Papua New Guinea MT: Looking where seismic is blind
- Univ. of California, Berkeley, CA (United States)
Hydrocarbon exploration in the Papuan fold belt is made extremely difficult by mountainous terrain, equatorial jungle and thick karstified Miocene limestones at the surface. The high-velocity karstified limestones at or near the surface often render the seismic technique useless for imaging the subsurface. In such areas magnetotellurics (MT) provides a valuable capability for mapping subsurface structure. Numerical and field data examples are presented which demonstrate the severity of the 1D errors and the improvements in accuracy which can be achieved using a 2D inverse solution. Two MT lines over adjacent anticlines, both with well control and seismic data, are used to demonstrate the application of 1D and 2D inversions for structural models. The example over the Hides anticline illustrates a situation where 1D inversion of either TE or TM mode provides essentially the same depth to base of Darai as 2D inversion of both TE and TM. The example over the Angore anticline illustrates the inadequacy of 1D inversion in structurally complex geology complicated by electrical statics. Four MT lines along the Angore anticline have been interpreted using 2D inversion. Three-dimensional modelling has been used to simulate 3D statics in an otherwise 2D earth. These data were used to test the Groom-Bailey (GB) decomposition for possible benefits in reducing static effects and estimating geoelectric strike in the Papua New Guinea (PNG) field data. It has been found that the GB decomposition can provide improved regional 2D strike estimates in 3D contaminated data. However, in situations such as PNG, where the regional 2D strike is well established and hence can be fixed, the GB decomposition provides apparent resistivities identical to those simply rotated to strike.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 438986
- Report Number(s):
- CONF-9206464-; ISSN 0016-8025; TRN: IM9711%%450
- Journal Information:
- Geophysical Prospecting, Vol. 44, Issue 6; Conference: 54. European Association of Exploration Geophysicists (EAEG) meeting, Paris (France), Jun 1992; Other Information: PBD: Nov 1996
- Country of Publication:
- United States
- Language:
- English
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