- Home
- A-Z Publications
- First Break
- Previous Issues
- Volume 3, Issue 7, 1985
First Break - Volume 3, Issue 7, 1985
Volume 3, Issue 7, 1985
-
-
A combined dynamite - Vibroseis 3-D survey in the subalpine Overthrust zone of Austria
Authors K. Schimunek and E. StröblUnfavourable surface conditions and geological complexities have often prevented seismic exploration for oil and gas in areas of potential hydrocarbon reservoirs. An area in this category is located adjacent to the northern outskirts of Vienna. It is the so-called Overthrust F1ysch Zone. The mountainous topography, forests, dense population and a railway are all rather obstructive for a conventional 2-0 seismic survey. However, previously shot Vibroseis lines had revealed a structure which was subsequently drilled, and a natural gas reservoir of considerable economic value was found. The geology encountered in the weil Höflein 1 was from top to bottom as follows: F1ysch- Eocene to Upper Cretaceous to a depth of about 2000 m. The flysch layers dip steeply towards the south at angles up to 40°. Molasse- Miocene sediments dipping gently towards the south. The molasse has been overthrusted by the Ilysch nappes. Mesozoic- was encountered from 2500 to 3250 m. The gas was found in a Jurassic series called 'doloquartzarenite' at a depth of 2730 m. The overlying carbonates with an interval velocity of approximately 6000 m sec -1 give rise to a good reflection horizon which can be followed across the whole area. Basement- was hit at 3200m depth. It is composed of gneisses belonging to the Bohemian massif. In order to develop this gas field the decision was made to carry out a 3-D survey. However, the above mentioned surface conditions did not allow the use of a regular grid of source and receiver points, nor could a unique source, dynamite or Vibroseis, give uniform coverage over the area to be investigated. Thus, we were forced to the conclusion that it would be necessary to combine Vibroseis and dynamite to give an adequate practicallay out for use in the field. The project had to be regarded as a pilot survey because we know of no previous survey of this type. The survey was planned and performed by ÖMV geophysical department.
-
-
-
A multi-electrode array for resistivity surveying
Authors D.H. Griffiths and J. TurnbullTechniques for the interpretation of resistivity data collected over a horizontally layered earth have received a great deal of attention over the years and are now very successful. Even where the strata show some dip or gentle folding, or when other lateral variation occurs, useful results can often be obtained, but problems do arise when the geology departs too far from the horizontally layered model. However, the subsurface structure may be sufficiently uniform in cross-section to be treated as two-dimensional and, as the variation in apparent resistivity at the surface for any such subsurface distribution of resistivity can now be computed, the investigation of subsurface features of this type is in principle feasible. Two major difficulties have to be overcome in developing a practical technique for this purpose, one instrumental and one interpretational. We believe we have solved the first problem: we have also made some progress with the second.
-
Volumes & issues
-
Volume 42 (2024)
-
Volume 41 (2023)
-
Volume 40 (2022)
-
Volume 39 (2021)
-
Volume 38 (2020)
-
Volume 37 (2019)
-
Volume 36 (2018)
-
Volume 35 (2017)
-
Volume 34 (2016)
-
Volume 33 (2015)
-
Volume 32 (2014)
-
Volume 31 (2013)
-
Volume 30 (2012)
-
Volume 29 (2011)
-
Volume 28 (2010)
-
Volume 27 (2009)
-
Volume 26 (2008)
-
Volume 25 (2007)
-
Volume 24 (2006)
-
Volume 23 (2005)
-
Volume 22 (2004)
-
Volume 21 (2003)
-
Volume 20 (2002)
-
Volume 19 (2001)
-
Volume 18 (2000)
-
Volume 17 (1999)
-
Volume 16 (1998)
-
Volume 15 (1997)
-
Volume 14 (1996)
-
Volume 13 (1995)
-
Volume 12 (1994)
-
Volume 11 (1993)
-
Volume 10 (1992)
-
Volume 9 (1991)
-
Volume 8 (1990)
-
Volume 7 (1989)
-
Volume 6 (1988)
-
Volume 5 (1987)
-
Volume 4 (1986)
-
Volume 3 (1985)
-
Volume 2 (1984)
-
Volume 1 (1983)