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CGG
France

Curvature describes how much a line deviates from being straight or a surface from being flat. When curvature is used to interpret gravity and magnetic anomalies, we try to delineate geometric information of subsurface structures from an observed nongeometric quantity. In this work, I evaluated curvature attributes of the equipotential surface as functions of gravity gradients and analyzed the differences between the theoretical derivation and a practical application. I computed curvature of a synthetic model that consisted of representative structures (ridge, valley, basin, dome, and vertical cylinder) and curvature of the equipotential surface, gravity, and vertical gravity gradient (which is equivalent to the magnetic reduction-to-the-pole result) due to the same model. A comparison of curvature of such a geometric surface and curvature of different gravity quantities was then made to help understand these curvature differences and an indirect link between curvature of gravity data and actual structures. Finally, I applied curvature analysis to a magnetic anomaly grid in the Gaspé belt of Quebec, Canada, to illustrate its useful property of enhancing subtle features. © 2014 Society of Exploration Geophysicists. Source


One major purpose of gravity and magnetic transformations is to produce a result that can be related to geology. The terracing operator achieves this purpose by converting gravity and magnetic data into a geologic map-like field wherein homogeneous domains with sharp domain boundaries are defined. Edge-preserving smoothing filters developed in image processing have the same capability. I have applied the Kuwahara, mean of least variance, and symmetric nearest neighbor filters to gravity and magnetic data. Synthetic and field data examples suggest that these edge-preserving smoothing filters produce terraced effects cleaner than the terracing operator, and the mean of least variance filter often produces the cleanest and sharpest result. © 2016 Society of Exploration Geophysicists. Source


Seismic migration is a multichannel process, in which some of the properties depend on various grid spacings. First, there is the acquisition grid, which actually consists of two grids: a grid of source locations and, for each source location, a grid of receiver locations. In addition, there is a third grid, the migration grid, whose spacings also affect properties of the migration. Sampling theory imposes restrictions on migration, limiting the frequency content that can be migrated reliably given the grid spacings. The presence of three grids complicates the application of sampling theory except in unusual situations (e.g., the isolated migration of a single shot record). I analyzed the effects of the grids on different types of migration (Kirchhoff, wavefield extrapolation migration, and slant-stack migration), specifically in the context of migration operator antialiasing. I evaluated general antialiasing criteria for the different types of migration; my examples placed particular emphasis on one style of data acquisition, orthogonal source and receiver lines, which is commonly used on land and which presents particular challenges for the analysis. It is known that migration artifacts caused by inadequate antialiasing can interfere with velocity and amplitude analyses. I found, in addition, that even migrations with adequate antialiasing protection can have the side effect of inaccurate amplitudes resulting from a given acquisition, and I tested how this effect can be compensated. © 2013 Society of Exploration Geophysicists. Source


Rotating the gravity gradient tensor about a vertical axis by an appropriate angle allows one to express its components as functions of the curvatures of the equipotential surface. The description permits the identification of the gravity gradient tensor as the Newtonian tidal tensor and part of the tidal potential. The identification improves the understanding and interpretation of gravity gradient data. With the use of the plunge of the eigenvector associated with the largest eigenvalue or plunge of the main tidal force, it is possible to estimate the location and depth of buried gravity sources; this is developed in model data and applied to FALCON airborne gravity gradiometer data from the Canning Basin, Australia. © 2016 Society of Exploration Geophysicists. Source


Fedotov S.L.,CGG
7th EAGE Saint Petersburg International Conference and Exhibition: Understanding the Harmony of the Earth's Resources Through Integration of Geosciences | Year: 2016

Seismic data has long been successfully used in building of reservoir models. Building of a structural framework, sequence- and seismic stratigraphy interpretation as well as reservoir properties characterization in the interwell space are common seismic "specialties". In recent years, a new direction in the use of seismic data is actively developing - that is, in geomechanical model building. Geomechanical factors play an important role at all stages of the life of a field. As a result, there is a need to assess and manage them, starting with a forecast of drilling risks and ending with a maximization of production. Geomechanical models are vital in well planning in the sense of forecasting possible drilling problems. Wellbore stability, combined with the pore pressure determines restrictions on mud weight required for secure drilling. Reliable geomechanical model is ultimately needed while planning hydraulic fracturing in order to intensify production of hydrocarbons. Exploration for hydrocarbons in complex reservoirs and difficult conditions, as well as their further development requires improved and innovative approaches. In this regard, efficient use of seismic data in building of geomechanical models is very important.. Source

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