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Geologic Interpretation & Mapping
Structural and lithologic mapping forms the heart of MDA's geologic practice - with hundreds of geologic interpretations. MDA pioneered the concept of Virtual Field Trips in the late 1980's with the development of a 3-D mapping technology
Although our projects range from regional syntheses to prospect-level analysis, many of them have certain elements in common. First, we work with our clients to recommend a technical approach that can best meet the project's objectives and budget. These recommendations may concern the types of remote sensing data, the mapping scale, or special image processing to help identify various rock types and further enhance structural differentiation (see hard-to-assess areas).
Next, we integrate our interpretation of the surface geology with subsurface information such as potential field data, seismic data, and well log data. This data is often provided by our client, and assists us in providing a comprehensive, well-reasoned analysis.
Finally, we incorporate available ground truth information to improve the accuracy of our interpretation. This involves the MDA geologists conducting the field work for ground truthing themselves, training our clients' staff to complete this task, or completing the ground truth together with our client's staff.
Fracture Analysis
It is critical to identify areas with high fracture densities that may create unstable conditions during construction due to rockfalls or excessive groundwater infiltration.
Both density and orientation of fractures are important factors. Areas of high fracture density, especially where there is a high proportion of relatively open-standing fractures (those parallel to maximum principal compressive stress in most areas) are the most prolific.
Digital technology allows one to rapidly digitize fractures, compute and map fracture density, and analyze fracture orientation.
Virtual Field Trips
MDA pioneered the concept of Virtual Field Trips in the late 1980's with the development of a 3-D mapping technology that resulted in quantitative measurements. This technique involves integrating a digital elevation model (DEM) with high-resolution imagery to locate features in both horizontal and vertical space. This Quantitative Structural Mapping (QSM) technology has been used in Yemen to obtain hundreds of measurements of the top of the Umm Er Rhadhuma Formation in just one day. We also verified that the satellite imagery is very useful for mapping beds with very subtle dips (1 to 2 degrees) that are difficult to measure in the field. This approach reduces the amount of field work required, and increases exploration efficiency by identifying areas where particular attention is needed to resolve geologic questions.
These concepts evolved into our Quantitative Regional Visualization and Verification (QRVV) tool, which enables the user to visit a field site on a digital analytical stereo workstation. First, ground control points are chosen on a 3-D rendition of key marker beds. Then a three-point solution (TIN) is created using the x,y,z control points and the strike and dip of beds and other field characteristics can be calculated automatically. These measurements can be reprojected to recreate the marker bed geometry and identify potential hydrocarbon traps. They are also useful for calculating the true stratigraphic thickness of outcrops.
In a recently completed exercise for NASA, we found that when 1 meter resolution data is used, the accuracy of QRVV is within +/- 5 degrees of strike, and +/- 3 degrees of dip.
