Transcript for Wrestling with Uncertainty, segment 09 of 16


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{{{The Geologic Play}}}

The play's the thing.

Shakespeare probably knew little or nothing about oil and gas, but in that line he may well have been speaking of the National Resource Assessment. In the assessment the play is the thing, the focus of effort, but here it's a geologic play, a concept that enables us to organize the vast array of information that comes from three million wells in eight regions across the United States.

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A petroleum play is a group of accumulations with similar hydrocarbon sources, reservoirs, and traps. A play might include all the accumulations associated with salt structures in an area or all those related with geologic faults or anticlines. By connecting individual wells with a specific set of geological conditions the, idea lets us develop historical trends for each play.

In order to identify plays in the province, the province geologist begins by giving all of the available information concerning petroleum geology of this place. He or she talks to state geologists, talks to oil company exploration people, talks to academics, and then defines plays based on the principal geologic attributes of source rock, reservoir rock, and trap. In many cases these attributes are even evident in map view. For example, here in the powder of a basin you can see the boundaries of the sand dunes that constitute the reservoirs for the minnalusa. You can see the great channel sandstones, the muddy sandstones. You can see oil accumulations that have been explored for here in the basin margin anticlines. These geologic characteristics then are used to draw a boundary. This is a geologic boundary. For example, here is the boundary of a muddy sandstone play, and these boundaries will be set, for example, by limits of potential reservoirs on outcrop or by down-dip pinchouts for the sandstones that constitute the reservoir. This geologic boundary is really based on these attributes, and this constitutes the fundamental unit of the play that we assess.