Page 28 - Fundamentals of Gas Shale Reservoirs

8 GAS SHALE: GLOBAL SIGNIFICANCE, DISTRIBUTION, AND CHALLENGES

Of particular interest are the Parana‐Chaco Basin are of marine origin, with the exception of the Cooper
(Paraguay, Brazil, Argentina, Bolovia) and the Neuquen Basin Permian shale that was deposited in a lacustrine
Basin (Argentina), since they are associated with the majority environment.
of the 1195 Tcf TRR associated with this region. All shales The shallowest resources are within the Cooper Basin, at
within these two basins are of marine origin, and were approximately 8,000 ft, with the other shales being at depths
deposited in a rift and back‐arc basin, respectively. of between 10,000 ft (Perth Basin) and 12,000 ft (Canning
The Parana‐Chaco Basin shales are at a relatively shallow Basin). All the shales have favorable characteristics, such as
depth (7500 ft), are extremely thick (1000 ft), have low clay low clay content, thermal maturity, normal to overpressured,
content, and have moderate TOC (2.5%). However, they are and high average TOC (>2.5%, typically around 3.5%).
relatively low in terms of maturity (0.9% Ro). Active exploration is underway within Australia, particu­
The Neuquen Basin has two prospective shales, at depths larly within the Cooper Basin (Beach Petroleum) and the
of 8,000 and 12,000 ft. They are generally more mature, have Canning Basin (Buru Energy). Although there is active gas
higher TOC, and are more overpressured than the Parana‐ production from conventional sources within the Cooper
Chaco Basin. Basin, the shale is of the less favorable lacustrine origin, and
There is also a sizeable TRR in the Austral‐Magnallanes there are reported higher CO concentrations. The conditions
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Basin on the border between Argentina and Chile, which has within the Canning Basin seem more favorable, although the
similar characteristics to the Parana‐Chaco Basin shales, but industry has to compete with high‐domestic gas production
with lower estimated TOC and higher clay content. from other conventional gas sources, relatively high produc­
Active exploration is underway within the Neuquen tion and labor costs, and a currently high Australian dollar.
Basin in Argentina. Argentina also has existing gas infra­
structure and favorable policy to support unconventional 1.5.7 Canada
gas production.
Canada has approximately 388 Tcf of shale gas (TRR), the
majority of which is within five subbasins within the vast
1.5.5 South Africa
Western Canadian Basin (WCB). The WCB is a modern
South Africa has approximately 485 Tcf of shale gas (TRR) foreland basin associated with the Rocky Mountains,
within the vast Karoo Basin, which extends across nearly although the prospective shales were deposited in a passive
two‐thirds of the country. There are three prospective shales margin marine environment. Gas shale depths and thick­
within this basin, all of which were deposited during the nesses are relatively favorable, with the majority of resources
Permian in a marine environment associated with a foreland at approximately 8000 ft, and with typical thickness of bet­
basin. The shales are relatively thick (ca. 100–150 ft), shal­ ween 200 and 400 ft. The organic content is also generally
low (8000 ft), low in clay content, highly organic rich (6% good (>3.5%), clay content is low, thermal maturity is high,
within the Whitehill Formation), mature, and overpressured. and the shales are often slightly overpressured.
However, one notable downside is the presence of The majority of WCB subbasins are very favorable for
intruded volcanics (sills), which may impact on resource development due to proximity to significant conventional
quality, limit the use of seismic, increase the risk of explora­ gas pipeline infrastructure. Exploration has been active for
tion, and elevate the CO content. There is also no significant many years, with significant development phase work being
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gas pipeline infrastructure within the Karoo basin, with undertaken. However, commercial scale production has not
existing gas supplies coming from Mozambique to the North. yet commenced.
Exploration activity is increasing in the region, with multi­ There are some smaller prospective shale formations on
nationals (i.e., Shell) holding large permits, and with drilling the east coast, with the Appalachian Basin being the most
expected to commence sometime during 2015. However, significant and favorable, although the resource quality is
there were wells drilled pre‐1970, which indicated gas satura­ less than west coast equivalents, with lower TOC (2%).
tion and potential for flow through existing fractures. However, there is also existing conventional gas infrastruc­
ture and some active exploration, hence good potential for
the development of favorable areas. It also has proximity to
1.5.6 Australia
US shale gas basins, which have good industry capability.
Four prospective basins have been identified within
Australia—the Cooper Basin in central Australia, the 1.5.8 North Africa
Maryborough Basin in Queensland, and the Perth and
Canning Basins in Western Australia. The combined TRR North Africa has a considerable shale gas TRR of approxi­
for these basins is approximately 396 Tcf. mately 557 Tcf, with the majority being within Libya
Each of the basins have quite different characteristics in (290 Tcf) and Algeria (230 Tcf). There are two key basins:
terms of basin type and age, but all of the associated shales the Ghadames Basin (mainly Algerian) and the Sirt Basin