Shale Resource Systems for Oil and Gas: Part 1—Shale-gas Resource Systems

zhuhouqin

Shale resource systems have had a dramatic impact on the supply of oil and
especially gas in North America, in fact, making the United States energy
independent in natural gas reserves. These shale resource systems are typically
organic-rich mudstones that serve as both source and reservoir rock or source
petroleum found in juxtaposed organic-lean facies. Success in producing gas and
oil from these typically ultra-low-permeability (nanodarcys) and low-porosity
(<15%) reservoirs has resulted in a worldwide exploration effort to locate and produce
these resource systems. Successful development of shale-gas resource systems
can potentially provide a long-term energy supply in the United States with the
cleanest and lowest carbon dioxide-emitting carbon-based energy source.
Shale-gas resource systems vary considerably system to system, yet do share
some commonalities with the best systems, which are, to date, marine shales with
good to excellent total organic carbon (TOC) values, gas window thermal maturity,
mixed organic-rich and organic-lean lithofacies, and brittle rock fabric. A
general classification scheme for these systems includes gas type, organic richness,
thermal maturity, and juxtaposition of organic-lean, nonclay lithofacies. Such
a classification scheme is very basic, having four continuous shale-gas resource
types: (1) biogenic systems, (2) organic-rich mudstone systems at low thermal
maturity, (3) organic-rich mudstone systems at a high thermal maturity, and (4)
hybrid systems that contain juxtaposed source and nonsource intervals.
Three types of porosity generally exist in these systems: matrix porosity,
organic porosity derived from decomposition of organic matter, and fracture porosity.
However, fracture porosity has not proven to be an important storage
mechanism in thermogenic shale-gas resource systems.
To predict accurately the actual resource potential, the determination of original
hydrogen and organic carbon contents is necessary. This has been a cumbersome
task that is simplified by the use of a graphic routine and frequency distribution
(P50) hydrogen index in the absence of immature source rocks or data sets.

zhyq1013

好资料！！！