Yurubchen Oil-Gas Field, East Siberia

Internet Geology News Letter No. 1, July 11, 1999

Can significant oil and gas have been generated a billion years ago? Can a petroleum system have developed back then, and the hydrocarbons preserved up to the present? This appears to true for the Yurubchen field in the southwest part of the Siberian craton. The area of this field (or zone) is given as 7,500 sq km in one publication (Petroleum Geology of Baykit Basin, 1997) and as 13,000 sq km in another, where it is designated as the Yurubchen-Tokhomo field. (Petroleum Geology, p. 114, 1997).

Yurubchen field is on a basement high, which is overlain by Riphean rocks of Middle Proterozoic age. This is the Kamov arch, which is structurally the highest part of the Baykit anteklize. The field has a block structure, the blocks bounded by flexures and faults. The Riphean section consists of 12 alternating clay-carbonate, carbonate, and clay units. Pays are present in the carbonates as well as in clastic-carbonates in overlying Vendian rocks of Late Proterozoic age (Petroleum Geology, p. 36, 1999). Also, a flow of gas has been recovered from weathered granite gneiss of the basement.

The reservoir rock at Yurubchen is fractured Riphean dolomite. The porosity is largely the result of leaching; the fracturing also contributes. Reservoir porosity is as high as 10 percent. Cavities are common in drill cores, and presence of caverns is indicated by drops of the drill stem and enormous absorptions of drilling mud (Petroleum Geology, p. 309, 1999).

Recoverable resources of Yurubchen-Tokhomo zone are given variously as 1.75 to 2.2 BBOE (Petroleum Geology, p. 39 and p. 268, 1999). The Russian oil company "SLAVNEFT" is shifting its exploration from West Siberia to Yurubchen area. An indication of the future importance of a region in the Newly Independent States of the Former Soviet Union is the attention it is receiving in the literature. Yurubchen certainly fits this catagory. If you wish further information on this field, please go to your library and read the articles in Petroleum Geology cited above. Yurubchen