AAPG Middle East Geoscience Technology Workshop, Integrated Emerging Exploration Concepts

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The Deliberate Search for Stratigraphic Traps in the Middle East. What Can We Learn from Global Stratigraphic Plays

Abstract

The ability for stratigraphic traps to deliver the worlds future energy demands remains undoubted.  Through a century or more of active global exploration the industry has had a primary focus on lower risk structural traps.  Now, however, as technology has improved, especially imaging techniques, and our appreciation of depositional controls the number of stratigraphic plays being explored has increased. Through a study of more than 600 well-documented stratigraphic and subtle combination traps from around the world we will share a number of global analog case studies and discuss some observations and ideas that may guide future exploration campaigns for these traps styles. The term stratigraphic trap is inconsistently used across the Petroleum Geologist community. All agree a stratigraphic trap retains hydrocarbons due to changes of rock properties rather than faulting or folding only, or due to a change in fluid properties. Types of fluidic traps are also inconsistently used and the interaction between stratigraphic and fluidic traps is important in some giant fields, which will be demonstrated. Included in the broadest stratigraphic definition are trap styles that are four-way dip closed, e.g. carbonate reefs and paleogeomorphologic traps. For others a stratigraphic trap is one where the stock tank oil initially in place (STOIIP) cannot be calculated using a depth structure map alone e.g. a sand body that has lateral pinch out onto a high. We suggest these are a sub-class of the broader stratigraphic trap. Trap classifications is further complicated by combination or complex traps, which combine two or more trap styles (structural, stratigraphic or fluidic) depending on the contact depth. In this presentation a brief overview of all stratigraphic and subtle combination trap styles is provided. The focus will then shift to traps that require a component of up-dip lateral pinch out. Defining the sand body edge (trap gross rock volume uncertainty) and the up-dip seal (retention risk) is often problematic when evaluating these prospects. Eight major trap categories, which comprise sixteen individual trap types, were defined using this data set. The major trap categories include lateral depositional change, buried depositional relief, sub-unconformity truncation, buried erosional relief, onlap onto erosional surface, erosional trough fill, diagenetic and fluidic. Lateral depositional change, which includes lateral facies change and lateral depositional pinch-out, is the largest category. The second largest category is sub-unconformity truncation. The prospecting implications for stratigraphic traps in the Middle East will be shared and a view on the potential yet-to-find in the region will also be shared.