Page 27 - Fundamentals of Gas Shale Reservoirs

GLOBAL RESOURCE DATA 7
The estimation methodology involved applying knowledge production, the Sichuan Basin has a well‐developed network
about US gas shales to other shales in different regions. In of natural gas pipelines, in addition to proximity to large
simple terms, this involved assuming that all prospective cities with considerable energy demand. That said, the pro­
shales contain 17.7 Tcf of gas for every Gt (gigatonne) of spective areas do suffer from remoteness and often a lack of
shale in‐place. The value presented by Rogner is a GIP water (UPI, 2013).
estimate, which does not conform to the definition of TRR
used by the EIA and defined by Dong et al. (2013). 1.5.2 The United States
The Rogner GIP estimates were converted to TRR values
by averaging the GIP:TRR ratios for global shale gas plays The United States has numerous producing shale gas
from other sources, then applying this average ratio to the basins, many of which are very well understood due to pro­
Rogner GIP values. It was also necessary to adjust Rogner duction‐related data. It also has the second largest TRR
Middle East values to account for overlap with EIA sources. within this study.
A total of 16 basins comprising 20 shale gas plays
are noted within the source study, with a cumulative TRR
1.5 GLOBAL RESOURCE DATA of 751 Tcf. All the prospective shales are of marine origin,
with the majority associated with foreland basins (e.g.,
The shale gas resource data is presented in Appendix A.1. Appalachian Basin) and Devonian deposition. The majority
The information is presented as a hierarchy in terms of are of favorable depth, with some as shallow as 3000 ft,
region, country, basin, and shale play. A summary of each although the national average is approximately 7500 ft. This
prospective country, and in some cases region, is presented shallow depth combined with competitive drilling costs
further. This chapter is limited to the general geological often equates to relatively low cost production. Organic
reservoir characteristics and a brief summary of the status of content is generally very favorable, with an extremely high
exploration or production. average of some 6–7%, with some shale gas plays (i.e.,
All quantitative reservoir properties and characteristics Marcellus Shale) reporting average TOC of 12%. The United
(i.e., TOC, depth, and thickness) are indicative nonweighted States also has considerable local experience in the drilling
averages only, will vary greatly across any one play, and are and hydraulic fracturing service industry.
not representative of the likelihood of commercial shale gas EIA sources (2011a) have considerable information on
production. However, they do give an indication of the each US shale gas play; as such, no further information is
potential resource quality. provided here.
All information has been sourced from the EIA documen­
tation (2011a, b, c), except where stated otherwise.
1.5.3 Mexico
Mexico has the third largest TRR within this review, at
1.5.1 China
approximately 681 Tcf. The shales are of marine origin
China has two major prospective basins, the Sichuan and were deposited in rift basins during Jurassic and
Basin and the Tarim Basin, with a combined estimated TRR Cretaceous. The shale plays are favorable in terms of thick­
of 1275 Tcf. This is the largest TRR of any single nation ness (200–400 ft), low clay content, organic richness (3–5%
within this review and supports the opinion that China is average), and gas mature. However, the majority of resources
widely regarded as having excellent potential for shale gas occur quite deep at between 10,000 and 12,000 ft.
development. Mexico’s most prospective resources, within the Eagle
The four target shales within both basins were deposited Ford Shale, are time comparable to those in the SE
on a passive margin in a marine environment from Cambrian USA. However, Mexico’s coastal shale zone is narrower,
to Silurian times. They are thick (200–400 ft), dry gas mature less continuous, and structurally much more complex than
(Ro of 2.0–2.5), and have moderate clay content. However, the equivalent in the United States (EIA, 2011b).
the shales are situated relatively deep at depths of 10,000– However, due to the similarities, there is the potential for
14,000 ft, and have only moderate organic content (2–3%). similar success.
Geological complexity is high in certain parts of both basins, There has only been very limited exploration activity in
which is the reason why large parts of the basin have Mexico, with no wells as of 2011.
currently been disregarded in preparing TRR estimates
(EIA, 2011b). 1.5.4 Southern South America
There is considerable exploration activity in China due
to the potential significance in terms of domestic energy Southern South America is considered as one “zone” in this
supply, less reliance on the Middle East, and high domestic section because the key basins are very large and span many
demand for energy. Although there is currently no shale gas borders.