Direct Measurement and Analysis of Structural Data using Photorealistic Outcrop Models, Somerset, United Kingdom

Paul Gillespie¹, John B. Thurmond², Melina Vartdal³, and Roald Farseth^2
1 Hydro Oil & Energy Research Center, Sandsliveien, Norway
² Hydro Oil & Energy Research Center, Bergen, Norway
³ University of Bergen, Bergen, Norway

Exploration and production of structurally complex reservoirs.in extensional settings requires a high degree of knowledge about fault-related folding of sedimentary units as well as about the size distribution of normal faults. While seismic studies can provide excellent 3-D information, they can suffer from limited resolution and a lack of kinematic data. Outcrop data provide much greater resolution, but they are usually limited to 2-D maps and sections. In this study we digitally captured cliffs and a well-exposed foreshore from an excellently exposed system of normal faults in Somerset in order to interpret faulting and folding in 3-D with high resolution.

The study area is located in Somerset, UK, where Lower Jurassic limestones and marls crop out both in 30m cliffs and in a 250m broad foreshore. A precise three-dimensional model of the outcrop was built, using precise integration of data from LIDAR scanning and high-resolution oblique photography. A line-sampled fault displacement population shows a power law down to 25cm, which represents the lower bound of measurable offset resolution on the photorealistic model. The juxtaposition of a well-established stratigraphic framework, a 3D photorealistic model of appropriate resolution and scope, and a suitable interpretation environment yields rapid, detailed and accurate results that allow the spatial relationship between various types of folding and faulting to be defined. Using these data, the fault displacement gradients can be related to the degree of folding in a predictive way.