Abstract: A Study on Lacustrine Carbonate Source Rock Evaluation System

TUO JINCAI, Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou, Gansu, Peoples Republic of China

In China, many of the off-bearing lacustrine basins are also rich in lacustrine carbonate deposits, such as Qaidam Basin and Biyang Basin. Just as marine carbonates, lacustrine carbonate deposits are mostly poor in organic matter, but strong evidences show that oils produced in many lacustrine carbonate- bearing basins are carbonate- sourced. So the lowest value of organic matter for oil generation of the lacustrine carbonate source rocks always perplexes the petroleum geologists. In this investigation, we will take thermo-pressure pyrolysis simulation to set up a evaluation system used to evaluate lacustrine carbonate source rocks. In the simulation, samples gathered from Tertiary, Qaidam Basin deposited in brackish-saline environments will be used. The samples should have different types and content of organic matter and different content of carbonate minerals. The purposes for this pyrolysis simulation are to determine the lowest value of organic matter for oil generation of the lacustrine carbonate source rocks and to research effects caused by carbonate minerals on oil-generating process and finally to set up a lacustrine carbonate source rock evaluation system. The oil-generating significance of carbonate mineral- connected organic matter such as organic matter included in lattice imperfections and crystal inclusions will also be investigated. The results of this investigation will supply an oil generation model of lacustrine carbonate source rocks and will be of great significance to nonmarine oil-gas exploration.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid