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Clay Smear: How Predictive Will we Ever Be? Insight From Sandbox Models and Seismic
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Fifth International Conference on Fault and Top Seals, Sep 2019, Volume 2019, p.1 - 5
Abstract
Summary
Clay smear is an important fault seal mechanism which controls fluid distribution in hydrocarbon fields. Although the idea is four decades old and extensive research and application in the subsurface has improved our understanding, predicting fault seal by clay smear remains a challenge. The complex architecture of fault zones and the difficulties of critically testing subsurface predictions calls for a challenge to the reliability of current methods. Empirical predictions rely on local calibration, but commonly actual findings are quite different from predictions. The objective of this paper is to share some pioneering sandbox experiments 25 done years ago to determine the structural processes and physical parameters that control clay smear formation. Two modes of clay smear formation have been modelled: injection and smear. The mode is determined by the contrast in strength between the clay and the surrounding rocks. If the strength contrast is low (relatively strong clay layer), no injection occurs, and the fault zone is a sheared equivalent of the faulted stratigraphy. If the strength contrast is high enough (soft clay), injection of clay into the fault zone is triggered. These experimental results led to the development of the squeezing block concept of clay injection.
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