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StructureSolver lets you create balanced forward models of the hangingwall structures associated with movement on faults.
You can interactively change the models until you have matched the observed structures in your seismic or geologic section.
Through this process you create value by:
- Constraining fault shapes and cross-fault correlations
- Clarifying structural kinematics and the interplay between faulting and sedimentation.
- You can simply create a structural model based on any fault in your Interpretation.
- StructureSolver rigorously incorporates scientific principles to model the folding that takes place in the hangingwalls of growth faults.
- StructureSolver seamlessly integrates structural growth and sedimentation so you can model both extensional and contractional growth structures.
- You can simply control all principal variables while continuously overlaying the resulting model over a seismic or geological cross section.
- This multi-variable interactivity helps you to quickly gain insights into the structures you are modeling.
Mississippi Canyon Structural Model
This example illustrates how StructureSolver analysis can create value when analyzing large extensional growth faults, such as those found in the Gulf of Mexico and other passive continental margins. In such systems, the fault traces themselves may be well imaged using modern seismic data. Stratigraphic correlations may be well established from well control in the shallow section but unknown in the deeper section. Such systems often have very large displacements and interpreters quite often underestimate the amount of growth in the deep section.
In this example, StructureSolver is used to confirm the upper level stratigraphic correlations and to confirm and refine the fault shape. The combination of convex and concave curvatures on the fault provides significant geometric constraints. After this is done, a good estimate of the deeper stratigraphic correlations is readily obtained.
In some sections we have studied, there was very early salt movement in the core of the extensional growth structure. In such cases, careful analysis of discrepancies between the deep modeled and observed geometries can help you estimate the amount and timing of salt movement.
Step-by-step Sequence of Analysis
- You simply choose to add structural surfaces to any fault in your interpretation.
- StructureSolver will automatically configure the set of kink axes that control the deformation within the hangingwall of the fault, and will let you add undeformed structural surfaces using mouse movements and clicks.
- You can subsequently deform the shapes of the surfaces you have added by modifying your structural model.
- Add new surfaces to an already partially constructed and deformed structural model
- Delete or redefine structural surfaces.
- Modify the shape of the controlling fault using any interpretation function.
- Manipulate structural surfaces using the functions Stretch Overlying Layers, Move Underlying Layers and Move Individual Surface
- Change the deformation shear angle in real time
You will typically use StructureSolver to model actual structures that are visible on an image of a seismic or geologic section.
The flexibility with which you can create and modify models creates many different opportunities for creative use.
If footwall and hangingwall strata are well-defined in both geometry and correlation, you can use StructureSolver to refine the fault shape.
- Interpret a first estimate of the fault geometry.
- Add structural surfaces and set the footwall reference levels to their observed levels.
- Move the hangingwall reference points so that the hangingwall reference levels are matched, or alternatively so that the hangingwall cutoffs are matched.
- If you are confident of the hangingwall cutoffs you may wish to lock them at this stage.
- Refine the fault shape until the entire hangingwall geometry is matched.
- The overall hangingwall fold dimension will constrain the dip on the deepest parts of the fault.
- Details of normal and reverse "drag" near the fault will constrain details of minor convex and concave bends in the fault.
If the fault and hangingwall geometries are well constrained, you can use StructureSolver to define the correlations across the fault.
- Interpret the fault
- Add structural surfaces at the hangingwall reference levels.
- Adjust the footwall reference levels until the hangingwall rollover geometry and cutoffs are matched.
StructureSolver can be very effective at analyzing systems of faults. You should start by modeling the gross geometry of each major fault. This helps you understand the overall kinematic picture and the interaction of faults in time and space.
StructureSolver modeling also often does a good job of approximating the displacement patterns of synthetic and antithetic faulting in the hangingwalls of large faults. Thus while you a modeling a single large fault you can gain important insights into the formation of the minor faults within its hangingwall.
Rhone Delta Structural Model
The seismic section from the Rhone Delta extension shows a complex extension patten above a shallow dipping weak detachment.
Despite the structural complexity most of the structural development can be modeled using two listric faults.
- Movement on the left fault generally predates movement on the right fault, although there is a period of overlap. The left fault has a simple listric shape. The net effect of growth across this fault is simple rotational fanning.
- The right fault has a convex pillow superimposed on its overall listric shape (probably associated with movement on the left fault). Synthetic deformation axes associated with this pillow produce the pronounced syncline. The structural deformation pattern could not be effectively modeling without taking into account both synthetic and antithetic shear axes. In the observed section there are numerous small synthetic faults whose patten matches the modeled shear pattern.
The modeling quite strongly constrains the correlations across both faults.
Data courtesy of TGS-Nopec.
StructureSolver can handle contractional growth structures fairly well. The geometry of the kink axes does not conform to flexural slip deformation however. A fairly steep (nearly 90 degree) shear angle gives a good overall approximation for contractional growth structures. Future versions of StructureSolver may incorporate more sophisticated definitions of contractional deformation axes.
Lost Hills Contractional Growth Structure
In this example StructureSolver is used to model a contractional growth structure, approximately duplicating the model produced by Don Medwedeff for the Lost Hills Anticline.
A near vertical shear angle is used to approximate flexural slip folding. Nevertheless the main features of Medwedeff's model are rapidly reproduced. A good estimate of the deeper fault ramp is also obtained.
In a similar way StructureSolver can be used to model the deepwater contractional growth structures that are found offshore the Gulf Coast and offshore parts of West Africa.
Cross-section image from Medwedeff, D. A., 1989,"Growth Fault-Bend Folding at Southeast Lost Hills, San Joaquin Valley, California": AAPG Bulletin, Volume 73-1, pages 54 - 67.
- You interpret faults, horizons and markers as simple curves identified with descriptive categories.
- Faults and horizons automatically have special properties for structural modeling and restoration. Markers are undifferentiated events.
- All drawing and curve editing functions apply equally to faults, horizons and markers and require minimal specification:
- You can simply set the active curve category for drawing by clicking on an existing curve or by selecting from a list.
- You can modify or delete any point on any curve in a single editing operation
- To add points, split, or join curves, you first identify curve segments with a single click
- You can easily delete or reassign curves and delete or redefine entire curve categories.
- No special preparatory steps are needed before creating or modifying a structural model or performing a structural restoration.
- When you edit a fault that has structural model, the model automatically changes.
- All graphical operations use a consistent set of mouse movements and clicks.
- Real-time instructions are shown in a status bar and dynamic information is shown in a dynamic label that follows the cursor
- StructureSolver does not have in-built functions to import digital interpretations, because of the wide variety of formats that would need to be supported.
- If you have an interpreted seismic or geologic section in another system, the best approach is to save an image of the interpreted section and then import that image into StructureSolver. You can then very rapidly draw over the existing interpretation with new active faults and horizons. In almost all circumstances this approach is quicker than a digital export/import procedure.
- For customers who have recurrent requirements to transfer digital interpretations from another system, we can assist in writing file transfer utilities that will write data to and from StructureSolver solutions data format.
- Absolutely. Individual faults can each have their own structural models and can also offset horizons that are selected for restoration.