KUALA LUMPUR, Malaysia -- As if Algeria didn’t have enough conventional gas, Sonatrach Exploration estimated the country has another 2,650 Tcf in potential shale resources.

Sonatrach has intensified its exploration efforts in order to highlight the resource potential associated with shale gas plays, said Mohamed Kaced, Sonatrach Exploration, in a presentation to the World Gas Conference 2012 on June 7 in Kuala Lumpur. The hot shale intervals, primarily in the Saharan platform, have total organic contents (TOCs) of over 10% and are in intervals more than 100 m (330 ft) thick.

“The Silurian and Frasnian hot shales have very high TOC,” Kaced said. “We have been searching for hot shales with TOCs more than 2%, thicknesses greater than 20 m (66 ft), high thermal maturity of 1.7% to 3%, and depths around 3,000 m (9,900 ft).”

In comparing the Algerian shales with US plays, Kaced stated that the shales compared favorably with the Haynesville shale and to a lesser degree with the Barnett shale.

In the first phase of the exploration, open-hole logs of shales were performed and partial cores recovered from the prospective target zones in both the Silurian and Frasnian shales. The logging and coring was done in wells that were being drilled into conventional targets in sandstone reservoirs, he noted.

The best zones for shale gas exploration are the western part of the Illizi, Ahnet-Gourara and Bechar basins.

The Ahnet-Gourara Basin has the most shale gas potential of all the basins. Both hot shales have good richness in TOC (1.5% to 5%) and thicknesses reaching as much as 160 m (528 ft). Sonatrach estimated potential resources of 0.6 to 0.8 billion cubic meters (Bcm) per sq km, he explained.

The Timimoun Basin’s potential resources are estimated at 0.36 to 0.67 Bcm/sq km.

The Ilizi Basin is prospective in the western part with good TOC (greater than 3%) and good thickness (greater than 30 m or 99 ft). In the southern part of In Amenas, the source rock contains wet gas. Both gas and liquids could be produced, Kaced said.

The Bechar Basin contains excellent source rocks with thicknesses varying from 20 m to 140 m (66 ft to 462 ft). The entire basin is in a dry gas window with organic-rich formations. One advantage is that the shales are shallow with the Frasnian at 2,000 m (6,600 ft) and the Silurian at less than 3,000 m (9,900 ft).

In a technical paper associated with the presentation, he pointed out that the Berkine Basin contained the best quality source rock on the Saharan platform. The rocks are mature, in a dry-gas phase and organic rich.

However, the formations are very deep (4,000 m to 6,000 m [13,200 ft to 19,800 ft]) with pressures ranging from 4,000 psi to 11,000 psi. These conditions are constraints to hydraulic fracturing and increase production costs, Mohamed said.

First Well, Possibly Seeking Partners

Following the completion of the evaluation phase, Sontrach is preparing to drill its first shale gas well in the second half 2012.

The estimated cost of the well, including drilling, hydraulic fracturing and completing, is US $10 million, Kaced noted. In Algeria’s gas-prone world, such a well would not be commercial, but it would give Sonatrach valuable information on the prospect.

The development of shale gas resources by a foreign company that specializes in unconventional plays might be possible, he added.

The benefits for a partner include a huge resource potential, the production of dry gas, fewer environmental constraints and large concessions.

Algeria is currently debating alterations to its petroleum law to make unconventional resource development more attractive.

The WGC paper on the “Potential of Shale Gas Plays in Algeria” was written by Mohamed Kaced and Mohamed Arab, Sonatrach Exploration, for the working committee on exploration and production.

Contact the author, Scott Weeden, at sweeden@hartenergy.com.

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