Tight-Gas Exploration in Saudi Arabia
Saudi Arabia, long known for its enormous structures, very high rate and relatively shallow wells is continuing its extensive conventional exploration activity. However, it is also starting down the path of looking at “unconventional” resources, especially tight gas reservoirs. Given Saudi Arabia's enormous conventional hydrocarbon reserves, what's driving this interest?
There are two primary drivers:
1) Identifying the Kingdom's ultimate resource potential; and
2) Determination of domestic gas supply potential.
The primary focus of the search for “unconventional” resources is the lower Paleozoic siliciclastic succession. This succession is dominantly a pile of sandstones several thousand feet thick. In the middle of which is the Silurian aged Qusaiba Shale. This is the source rock for most of Saudi Arabia's Paleozoic hydrocarbons. The nature of the Lower Paleozoic succession varies considerably across Saudi Arabia from outcrop to 20,000'+ depths and with reservoir qualities that range from conventional to distinctly tight.
The focus of this paper is the tight gas sandstones, that is, sandstones which do not flow at commercial rates using Saudi Aramco's standard drilling, completion and stimulation procedures. Typically these sandstones have <12% porosity and <1mD permeability. However, this is not a definitive definition.
In Saudi Arabia, the Lower Paleozoic succession below the currently producing conventional reservoirs is poorly understood and is only now being seriously investigated. Exploration activity in Saudi Arabia over the past 3 years has more than doubled the number of lower Paleozoic penetrations in southern Saudi Arabia.
This activity has resulted in a number of key developments:
1) Increased understanding of the Lower Paleozoic succession, especially the Sarah (earliest Silurian), which has allowed extensive re-interpretation of the paleogeography of this formation in the southern Saudi Arabia;
2) Identification of entirely new play types in Saudi Arabia; and
3) Confirmation that the pre-Qusaiba sandstones of the Sarah & Qasim (Late Ordovician) contain significant untapped hydrocarbon resources.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009