Modeling synrift sediment infill patterns of synthetic normal faults
Abstract
Previous studies of normal faulting and their control on sedimentation have largely focussed
on geometrical infill patterns from a two dimensional perspective. In order to overcome this a
series of 3D models have been generated which allow 3D infill patterns to be examined in
detail. This study uses a series of synthetic 3D experiments to highlight the effect of changing
fault displacement parameters on synrift sedimentation patterns. Several experiments have
been run using new functionalities in Roxar’s RMS 2013 software (part of their uncertainty
module), in particular the ability to change displacements within a structural model. A new
workflow has been established which combines the different RMS functionalities to
sequentially displace surface models and infill the resulting hanging wall depressions. This
workflow enables the user to manipulate various fault parameters, including length,
displacement field and reverse drag, plus the option to manipulate the number of faults and
their evolutionary geometry.
The modifications to the structural models make it possible to generate topographic surfaces
and displace them in a similar manner to faults cutting the earth’s surface. The resulting
hanging wall basins can then be infilled using flat surfaces. The displacement-infill sequence
forms a series of evolutionary models where the relative impact of the rate of the
displacement and sedimentation can be observed (these rates are user controlled). In RMS,
semi-automated modeling techniques were developed to accomplish various scenarios, which
allowed specific parameters to be altered and their impact assessed. The structural models
have been converted to 3D grids in order to utilise RMS’s visualization of layered/segmented
models and optimize the presentation of the results (successive time steps, layer geometries,
fault displacement view, map view and multi cross-section view).
Initial models concentrated on using a single fault model in order to test the RMS
functionalities. These models have been used to develop the RMS workflow and check the
resulting models produced the expected results. The initial experiments have been developed
to generate more complex structural situations in order to demonstrate how these techniques
can be applied to more real world scenarios. The more complex experiments include
asymmetric faults (where the point of maximum displacement is not in the center of the
fault), multiple faults with similar displacement rates and relay ramps. Finally, further
modeling techniques were developed in order to model the formation of sedimentary lobes
such as those in a Gilbert delta environment. These techniques include the use of cone-shaped
infill surfaces to mimic the radial sedimentation patterns associated with Gilbert type fan
deltas. These visualizations attempt to replicate field examples of synrift sedimentation from
the Corinth Rift in Greece (especially the Vouraikos Delta).
Description
Master's thesis in Petroleum geology