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The Petroleum Geology of Iraq

A comprehensive, up-to-date appraisal of the reservoir rocks, source rocks, seals and traps that control Iraq’s petroleum resources is reviewed by Munim Al-Rawi, an expert in the regional petroleum geology of the Middle East.
This article appeared in Vol. 10, No. 5 - 2014

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The Petroleum Geology of Iraq 

Adnan A. M. Aqrawi, Jeremy C. Goff, Andrew D. Horbury and Fadhil N. Sadooni 

Scientific Press Ltd (2010)

This book on one of the most important and prolific petroleum countries in the world reflects the varied and deep experience of the four authors and their respective organisations.

The layout and style follow the recently published books The Geology of Iraq, by Jassim and Goff (editors) 2006, and Sequence Stratigraphy of the Arabian Plate, Sharland et al., 2001. The book contents list ten chapters, references, index and authors’ biographies, but lacks a list of figures. Chapters are organised in four sections. These cover the history of oil exploration in Iraq and the region’s tectonic evolution; stratigraphic elements; petroleum systems, and a final section on future challenges in the petroleum geology of Iraq. The reliance on published material is obvious in the many referenced statements and figures.

The history of oil exploration in Iraq, presented in chapter 2, is very informative and enjoyable to read and includes a review of the work of the authors of the Stratigraphic Lexicon of Iraq, namely H.V. Dunnington, D.M. Morton and R.C. van Bellen.

The tectonics of Iraq are excellently reviewed in chapter 3, particularly the palaeostructural elements of Iraq, with very informative sections and photographs. However, the section on the tectonic evolution of Iraq is based on the evolution of the northern margin of the Gondwana and the Arabian Plate, and as a result this section is best described as theoretical. The authors themselves state on p43: “The geological history of Iraq has been strongly influenced by the events along this margin. Much of the data for interpretation of these events comes from allochthonous tectonics units whose geology is complex and poorly understood.”

The stratigraphic elements, presented in chapters 4 to 8, discuss the Precambrian and Palaeozoic, the Middle Permian to Middle Jurassic, the Middle to Upper Jurassic, and the Cretaceous and Cenozoic. The theme of the presentation is based on the sequence stratigraphic arrangement given by Sharland et al., 2001. The material is well illustrated with figures, charts, tables and superb photographs and the chapters are supplemented with excellent accounts of the petroleum system components at the end of each chapter.

A comprehensive review of petroleum systems is presented in chapter 9, and is divided into four long sections, which include an informative introduction followed by a detailed description of the components of the petroleum systems of the Palaeozoic, Jurassic, Cretaceous and oil migration and leakage in the Tertiary.

The book concludes with a chapter on the future challenges facing the petroleum geology of Iraq, including important questions on the stratigraphy and structure of Iraq, issues associated with exploration and production, and challenges related to particular stratigraphic intervals.

Two extensive lists of references are provided, which cover almost all the relevant bibliography.

Map from the back cover of ‘The Petroleum Geology of Iraq’. A Few Comments

In my view, The Petroleum Geology of Iraq is an excellent contribution to the subject. However, there are a few comments which may be helpful in future published editions of this book. 

On the history of oil exploration in Iraq, there were other very important contributors to the stratigraphy and petroleum geology of Iraq who should have been reviewed. Notably, these include the late K.M. Al-Naqib, who published major works on the Kirkuk oil field and southern Iraq; the late Prof. A. Al-Sayyab, who contributed to the stratigraphy, sedimentology and petroleum geology of Iraq in teaching, research and publications; and lastly, the late Prof. C.M.G. Bolton, who in addition to his early work in Kurdistan Iraq, published with others in 1960 the first Geologic Map of Iraq. In addition, his teaching in the Department of Geology at the University of Baghdad between 1958 and 1970 cannot be forgotten, where his foremost students became the leading oilmen in the three decades that followed the nationalisation of the oil industry in Iraq.

On the stratigraphy of Iraq in general, it is suggested that the establishment of a Country Stratigraphic Committee incorporating experts from both academia and industry would be advantageous, in order to outline guidelines for stratigraphic unit nomenclature. 

Looking at the Palaeozoic sequence stratigraphy in chapter 4, I would suggest that the illustrations from Sharland et al., 2001, could cause some confusion. For example, the charts show locally published Jordanian unit names in one place, and quote different names for the same units elsewhere. The valid Palaeozoic units names in Jordan are considered to be those used by the oil industry as advised and directed by the Petroleum Department of the Natural Resources Authority and as used by their staff in international journals, such as Keegan, et al., 1990 (which incidentally does not appear in the reference list).

In the chapter on tectonics, an important Caledonian uplift movement in western Iraq, which is reported in Numan, 1997, does not appear to be discussed in the book, or referenced. There are also some important public domain articles on the Palaeozoic and Triassic hydrocarbon potential of North West Arabia, including Iraq, known to international oil companies, which have not been used or referenced. 

But these are minor issues. The Petroleum Geology of Iraq is a well-researched, informative and detailed book, compiled by experts, which will be of great assistance to anyone interested in petroleum exploration in this important region, and I would like to congratulate the authors for this tremendous effort.

References:

Jassim, S.Z. and Goff, J.C., 2006. Geology of Iraq. Dolin, Prague and Moravan Museum, Brno (Czech Republic), pp.341.

Keegan, J. B., 1990. Palynostratigraphy of the Lower Paleozoic, Cambrian to Silurian, sediments of the Hashemite Kingdom of Jordan. Review of Palaeobotany and Palynology, 66 (1990): 66-180. Elsevier Science Publishers B.V., Amsterdam.

Numan, N.M.S., 1997. A plate tectonic scenario for the Phanerozoic succession in Iraq. Iraqi Geological Journal, v. 30, no. 2, p. 25-67.

Sharland, P.R., R. Archer, D.M. Casey, R.B. Davis, S.H. Hall, A.P. Heward, A.D. Horbury and M.D. Simmons 2001. Arabian Plate Sequence Stratigraphy. GeoArabia, Special Publication 2, Bahrain, p. 371.

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