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  | isbn    = 978-0-89181-379-8

  | isbn    = 978-0-89181-379-8

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Producible oil from shales or closely associated organic-lean intraformational [[lithofacies]] such as carbonates is referred to as a shale-oil resource system. Organic-rich mudstones, calcareous mudstones, or argillaceous lime mudstones are typically both the source for the petroleum and either a primary or secondary reservoir target, but optimum production can be derived from organic-lean juxtaposed carbonates, silts, or sands. Where organic-rich and organic-lean intervals are juxtaposed, the term hybrid shale-oil resource system is applied.

Producible oil from shales or closely associated organic-lean intraformational [[lithofacies]] such as carbonates is referred to as a shale-oil resource system. Organic-rich [[mudstone]]s, calcareous mudstones, or argillaceous lime mudstones are typically both the source for the petroleum and either a primary or secondary reservoir target, but optimum production can be derived from organic-lean juxtaposed carbonates, silts, or sands. Where organic-rich and organic-lean intervals are juxtaposed, the term hybrid shale-oil resource system is applied.

These systems are classified as (1) organic-rich mudstones without open fractures, (2) organic-rich mudstones with open fractures, and (3) hybrid systems that have juxtaposed, continuous organic-rich and organic-lean intervals ([[:File:M97Ch1.2FG1.jpg|Figure 1]]). For example, the Bakken Formation production is accounted for by both open-fractured shale (e.g., Bicentennial field) and hybrid shale (e.g., Elm Coulee, Sanish, and Parshall fields), where organic-rich shales are juxtaposed to organic-lean intervals, such as the Middle Member (dolomitic sand) and Three Forks (carbonate). However, [[Barnett shale play|Barnett Shale]] oil is almost always from a tight mudstone with some related matrix porosity.<ref name=EOGResources2010>EOG Resources, 2010, [http://wwgeochem.com/references/EOGMay2010Investorpresentation.pdf Investor presentation], 223 p.</ref> Monterey Shale-oil production is primarily from open-fractured shale in tectonically active areas of California. Various shale-oil resource systems are classified based on available data in Table 1. To suggest that these types are mutually exclusive is also incorrect because there can be a significant overlap in a single shale-oil resource system.

These systems are classified as (1) organic-rich mudstones without open fractures, (2) organic-rich mudstones with open fractures, and (3) hybrid systems that have juxtaposed, continuous organic-rich and organic-lean intervals ([[:File:M97Ch1.2FG1.jpg|Figure 1]]). For example, the Bakken Formation production is accounted for by both open-fractured shale (e.g., Bicentennial field) and hybrid shale (e.g., Elm Coulee, Sanish, and Parshall fields), where organic-rich shales are juxtaposed to organic-lean intervals, such as the Middle Member (dolomitic sand) and Three Forks (carbonate). However, [[Barnett shale play|Barnett Shale]] oil is almost always from a tight mudstone with some related matrix porosity.<ref name=EOGResources2010>EOG Resources, 2010, [http://wwgeochem.com/references/EOGMay2010Investorpresentation.pdf Investor presentation], 223 p.</ref> Monterey Shale-oil production is primarily from open-fractured shale in tectonically active areas of California. Various shale-oil resource systems are classified based on available data in Table 1. To suggest that these types are mutually exclusive is also incorrect because there can be a significant overlap in a single shale-oil resource system.