Three-dimensional morphology of Diplocraterion and Ophiomorpha and their impact on reservoir properties

Abstract

The morphology of Ophiomorpha irregulaire and Diplocraterion is poorly understood in three dimensions, and their effects on reservoir quality are underappreciated. This Master's thesis focuses on morphological characteristics to aid in the identification of the trace fossils in cross section, and to form models of the trace-makers' behaviour, which is now understood to affect permeability. Understanding of the trace-makers' behaviour has led to a predictive understanding of sediment distribution within burrows and explains some morphological features. Based on the morphology and behaviour of modern day trace makers, Neotrypaea californiensis is an analogue trace-maker of O. irregulaire and Diplocraterion. Permeability measurements indicate that O. irregulaire reduces on average horizontal permeability (kh) by 28% and kv by 14%. Diplocraterion show an increase in permeability within the shafts and around the typical 'dumbbell' morphology relative to the matrix. Ophiomorpha and Diplocraterion have the potential to dramatically alter reservoir estimations and should be incorporated into reservoir characterisation studies.