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Magnetotellurics case history: frontier basin analysis (Amazon Basin, Colombia) (view source)
Revision as of 23:05, 17 January 2014
, 23:05, 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
}}
A regional exploration program to study a large unexplored area in the Colombian Amazon basin was conducted by Amoco Production Company in 1987 and 1988.<ref name=ch16r2>Burgett, W., A., Orange, A., Sigal, R., F., 1992, Integration of MT, seismic, gravity, and magnetic data for reconnaissance of the Colombian Amazon: 54th meeting, European Association of Exploration Geophysicists, Expanded Abstracts, p. 428–499.</ref> This study area was very large [approximately 300,000 km<sup>2</sup> (115,000 mi<sup>2</sup>)] and remote with dense jungle cover, rugged terrain, and limited road access.
The first phase of the program consisted of 31,700 km (19,700 mi) of airborne gravity and [[magnetics]]. The large-scale structures delineated in these surveys were then further investigated by MT The MT survey was feasible with a light helicopter because the crew was small and equipment was light and compact. Data were collected from 43 sites, with a typical spacing of 10–20 km (6–12 mi).
==Survey results==
The MT data clearly delineated a thick sedimentary section with internal units that could be correlated from site to site. Three resistivity “packages” were observed:
* 40–100 ohm-m (sedimentary)
* 150–250 ohm-m (sedimentary)
* >1000 ohm-m (crystalline basement)
The figure below shows a simulated cross section in the Amazon basin based on MT data.
[[file:applying-magnetotellurics_fig16-5.png|thumb|{{figure number|16-5}}Drafted from data in .<ref name=ch16r2 />]]
==Post-MT program==
Encouraged by the evidence from the MT survey, Amoco decided to shoot a small seismic program and drill a shallow stratigraphic test. This program was positioned on the edge of a subbasin defined in the MT data. There generally was good agreement between the MT data, the seismic data, and the borehole geology.
The airborne gravity and magnetic data, followed by the surface MT survey, provided a very cost-effective means of regional basin definition and led directly to a well-positioned seismic survey and well site.
==See also==
* [[Overview]]
* [[What is Magnetotellurics (MT)?]]
* [[What does an MT survey measure?]]
* [[How are MT data acquired?]]
* [[Case history: rugged carbonate terrain (Highlands of Papua New Guinea)]]
* [[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
}}
A regional exploration program to study a large unexplored area in the Colombian Amazon basin was conducted by Amoco Production Company in 1987 and 1988.<ref name=ch16r2>Burgett, W., A., Orange, A., Sigal, R., F., 1992, Integration of MT, seismic, gravity, and magnetic data for reconnaissance of the Colombian Amazon: 54th meeting, European Association of Exploration Geophysicists, Expanded Abstracts, p. 428–499.</ref> This study area was very large [approximately 300,000 km<sup>2</sup> (115,000 mi<sup>2</sup>)] and remote with dense jungle cover, rugged terrain, and limited road access.
The first phase of the program consisted of 31,700 km (19,700 mi) of airborne gravity and [[magnetics]]. The large-scale structures delineated in these surveys were then further investigated by MT The MT survey was feasible with a light helicopter because the crew was small and equipment was light and compact. Data were collected from 43 sites, with a typical spacing of 10–20 km (6–12 mi).
==Survey results==
The MT data clearly delineated a thick sedimentary section with internal units that could be correlated from site to site. Three resistivity “packages” were observed:
* 40–100 ohm-m (sedimentary)
* 150–250 ohm-m (sedimentary)
* >1000 ohm-m (crystalline basement)
The figure below shows a simulated cross section in the Amazon basin based on MT data.
[[file:applying-magnetotellurics_fig16-5.png|thumb|{{figure number|16-5}}Drafted from data in .<ref name=ch16r2 />]]
==Post-MT program==
Encouraged by the evidence from the MT survey, Amoco decided to shoot a small seismic program and drill a shallow stratigraphic test. This program was positioned on the edge of a subbasin defined in the MT data. There generally was good agreement between the MT data, the seismic data, and the borehole geology.
The airborne gravity and magnetic data, followed by the surface MT survey, provided a very cost-effective means of regional basin definition and led directly to a well-positioned seismic survey and well site.
==See also==
* [[Overview]]
* [[What is Magnetotellurics (MT)?]]
* [[What does an MT survey measure?]]
* [[How are MT data acquired?]]
* [[Case history: rugged carbonate terrain (Highlands of Papua New Guinea)]]
* [[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]]