Читать книгу Reservoir Characterization - Группа авторов - Страница 58

Carbonate rocks contain major oil and gas deposits throughout the world. They commonly have been discounted as important source rock due to lower organic-carbon content, however, carbonate source rocks contain mostly sapropelic (oil-prone, Type II)) organic matter capable of generating significant quantities of oil.

The objective of the study was to provide an overview of the geochemical characteristics of carbonate-derived oils collected from different wells and fields. A total of 6 Cretaceous carbonate core samples and 14 oils from Tertiary (5) and Cretaceous (9) reservoirs were investigated using advanced geochemical technologies.

Almost all Tertiary oils in this study are severely biodegraded whereas, the Cretaceous oils are not.

All the oils studied show biomarker parameters that are characteristic of oils derived from carbonate source rocks, such as:

 Pristane/phytane ratios below 1

 High C29/C30-hopane ratios

 Low steranes/hopanes ratios

 High C35-homohopane index values

 High dibenzothiophene/phenanthrene ratio