There are a lot of structural geology modelling tools. Nevertheless, scientific work in collaboration with industry has shown me that available software is not cross-platform and has high costs and system requirements. Hence in 2018, with Rustam Zaitov we launched a startup project to design the Deform application to build balanced cross-sections and 2D structural restorations (Fig. 1).
Figure 1. Deform is a desktop application for 2D structural modelling.#
Deform allows the structural interpretation of seismic and field data, as well as the integration of ASCII data from different seismic and geological interpretation software. The quality control module provides cross-section interpretation validation and automatic error correction. Everything in the app is designed for high performance of geologists.
The beta-version of the application has been used by our research team in various commercial research projects, including the Novoport oilfield in Yamal Peninsula, Ni-Cu Talnakh deposit in Norilsk region, and Laptev sea. Additionally, it has been tested based on various published data relating to orogenic and extensional structures.
In 2023, we plan to launch Deform, which will work on Windows, Mac and Linux.
The quality control module includes short-line searches, connectivity analysis for faults, horizons and unconformities, as well as, the ability to correct errors automatically using the tidy tool. Thus, geologists can identify and fix potential line errors by trimming and extending objects. It is an essential step before cross-section balancing or structural modelling. Moreover, the application determines the nodes at the line intersections, allowing the export of validated data to any software.
The Wyoming Overthrust belt (modified from Williams and Dixon, 1985) data quality analysis is shown in Fig. 2. It indicates connectivity issues for horizons and faults that have been made in interpreting the seismic reflection profile. Errors are easily fixed with the automatic tidy tool.
Deform is the fastest way to build length-balanced cross-sections. The module allows to indicate flexural slip, measure bed lengths and straighten them to produce restored sections on stratigraphic frame without endless routine actions. Line-length balancing is suitable when stratigraphic thickness does not change during deformation and the shear is parallel to layers. Consequently, flexural-slip restoration is commonly used for contractional structures.
The line-length balancing workflow in Deform is shown in Fig. 3.
Figure 3. Line-length balancing workflow for a simple cross-section. #
In this case, a simple cross-section illustrates three thrust faults that emerge from a basal detachment (Figure 14-2 from Marshak and Mitra, 1988). Because the strata below the left-hand thrust are in place and are undeformed, a regional pin-line can be fixed in this fault block, where the purple bed serves as the datum. The next fault block is truncated by erosion, which is why the local pin-line is used to restore the layers into a stratigraphic frame. The horse is restored by measuring the bed lengths and the right-hand fault block is restored with a local pin-line that assumes no shear in the bend. Restoration of this cross-section shows that it cannot be balanced perfectly, as the orange bed is too short. Balance can be achieved in the app by adjusting the dip of the lower part of the right-hand thrust and increasing the length of the erosion thrust sheet’s orange bed. Alternatively, rather than increasing the length of the lower beds in the section, the higher beds in the section could be shortened.
Deform has been used successfully in line-length balancing of various structures, including those such as the Valley & Ridge within the Brown and Wills anticlines in the central Appalachians (Gwinn, 1964), the Mount Crandell Duplex within the Lewis Thrust Sheet in Waterton (Boyer and Elliott, 1982), the Pine Mountain thrust system within in the Powell valley anticline in the southern Appalachians (Mitra, 1988), the Oldman River triangle zone in the southern Alberta Foothills (Stockmal et al., 1996) and the Zagros fold-and-thrust belt within the Dezful Embayment (McQuarrie, 2004).
The restoration of a half-graben and tilted fault block structure in the northern North Sea (modified from Evans and Parkinson, 1983) is shown in Fig. 4.
Figure 4. Restoration of a half-graben and tilted fault block structure in the northern North Sea. #
The section’s notable features include the Magnus Ridge, which hosts the BP Magnus Field, as well as the North Shetland Trough. These structures extend northeast from the Shetland Islands basement platform and were formed by Middle Jurassic to Early Cretaceous dilational tectonics. The simple shear restoration of syn- and post-rift megasequences was carried out by an antithetic shear to the tilted fault block structure (inclined shear direction is 105°). The structural evolution model shows that the major structural growth occurred during the Early Cretaceous, characterised by the development of half-graben during the Late Cimmerian movements. Lower Cretaceous sediments onlapped this growing structure and were eventually inundated by the Turonian times. These Mesozoic tilted fault blocks provide the trapping structures for most of the major northern North Sea oil fields.
The application currently allows working with extensional structures, which are mostly characterised by straight normal faults. This approach has been successfully applied to structural modelling data from the North (Evans and Parkinson, 1983, Roberts et al., 1990), Barents (Faleide et al., 1984), and Laptev (unpublished data) seas. However, it is not suitable for simple shear hanging wall deformation modelling of listric normal faults and associated rollover folds. That is why we are currently focused on developing this feature within this module.
