The Structural Habitat of Hydrocarbon Accumulations of Iraq

Thomas J. Frantes¹, Ayad F. Abbas², R.P. George³, and Tayfoor Rushdi^2
1ExxonMobil Exploration Company, Houston, TX
²Iraq Oil Exploration Company, Iraq
³ExxonMobil Exploration Company,

The vast hydrocarbon resources of Iraq (discovered: 134 GOEB [OPEC, 2004]; undiscovered: 65 GOEB [USGS, 2000]) are distributed across a broad range of structural habitats that are the products of: (1) basement grain and faults within its Precambrian continental crust, (2) distribution of Hormuz Salt, (3) “Hercynian” orogeny, and (4) creation of Tethyan passive and transform margins and their destruction resulting from their collision with Eurasia. These tectonic events have given rise to the distinctive structural styles of Iraq's four main hydrocarbon provinces. Using several key seismic examples we present new insights on the structural partitioning of Iraq and the implications for hydrocarbon distribution.
The structural habitat of Zagros-influenced traps consists primarily of fault-propagation folds fed by slip on Jurassic detachments (~39 GOEB). Hydrocarbon accumulations in the Mesopotamian Basin are found in two distinctly different settings. Accumulations in Central Iraq (~ 23 GOEB) occur in structures strongly influenced by basement-involved faulting, whereas the large anticlines of Southern Iraq (~71 GOEB), which are largely unfaulted and exhibit gently-dipping flanks, are the result of the reactivation of Precambrian structures and the evacuation of Hormuz Salt from neighboring synclines. Finally, the Western Desert of Iraq (~1 GOEB), which is largely unexplored, has Paleozoic-sourced exploration targets found at relatively shallow depths due to Mesozoic tilting and uplift, followed by extension.
The diversity of Iraq's structural habitats, and their impact on the relevant hydrocarbon systems, underscore the importance of placing exploration targets in their proper structural context. Unlocking the hydrocarbon potential of Iraq will require meeting the different imaging and hydrocarbon system modeling challenges posed by the complex and distinct structural styles of its hydrocarbon provinces.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece