Regional Structural Geological Modeling Through Fault Data Correlation

Onshore projects often span extensive areas, and coarse, basin-wide models are used in activities such as assessing regional stress patterns and stratigraphic trends, as well as planning rig schedules. An onshore group required a higher level of detail than was in their existing model in order to fully analyze the structure and stratigraphy in their field; ultimately they required a basin-wide model which included multiple, highly detailed sections over each of their 3D seismic surveys.

The group selected EarthVision for the study because of its capability to easily handle the large number of small faults which needed to be modeled, its options for both manual and automatic fault tree building, and for the customization of individual fault blocks. The team started by building smaller, discrete structure models for the 3D seismic areas to capture the detailed geometry of the localized faults. The data from the small models was then exported and combined with the regional fault data. The larger basin-wide model was built from the combined dataset, and the result was a single model with hundreds of small, local faults from the 3D seismic surveys, as well as a dozen regional faults picked from published maps and regional 2D seismic data. With the finer scale details included in their basin-wide fault model, the team had a better understanding of how the faulting pattern was related between the separate 3D seismic survey areas (Figure 1).

Figure 1. Cross section view of the EarthVision model showing an area of localized faulting corresponding to an area with a 3D seismic survey.

For the model stratigraphy, initial focus was put into creating a marker horizon using thousands of well picks for that horizon, combined with the small areas of depth-converted seismic which were also tied to the well picks. With a marker bed in place, EarthVision was able to automatically isopach other horizons based on well picks and depth-converted seismic. Ultimately tens of thousands of well picks were used in the model. The EarthVision 3D Viewer was used extensively to filter and color the well picks to spot obvious and more subtle data busts. The team were able to easily generate a list of wells with data issues and used it for further QC. The cleaned-up picks were then substituted into the EarthVision model building process and the model was rapidly updated.

Figure 2. The completed regional model with vertical wells in blue and horizontal wells in pink.

Once the new structure model was in place, the group focused on a well analysis study (Figure 2). Using additional EarthVision tools and scripts, the team determined qualitative and quantitative information about the well relationships with each other, and with the model zones and faults, including:

  • zone and fault block labeling (intersections) for every point in every well trajectory
  • nearest well location
  • operator of the nearest well
  • nearest well that landed in the same model zone
  • length of the well that landed in the zone
  • all other model zones the horizontal legs were landed in
The well/model attributes were visualized both in 2D plots and in the 3D Viewer. After detailed QC of the well analysis data in EarthVision, it was straightforward for the team to bring the results into their Spotfire database to study with other elements; this enabled the group to determine which zones to target for future drilling programs.

The flexibility of EarthVision to incorporate areas of highly detailed localized fault data, with existing regional fault data, into a single basin-wide model was a critical step to completing a well analysis study. Tools within EarthVision facilitated investigating and understanding the relationships between the wells, faults and stratigraphy, and provided the team with the critical information they needed to plan for their future drilling program. Access to a scripted, repeatable workflow allowed the team to quickly and easily update their well analysis results as new wells were drilled.

See the EarthVision page for more information.

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