits avec une force de contact calculée est nécessaire pour fournir des bonnes conditions de couplage. Sur la base de ces résultats, nous proposons des solutions pour optimiser davantage les acquisitions avec le système DAS. Nous modifions numériquement la force de contact et les propriétés élastiques du câble DAS et démontrons comment ces modifications peuvent améliorer mais aussi détériorer la qualité des données. Enfin, nous proposons un algorithme de détection du couplage qui permet d'assurer l'acquisition de données réelles avec un rapport signal / bruit élevé
Distributed Acoustic Sensing (DAS) is a new technology of seismic acquisition that relies on traditional fibre-optic cables to provide inline strain measurement. This acquisition system is largely used in vertical seismic profiling (VSP) surveys. Coupling is a key factor influencing data quality. While geophones and accelerometers are clamped to the borehole wall during VSP surveys, the fibre cable is either clamped and then cemented behind the casing, or attached with rigid clamps to the tubing, or loosely lowered into the borehole. The latter deployment strategy, also called wireline deployment, usually acquires the lowest level of signal but is regarded as the most cost-effective in particular for existing well installations. This PhD thesis addresses the problematic of coupling of DAS using wireline deployment. We develop numerical models that are used to analyse real data. The interpretation of these results allows us concluding that an immediate contact of the cable with the borehole wall with a computed contact force is required to provide good coupling conditions. Based on those findings, we propose solutions to further optimise DAS acquisitions. We numerically modify the contact force and the elastic properties of the DAS cable and show how these modifications can improve but also deteriorate data quality. Finally, we propose a coupling detection algorithm that is applied to real datasets and allows ensuring the acquisition of data with a high signal-to-noise ratio

Du fait de l’épuisement des réserves de pétrole, l’exploration et la production sont réalisées dans des environnements de plus en plus complexes. Faire de l’imagerie sismique sous le sel allochtone (par exemple dômes de sel) demeure une tâche difficile à cause du fait contraste de vitesse dentre le sel et les sédiments voisins et les structures très complexes produites par les déplacements de sel. Les nappes de sel allochtone couvrent de nombreuses régions potentiellement productives dans l’offshore profond du Golfe du Mexique. Forer la base du sel est une tâche extrêmement difficile en raison des pressions de pore fortement variables que l’on recontre dans les sédiments sous le sel. Des méthodes sismiques pour estimer la vitesse des ondes sismiques peuvent être employées en même temps que des formules empiriques pour prévoir la pression de pore. Cependant, il est souvent impossible de mesures précises depuis la surface, et nous avons donc employé des données VSP (Vertical Seismic Profile) “walk-away” cela implique d’effectuer plusieurs tirs sismique à diverses distances du forage (géneralement avec un dispositif de canons á air) tout en enregistrement les vitesses mesurees par des geophones placés à des profondeurs appropriées dans le forage. Avant cette thèse, les données étaient traitées en utilisant l’information d’amplitude en fonction de l’angle dans un simple approximation 1D ou en utilisant l’information de temps de parcours (également avec une approximation 1D). Dans cette thèse, j’ai effectué une inversion 2D de forme d’onde pour résoudre le problème d’estimation des vitesses. Cela a l’avantage d’inverser simultanément l’ensemble des données (comprenant les ondes transmises, les ondes refléchies et les ondes converties) et la méthode inclut l’information de temps de parcours et d’amplitude. L’inversion a été exécute avec des méthodes locales d’inversion du fait de la taille du problème inverse et de la difficulté du problème direct. Les problèmes liés aux grandes variations de le sensibilité inhérents à l’acquisition de données, ont conduit à un examen de la méthode de Gauss- Newton et à des matrices, de préconditionnement possibles pour la méthode du gradient conjugué. En raison de la nature mal contrainte du problème inverse, une régularisation a été appliquée avec une méthode de préconditionnement innovatrice. La méthodologie a été appliquée à des données réelles et la pression de pore a été prédite en utilisant l’équation bien établie de Eaton. En outre, les structures sous le sel ont été déterminées, confirment ainsi l’efficacité de cette technique
Depletion of the earth’s hydrocarbon reserves has led to exploration and production in increasingly complex environments. Imaging beneath allochthonous salt (e. G. Salt domes) remains a challenging task for seismic techniques due to the large velocity contrast of the salt with neighbouring sediments and the very complex structures generated by salt movement. Extensive allochthonous salt sheets cover many potentially productive regions in the deep-water Gulf of Mexico. Drilling through the base of salt is an extremely challenging task due to widely varying pore-pressure found in the sediments beneath. Seismic methods to estimate the seismic velocity can be used in conjunction with empirical formula to predict the pore pressure. However, accurate measurements are often not possible from surface reflection seismic data, so walk-away Vertical Seismic Profile (VSP) data has been used. This involves repeatedly firing a seismic source at various distances from the borehole (usually an airgun array) while recording the velocities measured by geophones in the borehole placed at appropriate depths near the base of the salt. Before this thesis, the data had been processed using the amplitude versus angle information in a simple one-dimension approximation or using travel time information (also using a 1D assumption). In this thesis, I have used 2D full waveform inversion to tackle the problem of velocity estimation. This has the advantage of simultaneously inverting the whole dataset (including transmitted waves, reflected waves, converted waves) and the method includes traveltime and amplitude information. The inversion was performed using local inversion methods due to the size of the inverse problem and the cost of the forward problem. Concerns over large sensitivity variations, that are inherent in the data acquisition, have lead to an examination of the Gauss-Newton method and possible preconditioning matrices for the conjugate gradient method. Due to the poorly constrained nature of the inverse problem, a smoothness constraint has been applied with an innovative preconditioning method. The methodology has been applied to real data and the pore pressure has been predicted using the well established Eaton equation. In addition, the sub-salt structure was recovered, further demonstrating the value of this technique

The integrated processing and interpretation of VSP data are developed to work together in order to enhance the final VSP interpretation. Furthermore, the interpretive processing of the VSP data within the case histories are reviewed along with the incorporation of the final VSP results (both near and far offset data) into the integrated geological/geophysical interpretations presented in the case studies. This thesis has attempted to personify the term "interpreter/processor" as first highlighted in Hardage (1985). The case histories pertain to oil and gas exploration in carbonate reef and sandstones in the Western Canadian Sedimentary Basin (WCSB). The Lanaway case history (Hinds et al., 1994a) pertains to the exploration of the Lanaway/Garrington oil field located in central Alberta, Canada. The surface seismic interpretation over the reef crest differed dramatically from the isopach of the reef-encasing shales derived from the geological logs of a borehole drilled into the reef crest. To understand the discrepancy, a VSP survey was performed and the data were interpretatively processed. The results were integrated with the known geology of the field area to uncover possible reasons for the surface seismic anomaly. field in central Alberta, Canada, using the far offset VSP survey. Existing surface seismic was used to infer that a well drilled into the interpreted North-east corner of the Ricinus reef would be successful in penetrating oil bearing carbonate reef. The well was drilled; however, the well missed the reef and a near and far offset VSP survey was used to seismically image possible reef buildups in an area around the well. The Fort St. John Graben case history (Hinds et al., 1991a; Hinds et al., 1993a) highlights exploration of a gas-filled channel sandstone using near and far offset (lateral) VSP surveys. An exploration well was drilled within the study area which intersected the target zone sandstone (the basal Kiskatinaw of the Upper Carboniferous). The target sandstone had a high shale content and was not reservoir quality. A near offset and two far offset VSP surveys were run in the exploration well to image out to a distance of 350 m to the North-west and to the East of the well. The VSP, surface seismic and geology results (from the geological logs of the exploration and surrounding wells) are integrated to infer a clearer picture of the sand/shale relationships of the basal Kiskatinaw and detailed faulting of the Carboniferous strata around the well and within the surface seismic line area. The Simonette field case history (Hinds et al., 1991 b; Hinds et al., 1993b) involves using VSP results to image the slope of a low-relief carbonate reef. The low-relief reef examined using the VSP data is located at the extreme end of a North-east reef spur of the Simonette Reef located in North-west Alberta, Canada. An exploration well drilled in the low-relief reef penetrated the edge of the reef. The VSP surveys were run in order to infer details of the reef slope. The interpretation of the VSP data was integrated with all other exploration data to infer the location of the crest of the low-relief reef and to assist in determining whether to whipstock the exploration well or not.
Thesis (DSc)--University of Pretoria, 2010.
Geology
unrestricted

Three-dimensional slant stacks simulate the response of an elastic medium for both an incident (ray parameter q) and a scattered (ray parameter p) plane wave and are implemented by following a slant stack of common shot gathers by a second slant stack of common ray parameter gathers. Three-dimensional localised slant stacks are developed, and applied to analyse reverse vertical seismic profiles. The application of slant stacks to borehole data differs from the surface seismic case in that the velocities measured from plane wave decomposition are horizontal and vertical phase velocities. Velocity and dip estimates for a model with iso-velocity layers and plane interfaces with any dip are obtained using the slant stacks without explicitly utilizing traveltimes. The estimation scheme is based on a layer stripping approach. The direct arrivals are used to determine the velocity and the reflections are used to determine the dip of the reflector.

Thesis (M. Sc.)--University of Alberta, 2009.
Title from pdf file main screen (viewed on July 16, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Geophysics, Department of Physics, University of Alberta." Includes bibliographical references.