Stress and strain from reflection seismic data

Autor: van Gent, Heijnderik Willem
Přispěvatelé: Urai, János
Jazyk: angličtina
Rok vydání: 2010
Předmět:
Zdroj: Aachen : Publikationsserver der RWTH Aachen University 196 S. : Ill., graph. Darst. (2010). = Aachen, Techn. Hochsch., Diss., 2009
Popis: The pre-drilling prediction of (paleo)-stress helps defining fracture and fault patterns which can either help or hinder hydrocarbon production, and helps to decipher the tectonic history of the crust. At the moment, paleostress studies are mostly based on the detailed mapping of faults and movement directions in the field. This limits the applicability of this approach to areas where the rocks of interest are outcropping and excludes sedimentary basins. In this work, a method is developed and tested to determine the paleostress stratigraphy solely based on 3D reflection data, and the initial work for a similar approach for ductile evaporites is presented. For the determination of paleostress, knowledge of the orientation and slip direction of the individual faults in the set is required. Both in field and seismic surveys it is relatively easy to determine the fault orientation. Determining the slip direction however remains a challenge in seismic data. In field studies, measurement of the slickenside orientation provides a quick and easy slip direction determination, but these structures are too small to be resolved in seismic data. Due to the converging pattern of slip lines, the measured slickenline does not need to represent the tectonic movement direction. Furthermore, since faults generally rupture in a number of seismic events distributed over the fault plane, contradicting slip directions formed during the same tectonic phase can overprint each other, complicating the interpretation of field based slip determination. The easiest way to determine the slip direction on faults is by connecting two points that were on direct opposite sides of the fault, prior to deformation. Unfortunately, no faulted channels or lineaments were present in the data set. By careful mapping of the Allan lines however, the slip directions of a number of faults, over a number of time periods were constrained. This data allowed for the determination of the paleostress stratigraphy of the NW corner of the Groningen High in the Netherlands, spanning from the Triassic to present-day. The paleostress states correspond well with published paleostress data. The roughness of fault planes is however not limited to the scale of slickensides. Also larger undulations are present on the fault surfaces. Recent publications, based on LiDAR measurements of outcropping faults suggest that these undulations are in the direction of fault slip. Detailed interpretation of several faults in the relatively brittle Upper Cretaceous Chalk from the same area showed that in reflection seismic, undulations are present in interpretations in different directions. It is also shown that these undulations are unlikely to be the result of aliasing, or interpolation effects. The determination of the orientation and slip direction of over 200 faults allowed the determination of the Upper Cretaceous paleostress. This result corresponds well to the paleostress results with the geometrically determined slip direction, and published results. The Late Permian Zechstein deposits of Europe consist for a large part of (ductile) evaporites. This interval decouples sub- and supra-salt deformation. The ductile deformation of these deposits does not allow the determination of the paleostress evolution using the above discussed method. However, an enclosed brittle layer, fully encased in the ductile salts, allows the visualization of the extremely complex deformation patterns, and can serve as a strain marker in these deposits. Structures observed, include various types of disharmonic folds, superimposed on the harmonic folding, which follows the top of the salt, ductile rupture (boudins) and zones of early diagentic/sedimentary thickness increase. The latter seem to affect younger deformation. These zones seem to influence the location of salt structures, showing that early structures can affect the salt tectonics and deformation of supra-salt deposits.
Databáze: OpenAIRE
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