Some Improvements in Intensely Faulted Geological Setting Interpretation by a Multi-Scale Approach

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Subsurface deformed zones and their characteristics have a substantial influence on the distribution of oil and gas reserves as well as on production. The use of seismic data for delineating structural compartments and for modelling fault blocks in a region subjected to intense, multiphase tectonic events can be a very difficult and non-unique task as multiple interpretive solutions are possible. Generally, authors describe and substantiate the modelling technology workflow based on complex multiscale averaging of horizontal seismic slices. In this paper our discussion is restricted to the specific case of intense multiphase and multidirectional deformations and routinely processed seismic data. Instead of fault systems that appear to follow trends matching regional tectonic styles, the elementary fault planes interpreted from seismic data sometimes look chaotic. To increase the reliability of seismic interpretation and derive reasonable geological models, modification of an effective fault modeling technique is introduced. It employs a multiscale, integrated geologic approach along with seismic effective modelling basics, i.e. comprising initial noise and data spectrum considerations, model simplification and adjustment to the interpretive setting. An effective fault model includes effective faults – linear approximations of unambiguous fault planes as well as groups of ‘scattered’ elementary planes. Effective faults are used to delineate different zones of comparable rock breaking deformation. These are characterized by an areal distribution of fault planes seen on stratal seismic slices. An approximation is made using specially processed seismic attribute stratal slices, which could be referred to as seismic multiscale fracturing images. The processing algorithms include smoothing, smart averaging, and coherent filtration. Piecewise, discontinuous values of raw seismic fracturing after smoothing provide an additional opportunity to delineate deformed zones and also to upgrade the geological model based on production data. The Chayandinskoye Field in East Siberia was chosen to demonstrate the effective fault modelling technique on an intensely faulted geological setting.