RSS Cientifico geral Frequent errors in the geological interpretation of seismic lines

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1) All geological observation are theory laden. 2) Geoscientists forget to use the geological context on tentative geological interpretations of the seismic lines, locating them in relation to geographic or administrative basins and not to sedimentary basins defined in a specific basin classification. 3) Using the classification of Bally & Snelson (1980), geoscientists know, in advance, what they must to look for on seismic lines, because it gives the geological context of the main geological events and critical hydrocarbon parameters. 4) An easy refutation test of a geological interpretation (cross-section or seismic line) is to look at the dip of the proposed fault planes, which, at scale 1:1, must dip according to the Anderson's theory of faulting. 5) Every time a geoscientist shows you a delta slope on a seismic line, there is a high probability that he is showing a continental slope. The large majority of delta slopes are under seismic resolution. 6) A delta height, rarely, exceeds 100 m. A delta slope height, rarely, exceeds, 250 m. The length of a delta slope can reach more than 100 km. In appropriated geological settings, delta slopes are just visible on seismic lines with an important vertical exaggeration. 7) Geoscientists forget, often, that a seismic line looks like a geological cross section, but its vertical scale is in time (t.w.t.) and not in meters. A lot of corrections must be take into account. 8) The geometrical relationships between seismic reflectors and seismic surfaces defined, by reflections terminations, have a geological meaning just in its original depositional position. 9) At the scale of a sedimentary basin, all chronostratigraphic depositional surfaces have, a geometry, more or less, sigmoidal, with subhorizontal sectors confined by seaward dipping sectors. 10) In sequential stratigraphy, an unconformity is an erosional surface induced by a significant relative sea level fall. In other branches of the Geology an unconformity can have other meanings. 11) Some geoscientists continue to forget in their models the long periods of calm where nothing happens. In most stratigraphic sections, the duration of the hiatus is, generally, greater than the total duration of real deposition of the preserved sediments. 12) Few geoscientists know the difference between absolute and relative sea level. In addition, generally, they do not have any idea how sea level changes are measured, but they use them to explain the cyclicity of sedimentary deposits. 13) "When the sea level rise, we get a transgression and when the sea level falls we have a regression" [sic] is a false statement. A sedimentary transgression does not exist in Geology. A set of increasingly smaller sedimentary regressions can be, eventually, interpreted as the consequence of marine ingressions (transgressions). 14) When interpreting, in geological terms, a seismic line, do not forget, that the amount of sediments must be kept, more or less, constant. 15) Seismic lines are bad copies of geological reality. Tentative geological interpretations of seismic lines are far from showing the geological reality: they have a time vertical scale and a lot of lateral velocity changes inducing a lot of pitfalls. 16) Potential marine source-rock, can be localize, in the field or on seismic lines. They lie along the interfaces between retrogradational and progradational intervals.17) An angular unconformity is just a tectonically enhanced cryptic unconformity, i.e., an erosional surfaces induced by a relative sea level fall. Hydrocarbons traps associated with angular unconformities are independent of the mapping of the unconformity. They are defined by the maps of the reservoir-rock, sealing-rock and hydrocarbon migration paths. 18) Structural traps are developed in shortened geological structures. They have their own closure (four way dips). Traps against faults do not exist. Few geoscientists know what is a morphological trap by juxtaposition. Hydrodynamic traps in the majority of the cases are, totally, forgotten. 19) The first step in a tentative geological interpretations of a seismic line is to decide if the sediments are shortened or lengthened. A bad decision leads, necessarily, to a wrong tentative interpretation, because the geoscientist will be looking for geological events that are not present on the seismic line. 20) Lithological predictions can just be made on tentative geological interpretations of seismic lines made at the highest hierarchical level, i.e., at the sequence-paracycle level, in which the different depositional systems tracts and depositional systems are recognized.​



Info Adicional:
1) All geological observation are theory laden. 2) Geoscientists forget to use the geological context on tentative geological interpretations of the seismic lines, locating them in relation to geographic or administrative basins and not to sedimentary basins defined in a specific basin classification. 3) Using the classification of Bally & Snelson (1980), geoscientists know, in advance, what they must to look for on seismic lines, because it gives the geological context of the main geological events and critical hydrocarbon parameters. 4) An easy refutation test of a geological interpretation (cross-section or seismic line) is to look at the dip of the proposed fault planes, which, at scale 1:1, must dip according to the Anderson's theory of faulting. 5) Every time a geoscientist shows you a delta slope on a seismic line, there is a high probability that he is showing a continental slope. The large majority of delta slopes are under seismic resolution. 6) A delta height, rarely, exceeds 100 m. A delta slope height, rarely, exceeds, 250 m. The length of a delta slope can reach more than 100 km. In appropriated geological settings, delta slopes are just visible on seismic lines with an important vertical exaggeration. 7) Geoscientists forget, often, that a seismic line looks like a geological cross section, but its vertical scale is in time (t.w.t.) and not in meters. A lot of corrections must be take into account. 8) The geometrical relationships between seismic reflectors and seismic surfaces defined, by reflections terminations, have a geological meaning just in its original depositional position. 9) At the scale of a sedimentary basin, all chronostratigraphic depositional surfaces have, a geometry, more or less, sigmoidal, with subhorizontal sectors confined by seaward dipping sectors. 10) In sequential stratigraphy, an unconformity is an erosional surface induced by a significant relative sea level fall. In other branches of the Geology an unconformity can have other meanings. 11) Some geoscientists continue to forget in their models the long periods of calm where nothing happens. In most stratigraphic sections, the duration of the hiatus is, generally, greater than the total duration of real deposition of the preserved sediments. 12) Few geoscientists know the difference between absolute and relative sea level. In addition, generally, they do not have any idea how sea level changes are measured, but they use them to explain the cyclicity of sedimentary deposits. 13) "When the sea level rise, we get a transgression and when the sea level falls we have a regression" [sic] is a false statement. A sedimentary transgression does not exist in Geology. A set of increasingly smaller sedimentary regressions can be, eventually, interpreted as the consequence of marine ingressions (transgressions). 14) When interpreting, in geological terms, a seismic line, do not forget, that the amount of sediments must be kept, more or less, constant. 15) Seismic lines are bad copies of geological reality. Tentative geological interpretations of seismic lines are far from showing the geological reality: they have a time vertical scale and a lot of lateral velocity changes inducing a lot of pitfalls. 16) Potential marine source-rock, can be localize, in the field or on seismic lines. They lie along the interfaces between retrogradational and progradational intervals.17) An angular unconformity is just a tectonically enhanced cryptic unconformity, i.e., an erosional surfaces induced by a relative sea level fall. Hydrocarbons traps associated with angular unconformities are independent of the mapping of the unconformity. They are defined by the maps of the reservoir-rock, sealing-rock and hydrocarbon migration paths. 18) Structural traps are developed in shortened geological structures. They have their own closure (four way dips). Traps against faults do not exist. Few geoscientists know what is a morphological trap by juxtaposition. Hydrodynamic traps in the majority of the cases are, totally, forgotten. 19) The first step in a tentative geological interpretations of a seismic line is to decide if the sediments are shortened or lengthened. A bad decision leads, necessarily, to a wrong tentative interpretation, because the geoscientist will be looking for geological events that are not present on the seismic line. 20) Lithological predictions can just be made on tentative geological interpretations of seismic lines made at the highest hierarchical level, i.e., at the sequence-paracycle level, in which the different depositional systems tracts and depositional systems are recognized.



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