Understanding and Quantifying Object Scaling in 3d Outcrop Data

John B. Thurmond¹, James Archibald², Ian Lunt¹, and Ole Martinsen^1
1Research Centre Bergen, StatoilHydro, Bergen, Norway
²Department of Earth Science and Engineering, Imperial College, London, United Kingdom

A number of techniques have been developed for capturing 3D data from outcrops, which has resulted in a number of outcrops being ‘collected’ for subsequent viewing and analysis. The essential factor that separates a 3D outcrop data set that is simply an aesthetic simulacrum of a rock face from a data set that can be effectively used to better understand geology in 3D is an understanding of the scale of feature that is to be captured, and whether a particular outcrop is suitable to capture data at that scale. For example, it has been shown that tectonic faults tend to follow power-law scaling relationships that are consistent over a wide range of length scales, from the microscopic to the megascopic. So, when capturing 3D outcrop data for fault and fracture data, the essential scaling relationships can be derived from a 3D interpretation of an outcrop, almost regardless of the length scale of outcrop exposures being captured (within the limits of statistical population rules). However, the capture and analysis of 3D sedimentary features and bodies is much more complex, since these systems usually have a characteristic length scale. It is not be useful for 3D analysis to capture a tiny fraction of a large feature, nor to capture widely spaced single-dimensional outcrop faces to study a small-scale feature. A simple set of rules have been devised that specify what scale of feature will be captured from a specific outcrop exposure. Examples will be shown to illustrate this point and the proposed rules using both faulted/fractured outcrops and where an exemplary 3D outcrop exposure in shallow-marine/fluvial rocks captures few of the geometries of interest at any scale.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas