Structure and Petroleum Potential of a Unique Yurubcheno Field from the Standpoint of System-Lithmological (Sequence Stratigraphic) Analysis of the Pre-Cambrian Sediments, Kransnoyarsk Province, Russia

V. A. Krinin, O. V. Gutina, A. V. Panteleyev, A. L. Proskuryakov

The Yurubcheno gas-condensate-oil field is the largest of several major oil and gas accumulations discovered in the Pre-Cambrian (Riphean) section of the Krasnoyarsk Province. The field is located over the crest of the Kamov arch of the Baykit anticline. The transgressive-regressive cyclites (sequences) have been analyzed using the system-lithmological technique developed by Yu. N. Karagodin.

Initial transgressive portions of the Riphean cyclites are composed of coarse-grained clastic dolomites and sandstones 10 to 70 meters thick. Late transgressive cyclites include organic-rich (phytogenic) dolomites, shaly dolomites and argillites with fine "chemical" structure. Regressive portions of the cyclites are composed of nolular silicified organic dolomites which are non-uniformly cavernous and fractured. These regressive facies range from 200 to 500 meters in thickness. The Riphean section is overlain by Sinian (Vendian) to Cambrian clastic carbonaceous and sulphate-carbonaceous rocks.

The Yurubcheno field is associated with cavernous and fractured dolomites from which light, low sulphur crude is produced. In wells at the nearby Madrin prospect, three independent reservoirs occur within separate regressive cyclites. The reservoir in each is cavernous dolomite associated with erosional unconformities at the top of each cyclite. Top-seal for each of the reservoir intervals is provided by shales of the transgressive phase of the overlying cyclite. These relationships may open the opportunity of exploring for independent inter-Riphean accumulations.

The discovery of commercial oil accumulation in the Riphean of the Baykit anticline drew attention to the same complex developed over the Katanga oil-gas region. Presently, high quality reservoirs have been discovered there within the Riphean. This suggests that the Riphean may be prospective over the vast areas of several regions.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995