Yasuj
High Central Zagros (Iran), Part 1: Advanced Geophysical Integration
Henke, Christian H. (RWE Dea AG, New Ventures NA/ME) | Schober, Juergen (RWE Dea AG, New Ventures NA/ME) | Weber, Ulrich (RWE Dea AG, New Ventures NA/ME) | Gholami, Farnoush (N.I.O.C., Exploration Directorate) | Tabatabai, Hashem (N.I.O.C., Exploration Directorate)
Summary The hydrocarbon play of the Central Zagros was studied in an area of approximately 11,000km² in the vicinity of the townships Lordegan and Yasuj. The terrain is high mountainious with elevations from 900m to 4450m. Steep dips of surface and geologic strata pose a considerable obstacle to conventional seismic acquisition. In fact no seismic was ever acquired in the study area, except for two lines extending marginally into it. Key sections were selected for repeated acquisition of magnetotelluric (MT), wide-angle seismic (WARRP) and reflection seismic data, accompanied by detail surface geological analysis, dense area-wide gravity measurements and modern satellite image analyses including construction of a digital elevation model (DEM) (Figure 1). Magnetotelluric and WARRP were found to complement each other ideally, the first for the shallow parts and the latter for the deeper parts of a section. The combination of both methods worked well in complex tectonic terrain such as across the High Zagros Front Thrust where surface geology was integrated in the modelling. Integration of all geological and geophysical results led to a structural 3-D model of the study area, satisfying the measured gravity. Introduction The purpose of a combined geological and geophysical study in the High Central Zagros was to investigate the nature of the High Zagros Fault (HZF) and the structural styles in the adjacent fore- and hinterland. A second task was to investigate whether the prolific petroleum plays of the Zagros Foreland would extend into the study area and new petroleum plays could be recognized. While Bosold et al. (2005) published the geological study results this paper focuses on the geophysical part contributing to the solution of the geological questionnaire. Integration of seismic and potential field geophysical methods played a key role during this study (Henke et al. 2005). The area of investigation is located in the Zagros Fold-Belt ("Complex" Zagros Foreland) close to one of the oldest and richest oil and gas provinces in the world (Figure 1a) and the Zagros Thrust-Belt (High Zagros). Concepts and methods The study area is characterized by a high complexity in its geological and tectonic setting and is associated by an extremely rugged topography. The main and most difficult task was to acquire geophysical data that would be of good enough quality to allow a reasonable interpretation and validate the structural concepts in such a complex high mountainous environment. An analysis of available geophysical acquisition methods led the exploration team to an integrated approach. Only a combination of seismic and potential field geophysical methods was felt to be able to focus on the different depth levels and changes in the structural geology. New geophysical data A total of six profiles were selected that would allow testing of specific geological models and would be topographically accessible for certain geophysical acquisitions. A combination of different seismic and nonseismic methods were utilized and tested on these sections. The results of three magnetotelluric lines are presented as an example of the new acquired geophysical data. These lines in combination represent an idealized section through the entire study area.
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.49)
- Geophysics > Seismic Surveying > Seismic Processing (0.48)
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.34)
- Geophysics > Gravity Surveying > Gravity Acquisition (0.34)