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Magnetotellurics case history: rugged carbonate terrain (Highlands of Papua New Guinea) (view source)
Revision as of 23:06, 17 January 2014
, 23:06, 17 January 2014Initial import
{{publication
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Applying magnetotellurics
| frompg = 16-1
| topg = 16-12
| author = Arnie Ostrander
| link = http://archives.datapages.com/data/specpubs/beaumont/ch16/ch16.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
The Papuan thrust belt is both an expensive and difficult area in which to acquire seismic data. The area is typified by rugged mountainous terrain, dense equatorial jungle, and thick, heavily karstified limestone. The karstified limestone in some areas is also overlain by heterogeneous volcanics. The few coherent seismic reflectors are lacking in character and continuity, and the data in general are extremely noisy.
The sedimentary section in this area, however, is an excellent MT target.<ref name=ch16r1>Billings, A., J., Thomas, J., H., 1990, The use and limitations of non-seismic geophysics in the Papuan thrust belt, in Carman, C., J., Carman, Z., eds., Proceedings of the First PNG Petroleum Convention: Port Moresby, New Guinea, p. 51–62.</ref> This sequence observed in MT data is a simple three-layer package. The upper layer is the high-resistivity Darai Limestone, the middle layer is low-resistivity Leru Formation clastics, and the third layer is high-resistivity basement rocks. Therefore, the MT data provide a subsurface map of the base of the Darai and the top of the basement. The addition of an upper high-resistivity volcanic layer in some areas usually does not complicate this interpretation, except that it may not be possible to differentiate the base of the volcanics from the top of the Darai.
==Survey results==
More than 2,500 MT sites have been acquired in Papua New Guinea by numerous companies involved in exploration in the region (Mills, personal communication, 1994). BP Exploration (Hoversten, 1992) acquired MT data over both the Angore anticline and the Hides anticline. The interpreted models from these two data sets provide depth estimates of the base of the Darai Limestone to within 10% of the measured depth in the Angore 1 well. In both cases, the seismic data aided the interpretation.
The figure below shows the 2-D MT model beneath the Angore-1 well and the base of the Darai Limestone as observed in the well.
[[file:applying-magnetotellurics_fig16-6.png|thumb|{{figure number|16-6}}Drafted from data in Hoversten, 1992.]]
==See also==
* [[Overview]]
* [[What is Magnetotellurics (MT)?]]
* [[What does an MT survey measure?]]
* [[How are MT data acquired?]]
* [[Case history: frontier basin analysis (Amazon Basin, Colombia)]]
* [[Case history: Precambrian overthrust (Northwestern Colorado)]]
* [[Case history: volcanic terrain (Columbia River Plateau)]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch16/ch16.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Applying magnetotellurics]]
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Applying magnetotellurics
| frompg = 16-1
| topg = 16-12
| author = Arnie Ostrander
| link = http://archives.datapages.com/data/specpubs/beaumont/ch16/ch16.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
The Papuan thrust belt is both an expensive and difficult area in which to acquire seismic data. The area is typified by rugged mountainous terrain, dense equatorial jungle, and thick, heavily karstified limestone. The karstified limestone in some areas is also overlain by heterogeneous volcanics. The few coherent seismic reflectors are lacking in character and continuity, and the data in general are extremely noisy.
The sedimentary section in this area, however, is an excellent MT target.<ref name=ch16r1>Billings, A., J., Thomas, J., H., 1990, The use and limitations of non-seismic geophysics in the Papuan thrust belt, in Carman, C., J., Carman, Z., eds., Proceedings of the First PNG Petroleum Convention: Port Moresby, New Guinea, p. 51–62.</ref> This sequence observed in MT data is a simple three-layer package. The upper layer is the high-resistivity Darai Limestone, the middle layer is low-resistivity Leru Formation clastics, and the third layer is high-resistivity basement rocks. Therefore, the MT data provide a subsurface map of the base of the Darai and the top of the basement. The addition of an upper high-resistivity volcanic layer in some areas usually does not complicate this interpretation, except that it may not be possible to differentiate the base of the volcanics from the top of the Darai.
==Survey results==
More than 2,500 MT sites have been acquired in Papua New Guinea by numerous companies involved in exploration in the region (Mills, personal communication, 1994). BP Exploration (Hoversten, 1992) acquired MT data over both the Angore anticline and the Hides anticline. The interpreted models from these two data sets provide depth estimates of the base of the Darai Limestone to within 10% of the measured depth in the Angore 1 well. In both cases, the seismic data aided the interpretation.
The figure below shows the 2-D MT model beneath the Angore-1 well and the base of the Darai Limestone as observed in the well.
[[file:applying-magnetotellurics_fig16-6.png|thumb|{{figure number|16-6}}Drafted from data in Hoversten, 1992.]]
==See also==
* [[Overview]]
* [[What is Magnetotellurics (MT)?]]
* [[What does an MT survey measure?]]
* [[How are MT data acquired?]]
* [[Case history: frontier basin analysis (Amazon Basin, Colombia)]]
* [[Case history: Precambrian overthrust (Northwestern Colorado)]]
* [[Case history: volcanic terrain (Columbia River Plateau)]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch16/ch16.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Applying magnetotellurics]]