Journal Article

FZJ-2018-05542

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Joint inversion of long-offset and central-loop transient electromagnetic data: Application to a mud volcano exploration in Perekishkul, Azerbaijan

Haroon, A. ; Adrian, J.FZJ* ; Bergers, R. ; Gurk, M. ; Tezkan, B. ; Mammadov, A. L. ; Novruzov, A. G.

2015
Wiley-Blackwell Oxford [u.a.]

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Please use a persistent id in citations: doi:10.1111/1365-2478.12157

Abstract: Mud volcanism is commonly observed in Azerbaijan and the surrounding SouthCaspian Basin. This natural phenomenon is very similar to magmatic volcanoes butdiffers in one considerable aspect: Magmatic volcanoes are generally the result ofascending molten rock within the Earth’s crust, whereas mud volcanoes are characterisedby expelling mixtures of water, mud, and gas. The majority of mud volcanoeshave been observed on ocean floors or in deep sedimentary basins, such as those foundin Azerbaijan. Furthermore, their occurrences in Azerbaijan are generally closely associatedwith hydrocarbon reservoirs and are therefore of immense economic andgeological interest. The broadside long-offset transient electromagnetic method andthe central-loop transient electromagnetic method were applied to study the innerstructure of such mud volcanoes and to determine the depth of a resistive geologicalformation that is predicted to contain the majority of the hydrocarbon reservoirsin the survey area. One-dimensional joint inversion of central-loop and long-offsettransient electromagnetic data was performed using the inversion schemes of Occamand Marquardt. By using the joint inversion models, a subsurface resistivity structureranging from the surface to a depth of approximately 7 km was determined.Along a profile running perpendicular to the assumed strike direction, lateral resistivityvariations could only be determined in the shallow depth range using thetransient electromagnetic data. An attempt to resolve further two-dimensional/threedimensionalresistivity structures, representing possible mud migration paths at largedepths using the long-offset transient electromagnetic data, failed. Moreover, thejoint inversion models led to ambiguous results regarding the depth and resistivity ofthe hydrocarbon target formation due to poor resolution at great depths (>5 km).Thus, 1D/2D modelling studies were subsequently performed to investigate the influenceof the resistive terminating half-space on the measured long-offset transientelectromagnetic data.The 1D joint inversion models were utilised as starting models for both the 1D and2D modelling studies. The results tend to show that a resistive terminating half-space,implying the presence of the target formation, is the favourable geological setting.Furthermore, the 2D modelling study aimed to fit all measured long-offset transientelectromagnetic Ex transients along the profile simultaneously. Consequently, 31252D forward calculations were necessary to determine the best-fit resistivity model.The results are consistent with the 1D inversion, indicating that the data are bestdescribed by a resistive terminating half-space, although the resistivity and depthcannot be determined clearly.

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Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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