FOREWORD
This report was prepared as part of the World Energy Project of the U.S. Geological Survey. For this project, the world was divided into eight regions and 937 geologic provinces, which were then ranked according to the discovered oil and gas volumes within each (Klett and others, 1997). Next, 76 "priority" provinces (exclusive of the U.S. and chosen for their high ranking) and numerous "boutique" provinces (exclusive of the U.S. and chosen for their anticipated petroleum richness or special regional economic importance) were selected for appraisal of oil and gas resources. The petroleum geology of these priority and boutique provinces is described in this series of reports. The North Sakalin Basin Province ranked 50^th in the world, exclusive of the U.S.

The purpose of the World Energy Project is to assess the quantities of oil, gas, and natural gas liquids that have the potential to be added to worldwide reserves within the next 30 years. These volumes either reside in undiscovered fields whose sizes exceed the stated minimum-field-size cutoff value for the AU (variable, but must be at least 1 million barrels of oil equivalent), or they occur as reserve growth of fields already discovered. Assessment results are documented separately from this report.

The Total Petroleum System (TPS) constitutes the basic geologic unit of the oil and gas assessment. The TPS includes all genetically related petroleum that occurs in shows and accumulations (discovered and undiscovered) that (1) has been generated by a pod or by closely related pods of mature source rock and (2) exists within a limited mappable geologic space, along with the other essential mappable geologic elements (reservoir, seal, and overburden rocks) that control the fundamental processes of generation, expulsion, migration, entrapment, and preservation of petroleum. The minimum petroleum system is that part of a TPS encompassing discovered shows and accumulations, along with the geologic space in which the various essential elements have been proved by these discoveries.

An Assessment Unit (AU) is a mappable part of a TPS in which discovered and undiscovered fields constitute a single, relatively homogenous population such that the chosen methodology of resource assessment – based on estimation of the number and sizes of undiscovered fields – is applicable. A TPS could equate to a single AU, or it can be subdivided into two or more AU if each AU is sufficiently homogeneous – in terms of geology, exploration considerations, and risk – to assess individually. AU are considered established if they contain more than 13 fields greater than the minimum established size, frontier if they contain 1-13 fields, and hypothetical if they contain no fields.

A graphical depiction of the elements of a TPSis provided in the form of an events chart that shows the times of (1) deposition of essential rock units, (2) trap formation, (3) generation, migration, and accumulation of hydrocarbons, and (4) preservation of hydrocarbons.

A numeric code identifies each region, province, TPS, and AU; these codes are uniform throughout the project and will identify the same type of entity in any of the publications. The code is as follows:

The codes for the regions and provinces are listed in Klett and others, 1997.

Oil and gas reserves quoted in this report are derived from the Petroconsultants’ Petroleum Exploration and Production database (Petroconsultants, 1996) and other reports from Petroconsultants, Inc., unless otherwise noted.

Figures in this report that show boundaries of the TPS, AU, and pods of active source rocks were compiled using geographic information system (GIS) software. Political boundaries and cartographic representations were taken, with permission, from Environmental Systems Research Institute's ArcWorld 1:3 million digital coverage (1992). They have no political significance and are displayed for general reference only. Oil and gas field centerpoints, shown on these figures, are reproduced, with permission, from Petroconsultants (1996).