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Integrated interpretation of seismic and magnetotelluric data on Shurab diapirs in Qom basin, Central Iran

Oskooi B., Moradi M., Smirnov M.

Acta Geophysica

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2019

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Vol. 67, no. 4

1071--1090

EN

In recent decades, diapirs are frequently used for CO2 and natural gas storage due to their extremely impermeable and nonreactive characteristics. Among various approaches, we use an integrated interpretation approach to resolve the diapir no. 4 belonging to the Shurab diapirs (SD). The SD is a group of diapirs that have pierced to the surface of the Qom basin of Central Iran, which is a candidate for natural gas storages. The complex geology of the SD is the main cause that previous 2D seismic surveys across the diapir could not provide required information to propose any location for any exploration borehole. Consequentially, 28 magnetotelluric (MT) and 1 audio-magnetotelluric station were measured along a SW-NE profle. Dimensionality and strike analysis for all stations is done by the use of phase tensor analysis. We used the nonlinear conjugate gradient algorithm to invert the TE- and TM-modes data simultaneously in 2D. The resistivity model was compared with the interpreted results of the post-stack depth migration model using seismic attributes. In order to extract the determinative geological information from the low-quality seismic section, envelope, variance, sweetness and instantaneous frequencies attributes were used. The integrated interpretation of the seismic and MT data resolves a precise geometry of the salt body, location of the dense part of the diapir as well as the tectonics around the diapir. The integrated interpretation of seismic and MT data of diapir no. 4 resulted in an exploration drilling program.

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Interpretacja zasięgu eksternidów waryscyjskich na eksperymentalnym profilu sejsmicznym GRUNDY 2003

Śliwiński Z., Antonowicz J., Iwanowska E., Malinowski M., Grad M., Guterch A., Keller G.R., Takács E.

Przegląd Geologiczny

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2006

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Vol. 54, nr 1

45-50

EN

The question of the eastern extent of the Variscan externides in the Polish Lowlands is a subject of ongoing scientific debate. The key to resolve this problem is to provide a good seismic image of the pre-Permian strata. Unfortunately, the industrial seismic profiling brings sparse information from below the Zechstein, thus in 2003, a special seismic experiment called GRUNDY 2003 has been organised. The acquisition system was based on the deep seismic sounding equipment and was targeted at the recognition of Palaeozoic strata. The results in form of the 3D tomographic velocity field and the migrated depth section form the basis for the geological interpretation. Deduced geological model suggests the existence of two different geological media below the Permian strata. The likely interpretation is that it is the contact zone of the Variscan externides with their foreland. Obtained results are of a great importance for the hydrocarbons exploration perspectives.

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Density-velocity relationship in the upper lithosphere obtained from P- and S-wave velocity models along the EUROBRIDGE'97 seismic profile and gravity data

Kozlovskaya E., Janik T., Yliniemi J., Karatayev G., Grad M.

Acta Geophysica Polonica

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2004

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Vol. 52, nr 4

397-424

EN

Traditionally, joint interpretation of seismic refraction and wide-angle reflection data and gravity data is based upon a well-known correlation between seismic P-wave velocity and density proved by numerous laboratory investigations of elastic properties of crustal rocks. One of the problems connected with this approach is that rocks with high content of calcium-reach plagioclase have higher P-wave velocity and do not satisfy the common density-Vp relationship. That is why joint interpretation based upon any conventional relationship between density and P-wave velocity cannot be applied to wide-angle profiles across large anorogenic rapakivi-gabbro-anorthosite massifs composed of rocks with high content of plagioclase. The problem can be solved if both P- and S-wave velocities are used to calculate the density model. The results of laboratory studies of rock properties demonstrate strong correlation between density and S-wave velocity. Moreover, the isotropic S-wave velocity seems to be generally more correlated to density than the P-wave velocity and less affected by high content of plagioclase. In spite of that, the known relationships connecting density to S-wave velocity or to both P- and S-wave velocities are very seldom used for joint interpretation of seismic and gravity data. The main reason for this is a lower quality of S-wave arrivals in explosion seismology, which makes it difficult to obtain reliable S-wave velocity models. In our paper we present the results of joint interpretation of seismic and gravity data collected along the EUROBRIDGE'97 wide-angle reflection and re-fraction profile in the Ukrainian Shield, where the absence of thick sediments made it possible to obtain both P- and S-wave velocity models. To calculate the density model along the EUROBRIDGE'97 profile we used a method of gravity data inversion, in which the density model was parameterised by the relationship connecting density to both P- and S-wave velocity models. Such a parameterisation makes it possible to obtain the relationship between density and seismic velocities by inverting the gravity data. As a result, non-linear and scattered relationship between density and seismic velocities was obtained for the EUROBRIDGE'97 profile. Analysis of the relationship demonstrated that the reason for this scattering is difference in density-velocity relationships for large-scale geological units crossed by the profile. In order to explain this difference, we compared the relationship between seismic velocities and density in three major geological units crossed by the EUROBRIDGE'97 profile with the petrophysical data from the Ukrainian Shield and other selected Precambrian areas. We demonstrated that the deviations from the averaged density-velocity relation-ships can be explained by specific mineral composition of rocks resulting from different age and conditions of crust formation. We showed how the analysis of density-velocity diagrams can be used to restrict the composition of the crust and, in particular, the composition and metamorphic grade of the lower crust.

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Struktura głębokiego podłoża Karpat w oparciu o kompleksową interpretację danych geofizycznych

Królikowski C., Młynarski S.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2003

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T. 29, z. 3--4

197-218

PL

W pracy przedstawiono model budowy litosfery w polskich Karpatach. Jest on oparty na wynikach kompleksowej interpretacji wzdłuż profilów magnetotellurycznych (MT) i sejsmiki refrakcyjnej. W wyniku interpretacji sejsmicznych profili refrakcyjnych wyznaczono przebieg granicy sejsmicznej wiązanej z podłożem krystalicznym. Oś depresji karpackiej i linie nieciągłości grawimetrycznych wskazują na istnienie strefy oddzielającej segment zachodni od segmentu wschodniego polskich Karpat. Wyniki modelowań grawimetrycznych wzdłuż profilów MT wydają się potwierdzać różnice strukturalne w obydwu segmentach. Stwierdzono względnie płaski przebieg nieciągłości Moho w segmencie zachodnim i jej znaczne zagłębienie w segmencie wschodnim.

EN

In the paper a model of lithosphere structure in the Polish Carpathians is presented. It is based on results of an integrated interpretation along the magnetotelluric (MT) and seismic refraction profiles. As a result of the refraction data reinterpretation, a seismic horizon related to the top of the crystalline basement is described. An axis of the Carpathian gravity depression and main sequences of gravity discontinuities show the existing in the Polish Carpathians of an important zone separating the western part (segment) from the eastern one. Results of the gravity modeling along the MT profiles seem to prove the structure differences in both of the segments. A relatively flat Moho discontinuity in the western segment and its significant lowering in the eastern one were started as well.

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Geofizyczno-geologiczne badania stropu i nadkładu wysadu solnego "Damasławek"

Krzywiec P., Jarosiński M., Twarogowski J., Burliga S., Szewczyk J., Wybraniec S., Czapowski G., Zientara P., Petecki Z., Garlicki A.

Przegląd Geologiczny

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2000

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Vol. 48, nr 11

1005-1014

PL

Celem prowadzonych prac było określenie budowy geologicznej czapy anhydrytowej oraz nadkładu wysadu solnego " Damaslawek". Podstawowym narzędziem badawczym były wysokorozdzielcze dane sejsmiki refleksyjnej. Dodatkowo wykonano pomiary i interpretację danych geoelektrycznych, oraz reinterpretację archiwalnych danych grawimetrycznych i geofizyki otworowej. Uzyskane dane sejsmiczne charakteryzowały się wysoką jakością. Zintegrowana interpretacja geofizyczno-geologiczna pozwoliła na bardzo precyzyjne określenie głównych i podrzędnych deformacji tektonicznych, rozwiniętych w obrębie czapy oraz w jej nadkładzie. Zidentyfikowano wiele reaktywowanych uskoków inwersyjnych, które najprawdopodobniej przynajmniej częściowo były związane z ruchami przesuwczymi. Analiza sejsmostratygraficzno-tektoniczna pokazała, iż niektóre strefy uskokowe były aktywne również w czwartorzędzie.

EN

The goal of completed research project was to establish reliable geological model of cap rock and overburden of the "Damaslawek" salt dome. High-resolution reflection seismic profiling was main research method used for this project. Additionally, geoelectrical profiling and interpretation as well as reinterpretation of available gravity and well log data was completed. Acquired seismic data were of very high quality. Integrated geophysical-geological interpretation allowed the major and subordinate tectonic deformations present within cap rock and salt dome ś overburden to be precisely distinguished. Numerous inversion faults possibly at least partly related to strike-slip movements were identified. Seismostratigraphic-tectonic analysis showed that some of identified fault zones were active also during the Quaternary.