An Integrated Approach to Imaging and Interpreting Minor Faults in the Evaluation of Hydrocarbon Migration

By

Ravi K Singh¹

(1) Saudi Aramco, Dhahran, Saudi Arabia

 Seismic attributes, 3D visualizations and subsurface geological data were used to interpret minor faults and to investigate the stress field orientations in the Rub’ al-Khali basin of Saudi Arabia. An area southwest of Gahwar covering the Shama-Murradaf anticline trend was investigated. The work focused on the effectiveness of seismic 3-D volume interpretation, visualization techniques, seismic attributes and use of well data in imaging and mapping faults in the Permian systems.

The interpretation revealed a detailed fault pattern demonstrating complex fault zones consisting of several fault blocks. In addition to predominant N-S oriented faults E-W trend fault systems were identified. These E-W fault systems offset the regional N-S fault systems. The younger faults have small amounts (5-100 feet) of vertical displacements that are difficult to see on the conventional vertical seismic data but were delineated using attributes volumes. The faults appear to be left lateral and show local lateral movements of up to five kilometers on the seismic time slices. Since a horizontal stress direction perpendicular to, or an angle to these lateral faults could enhance the fault seals, the dipmeter and FMI data were investigated to identify the principal stress direction. Additionally, the fault dynamics, particularly cataclasis and cementation processes, were considered in evaluating the fault seals.

The positive results from the study have improved our knowledge of the regional and local stress field orientations. The integrated method provided for the mapping of faults with small displacements, and for the investigation of their sealing properties.