Maximizing the Potential of the Digital Outcrop Revolution: The Automated Quantification of Fractured Carbonate Reservoir Analogues
Natural fracture systems commonly exert an important control on production from carbonate reservoirs. As seismic data do not have sufficient resolution to image most fractures, and borehole data have limited volumetric extent, prediction of subsurface fractures represents a major challenge. In this context, outcrop analogue studies often provide important supplementary information that reveals how fracture orientation, height and connectivity can vary as a function of depositional and/or diagenetic heterogeneity in a specific structural setting. While manual digitizing of fractures provides a reliable method for the interpretation of complex fracture patterns, it is a painstaking, time-consuming and sometimes subjective process. In this presentation we show how technology originally developed for 3-D seismic interpretation has been successfully adapted for the automated extraction of bedding and fracture data from remote sensing data. Examples are shown from world-class carbonate exposures in the Guadalupe Mountains (USA), Somerset (England) and the Middle East.
The examples of digital outcrop capture include both surface surveys and also subsurface surveys within tunnels. The analysed data include ground-based and airbourne LIDAR-derived photorealistic models and orthorectified Quickbird satellite imagery combined with satellite-derived digital elevation models. The examples have been chosen in order to 1) capture variability in terms of fractured carbonate reservoir types and structural setting, and 2) to develop and prove the technology using a range of remote sensing data types and different data qualities. The results derived from automatic analysis of the remote sensing data have been independently quality-controlled using traditional outcrop-based geological studies. We contend that the research has led to development of a rapid and robust method that allows for the extraction of statistically representative fracture populations. The new technology is a potential ‘game changer’ in the analysis of fractured reservoirs as it frees the structural geologist from laborious digitizing work and provides access to a plethora of relevant fracture data. The technology therefore allows the geologist to better focus on the interpretation and analysis of outcrop analogue data and to extract parameters for the building of discrete fracture network models.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009