Reverse-time modeling of channelized meandering systems from geological observations

in: 2018 Ring Meeting, ASGA

Abstract

Meandering systems shape the sub-aquatic and terrestrial landscapes by their temporal and spatial evolution. Witnesses of this evolution can be observed on the plains crossed by these channels. Among them, lateral point bars result from the channel migration, abandoned meanders are created by stream rectifying and abandoned channels originate from avulsion. Once buried, channelized systems are good candidates for natural resources storage thanks to the diversity and the volume of the resulting deposits. The understanding of the internal architecture of facies is thus crucial for resource exploitation. Satellite and LIDAR (Light Detection and Ranging) images permit current system studies. Subsurface architecture can be imaged by seismic or GPR (Ground Penetrating Radar) images. These techniques give a good evaluation of the whole system last channel path. However, anterior stages, when spared by the erosion, can only be observed locally. Indeed, the reworking of the channel belt by lateral and downstream migration makes it difficult to observe the geometrical or chronological features of anterior deposits. Borehole data can also inform locally about the encountered facies. We propose a simulation method of channelized systems conditioning to sparse and diverse available information. Among them, the subsurface imaging often permits to identify the last system stage and the abandoned meanders, thanks to their muddy filling after the abandonment time, that contrasts with the channel belt. Lateral point bars can also be observed, witnessing of meander paleo-migration direction. Sometimes, well data inform on the facies (e.g., muddy, sandy). The method presented here starts from the last channel path observed on the seismic image and goes back in time by reverse migration to reconstruct anterior channel paths. This stochastic migration model is inspired by the analysis of historic Mississippi maps. According to a chronology simulation based on spatial and statistical criteria (e.g., distance and orientation to the current channel, abandonment probability distribution), abandoned meanders are integrated at the relevant time step inside the main channel path. The issue of not imaged abandoned meanders, due to erosion, low image resolution or lack of imaging, is addressed by abandoned meander simulation inside the meander belt. This stochastic simulation conditions to geometrical criteria observed on the abandoned meanders spared by the erosion, but also to statistical criteria observed on sedimentary analogs such as the Mississippi river (e.g., erosion probability distribution). The simulation of abandoned meanders opens the way to conditioning borehole data by simulating a loop around or on the well location depending on the observed facies.

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BibTeX Reference

@INPROCEEDINGS{,
    author = { Parquer, Marion and Collon, Pauline and Caumon, Guillaume },
     title = { Reverse-time modeling of channelized meandering systems from geological observations },
 booktitle = { 2018 Ring Meeting },
      year = { 2018 },
 publisher = { ASGA },
  abstract = { Meandering systems shape the sub-aquatic and terrestrial landscapes by their temporal and
spatial evolution. Witnesses of this evolution can be observed on the plains crossed by these
channels. Among them, lateral point bars result from the channel migration, abandoned meanders
are created by stream rectifying and abandoned channels originate from avulsion. Once buried,
channelized systems are good candidates for natural resources storage thanks to the diversity and
the volume of the resulting deposits. The understanding of the internal architecture of facies is
thus crucial for resource exploitation.
Satellite and LIDAR (Light Detection and Ranging) images permit current system studies.
Subsurface architecture can be imaged by seismic or GPR (Ground Penetrating Radar) images.
These techniques give a good evaluation of the whole system last channel path. However, anterior
stages, when spared by the erosion, can only be observed locally. Indeed, the reworking of the
channel belt by lateral and downstream migration makes it difficult to observe the geometrical
or chronological features of anterior deposits. Borehole data can also inform locally about the
encountered facies.
We propose a simulation method of channelized systems conditioning to sparse and diverse
available information. Among them, the subsurface imaging often permits to identify the last
system stage and the abandoned meanders, thanks to their muddy filling after the abandonment
time, that contrasts with the channel belt. Lateral point bars can also be observed, witnessing of
meander paleo-migration direction. Sometimes, well data inform on the facies (e.g., muddy, sandy).
The method presented here starts from the last channel path observed on the seismic image and goes
back in time by reverse migration to reconstruct anterior channel paths. This stochastic migration
model is inspired by the analysis of historic Mississippi maps. According to a chronology simulation
based on spatial and statistical criteria (e.g., distance and orientation to the current channel,
abandonment probability distribution), abandoned meanders are integrated at the relevant time
step inside the main channel path. The issue of not imaged abandoned meanders, due to erosion,
low image resolution or lack of imaging, is addressed by abandoned meander simulation inside
the meander belt. This stochastic simulation conditions to geometrical criteria observed on the
abandoned meanders spared by the erosion, but also to statistical criteria observed on sedimentary
analogs such as the Mississippi river (e.g., erosion probability distribution). The simulation of
abandoned meanders opens the way to conditioning borehole data by simulating a loop around or
on the well location depending on the observed facies. }
}