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.