This document provides a user guide for a paleo-structure restoration module. The module allows restoration of multi-stage complex structures based on tectonic evolution principles. It quantitatively describes tectonic activity and demonstrates the evolution process in 3D models. The module uses tools like erosion restoration, inclined shear, flexural slip, unfolding and flattening beds to restore structures. Parameters for the tools and the restoration workflow are described.

1. User guide of paleo-structure restoration
module
1 Quick look
1.1 Introduction
Based on kinematic principles, all tectonic movements involved in the structural model could
be restored with full consideration of the tectonic evolution history. The processes and results
of the restoration can provide first-hand materials for studying the region's tectonic evolution,
and reference materials for studying the region's hydrocarbon migration history, which is
significant for the exploration and development of oil and gas.
 Restore multi-directional and multi-stage complex structures.
 Quantitatively describe tectonic activity intensity.
 Demonstrate the tectonic evolution process with 3D models.
 Construct balanced cross-sections of any orientation.
Fig.1- 1 The same layer model in different stage.

2. 1.2 Module relationships
The system can directly use the model established in the structural modeling module. The
resulting model can be opened and edited structural modeling module.
1.3 Workflow
The process of paleo-structure restoration is the process of using the tools, such as Erosion
restoration, Inclined shear, Flexural slip, Unfolding and Flattening beds to restore
different structures.
The steps are as follows:
1) Create an appropriate tool;
2) Set parameters used by the tool;
3) Implement the tool and obtain the result;
4) Export the result.
Fig.1- 2 Workflow.

3. 1.4 Theory
1.4.1 Principles and conditions of algorithm
Principles and conditions of using paleo-structure restoration module are as follows:
1) Rock volume is conserved during deformation.
2) Rock volume is only altered by erosion and sediment compaction.
3) Dominant deformation mode is brittle faulting.
4) Folding is related to faulting.
5) Volume losses attributed to pressure solution and tectonic compaction are assumed to be
minim.
1.4.2 Tool theory
There are four tools in the process of paleo-structure restoration, Erosion restoration,
Inclined shear, Flexural slip, Unfolding and Flattening beds. The theory would be
introduced in follows.
1) Inclined shear
The Inclined shear algorithm is effective for restoring normal faults.
A gap or void between the fault plane and the hanging-wall block is created by the extension.
The hanging-wall then collapses onto the fault plane. The collapse is controlled by the shear
vector, which is the specific path hanging-wall elements taken during the collapse. Thus
Inclined shear assumes deformation only occurs within the hanging-wall. The volume of the
hanging-wall is conserved during the restoration.

4. Fig.1- 3 Schematic diagram.
2) Flexural slip
The Flexural slip algorithm is used to restore the thrust fault.
It is assumed that deformation is restricted to the hanging-wall. Volume and area of the
hanging-wall beds are preserved, while footwall beds remain undeformed and are not
translated during the restoration.
Fig.1- 4 Schematic diagram.
3) Unfolding
The Unfolding tool is mainly used to restore upright folds formed by compression.
A pin plane and a folded range should be defined to determine the fold and its range to be
restored. A template plane should also be defined, which will be restored to horizontal state.
The area of the template plane and the volume of the model keep constant during the
restoration.

5. Fig.1- 5 Schematic diagram.
4) Flattening beds
The Flattening beds tool could restore the target surface to the datum along the reverse
process of the sedimentation, and could also restore the volume altered by sediment
compaction. The datum position, movement direction of the target surface, the initial porosity
and compacting factor of each horizon should be set before restoration. The area of the target
surface's projection is conversed during the restoration.
Fig.1- 6 Schematic diagram.
2 How to use the paleo-structure restoration tool
Please refer to the teaching video of paleo-structure restoration.
3 Special topic
3.1 Parameters introduction
1) Inclined Shear

6. Shear upper surface: is the target horizon, and corresponds to the" upper horizon" in fault
editing of Structure Modeling.
Generally, the Shear upper surface is set up according to the default, because the recovery
process always starts from the top of the model.
Shear lower surface: is the lower horizon affected by the fault, and corresponds to the" lower
horizon" in fault editing of Structure Modeling.
"NO" is the default option of software, which means the fault affected all horizon of the
model.
Shear vector:
Azimuth：it is the angle between shear vector and the north direction
Inclination：it is the angle between shear vector and the Z axis.
Fig.3- 1 (a)Azimuth, (b) Inclination.
By setting the Azimuth and Inclination parameters, guide he moving direction of the fault in
the process of structure restoration. Generally, we can use the default Azimuth and

7. Inclination parameters which can be obtained by calculated automatically according to the
position of fault in the model to calculate the model. You can modify the parameters properly
according to the research situation of the regional fault.
Surface and main fault would fit together as closely as possible when the surface is
restored：if the target fault was truncated, you need to select this function.
Shear plane：it is the plane that perpendicular to the fault strike, and located in the middle of
the fault.
2) Flexural Slip
Target surface to slide：it's the target horizon, and corresponds to the" upper horizon" in fault
editing of Structure Modeling.
Basement：it's the sliding datum in the process of restoration (As follows).
Fig.3- 2 Basement.
Movement hanging-wall: the hanging-wall would be moved, and the footwall has no
deformation during the restoration process.
Basement constraint: the deformation of the hanging-wall is constrained by the basement
form during the restoration process.
Movement direction of hanging-wall: it is the tendency of the fault.
Detachment fault group: it's the gather of all the fault in the hanging wall of the thrust fault.

8. Selecting the "Calculate slip fault" in the tree window, and then the Properties would be
increased an option of "Detachment fault group1" ,so we can choose the group according to
requirements.
3) Unfolding
Template plane：it is the target horizon default option is the top surface of the model in the
software.
Scoping in horizontal direction：It is a rectangular box in the model, and shows the scoping
of the fold control. We can adjust it by modifying the Forward and Reverse.
Fig.3- 3 The scoping of the fold control.
4) Flattening beds
Template plane：it is the target horizon.

9. Horizontal plane Z value：it is the datum position, which default value is 0.
De-compaction parameters：we need to set the initial porosity and compacting factor. There
are two ways to set, and default value is 0.
3.2 Denudation Restoration
3.2.1 Theory
"Reconstructing the strata denuded thickness" is the converse process of Denudation. Using a
series of methods to restore denuded thickness, structure form of purpose layer can be
restored to the form of no denudation.
Fig.3- 4 Schematic diagram.
3.2.2 Method
In view of the structure situation and the original data, we usually adopt the following two
methods：
Restore manually , using the method of stratum tendency extension
Restore automatically, according to the denudation amount data
Note: denudation thickness data is provided by customers, if there is no such data, denudation
thickness can be restored manually using the method of stratum tendency extension in
software.

10. 3.2.3 Operation
1) No data of denuded thickness
By using the method of seismic interpretation, interpreting manually the data of denudation
area (method as seismic interpretation module), and adding the data to the model data ,
updating the surface, completing restore denuded thickness.
2) Provide denuded thickness data
According to the data of denudation amount, the software can automatically recover
denudation thickness. The specific steps are as follows:
In software directory select the tool: EsCalThickness; ("EsCalThickness" is a tool of
Reconstructing the strata denuded thickness)
In the opening software window, select respectively Formation scatter file, Denudation
thickness and Results file path, and then click the Calculate button to generate the resulting
file
Discrete points file of the target horizon would be replaced by the result file, imported the
model. Update the horizon, and complete denudation recovery.

11. Fig.3- 5 comparison photo in before and after restoration.
3.3 Eliminate the distortion during the restoration
1) Problem description:
Sometimes there may be a distortion that impact the restoring effect of model because of
different displacement of fault during the restoration, as follows. If you want to directly to
restoration, it may beget a wrong calculating result, so you need to modify the model, and
then continue the follow-up work.
Fig.3- 6 The irregular fault line is the distortion near the red line.
2) Process Mode:
If there is some distortion (not limited to such distortion), it need us to Create a new mode in
the "tool name" node. And then continue the next work. Distortion can be eliminated by this
method.
Note: After creating a new model, it is necessary to adjust model boundary according to data
of discrete points, to ensure the changes of shrinkage and stretching quantity.

12. Fig.3- 7(a) Original data and boundary, (b) The data and the boundary in the new model.