Morocco believes two large seismic prospects in inter-Atlas basins could bolster supplies for the proposed Maghreb-Europe gas pipeline.
Moroccan state oil company Office National de Recherches et D'Exploitations Petrolieres (Onarep) estimates combined reserves of the A-1 and A-2 prospects in the High Plateaux basin of the Atlas Mountains could amount to as much as 240 million cu m of gas equivalent. Both are near the proposed route for the pipeline, destined to ship Algerian gas through Morocco and across the Strait of Gibraltar to Spain.
As defined by about 1,000 line km of 24 fold, common depth point 2D seismic data, A-1 and A-2 primary objectives are basal Triassic clastics similar to productive reservoirs to the west in the Essaouira basin and to the east in Algeria and Lybia. Secondary objectives are upper Carboniferous clastics. At prospect A-2, Liasic carbonates could provide a third objective.
Exploration in the Moroccan portion of the Atlas Mountains is in its infancy. Only four High Plateaux wells have been drilled, none to test A-1 and A-2. However, based on results of 13 wells and 10,800 line km of 2D seismic data, Onarep pegs combined potential reserves of the High Plateaux, Guercif, Missour, and Morocco's other inter-Atlas basins at more than 1 billion cu m of gas.
Onarep considers prospects in the inter-Atlas basins comparable to Morocco's offshore prospects. But the cost of a wildcat on either High Plateaux prospect is estimated at about $6 million, or one-sixth the cost of drilling an offshore wildcat.
GEOLOGIC OVERVIEW
Onarep said prospect A-1 appears to be a 100 sq km basal Triassic sand and conglomerate structure in the southwest part of the High Plateaux basin. A-1 hydrocarbons likely are sourced from Paleozoic rock, with reservoirs sealed by thick Triassic salt. Onarep estimates A-1 potential reserves at about 95 million cu m of gas equivalent.
Prospect A-2 is similar to A-1 but appears to have additional closure in the Liasic section. Onarep estimates A-2 potential reserves at about 140 million cu m, but more seismic work is needed to better assess prospect closures.
Based on existing geophysical data, Onarep expects A-1 and A-2 net pays to exceed 50 m in thickness. However, the company bases its estimates of the prospects' potential reserves on maximum net pays of only 10 m. Depths to primary targets are estimated at 2,500 m for A-1 and 3,500 m for A-2.
Onarep's data show that High Plateaux's basal Triassic clastic intervals are made up mainly of continental red sandstone and conglomerates shed from surrounding Paleozoic formations. The Carboniferous section in High Plateaux and Missour basins is represented by 2,000-4,000 m of marine and continental sediments.
Morocco's inter-Atlas basins cover a 40,000 sq km area bounded on the south by the High Atlas Mountains, on the north by the eastern end of northern Morocco's Rif domain, on the west by the Middle Atlas Mountains, and on the east by Algeria. High Plateaux covers about 11,000 sq km within the domain, Missour 7,000 sq km, and Guercif 6,000 sq km.
Onarep has mapped High Plateaux structural traps associated with thrusting and wrench faulting, as well as stratrigraphic traps under Hercinian unconformities. There are Mesozoic section structural, stratigraphic, and paleomorphologic traps in the Triassic. Also, stratigraphic traps such as Jurassic reef carbonates have been interpreted from High Plateaux seismic data.
CASE FOR EXPLOITATION
In addition to being relative near the Maghreb-Europe pipeline route, inter-Atlas basins lie within an area of rapid economic growth in eastern Morocco served by rail, air, and roads. Industrial activity in the region includes coal mining, light manufacturing, and electrical power generation.
If inter-Atlas gas reserves prove to be half of Onarep's preliminary estimate of 1 billion cu m, Morocco likely would dedicate about half the supply to local markets and the rest to markets in Europe.
The A-1 and A-2 prospects are less than 100 miles from the proposed Maghreb-Europe pipeline route. Because of the relatively flat terrain in the area, Onarep says a gas transmission line could be laid at a reasonable cost.
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