Dr Moujahed al-Husseini has been Editor-in-Chief of GeoArabia, the journal of Middle East Petroleum Geosciences, since 1995. He was Saudi Aramco's Exploration Manager between 1989-92 when eight Paleozoic oil and gas fields were discovered in central and northwest Saudi Arabia, and one in the Red Sea. Dr Sadad al-Husseini, formerly Saudi Aramco's Executive Vice President for Exploration and Producing and a Member of its Board of Directors, retired from the company on 1 March 2004.
On 18 April 2007, the US energy consultancy IHS issued a press release stating that up to 100bn barrels of oil resources remained to be discovered in the Western Desert of Iraq (www.ihs.com). The following day this release was quoted on the front-page of London's Financial Times and the following week in many other newspapers and magazines (for example: Dubai's Gulf News, 23 April; Time Magazine, 24 April; and MEES, 30 April).
This conclusion stands in stark contrast to the 2004 study by the US Geological Survey (USGS) and GeoDesign (a consultancy that specializes in Iraq's petroleum geology) that estimated the undiscovered oil resources of Iraq's Western Desert to total only 0.5bn barrels at the 95% level of probability, and 1.6bn barrels at the 50% level of probability (Verma, Ahlbrandt and Al-Gailani, 2004).
The USGS-Geodesign study used a modern geological-statistical basin model that combined all the then-available data and knowledge regarding the petroleum reservoirs, source rocks, migration routes and structural traps of Iraq. It considered 526 known prospects and fields, of which 370 remained undrilled, to estimate the potential number and sizes of undiscovered fields. The IHS press release stated that its own study had evaluated a comparable number of 516 known structures, of which 435 were undrilled prospects or non-commercial discoveries.
The USGS-Geodesign study concluded that the undiscovered crude oil resources of all of Iraq, including the Western Desert, may only total 13.2bn barrels at the 95% level of probability, and 45.1bn barrels at the 50% level of probability. They did not consider Iraq's undiscovered resources to exceed 84.1bn barrels even at the 5% level of probability. These total estimates fall far short of the IHS conclusions for just the Western Desert of Iraq.
This discrepancy is paradoxical because the potential petroleum resources of Iraq's Western Desert are relatively easy to estimate. For example, it is well-established from existing wells and seismic data in this and adjoining regions that the prospective formations in western Iraq are mostly of Paleozoic age and characterized by complex geology (Al-Hadidy, 2007). This is confirmed by the reservoirs in Akkas field, the only commercial oil and gas/condensate field in the Western Desert of Iraq.
The analog to the Akkas field is Jordan's Paleozoic Risha field located along the Iraqi-Jordanian border. Risha field produces 30mn cfd from more than 30 wells. It extends across a vast area (10km by 50km) but the reservoir is a thin sheet of complex sandstones in faulted glacio-fluvial channels, ranging in thickness from 2ms to 12ms. Its proven reserves are 180bn cu ft of gas, the equivalent of only 32.4mn barrels of oil.
Besides Jordan and Iraq, this Paleozoic petroleum system has also been evaluated in eastern Syria and northwest Saudi Arabia by both seismic and wildcat drilling activities. These efforts resulted in unsuccessful exploratory wells in many large structures, and the discovery of one small gas field near Tabuk in Saudi Arabia.
Based on these results, the indications are clear that this vast region (extending from northwest Saudi Arabia through eastern Jordan and Syria, and western Iraq) is not very prospective for oil. In fact to discover 100bn barrels of crude oil in the Western Desert of Iraq, as suggested by the IHS report, would require discovering and delineating the equivalent of 3,000 Risha-sized oilfields. Clearly if this was a realistic possibility, many such prospects would have been discovered and drilled decades ago when intensive exploration became widespread across the entire Middle East region.
Perhaps the most important conclusion to be drawn from these profoundly contradictory studies is the need for a higher level of discipline and objectivity in the process of estimating global oil resources. After all, the difference between the two studies, in just one region, of nearly 100bn barrels of oil resources represents nearly 10% of the proven oil reserves of the world. While identical conclusions from such studies are not realistic, discrepancies that differ by two orders of magnitude must surely indicate a major flaw in the resource estimation process.
By Moujahed Al-Husseini and Sadad Al-Husseini
© MEES 2007
