About This Item
- Full TextFull Text(subscription required)
- Pay-Per-View PurchasePay-Per-View
Purchase Options Explain
Share This Item
The three major types of crude oil in the Williston basin--the type I oils of the Winnipeg-Red River system, the type II oils of the Bakken-Madison system, and the type III oils of the Tyler-Pennsylvanian system--can be distinguished by their sulfur isotope compositions. They have characteristic ^dgr34S values of 5.8 ± 1.2 parts per thousand (ppt), 2.8 ± 0.8 ppt, and -4.0 ± 0.7 ppt respectively. Highly mature oils have less typical values.
Type II oils which have migrated over a distance of some 150 km beyond the region of generation have maintained their characteristic ^dgr34S values even though sulfur may have been lost. This indicates little or no interaction with reservoir sulfates under normal circumstances.
On the periphery of the basin, type II oils altered by water washing and biodegradation have altered ^dgr34S values which increase from +2.9 to +9.4 ppt with the increasing degree of crude oil degradation.
The Bakken shales, source of the type II oils, have ^dgr34S distribution patterns in the reduced sulfur typical of marine sediments. The ^dgr34S values for the type II oils match most closely the ^dgr34S value of organic sulfur in the black bituminous shales of the lower Bakken.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
|Protected Document: $10|
|Internal PDF Document: $14|
|Open PDF Document: $24|
Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].