Samotlor Oil Field, West Siberia, USSR

CLARKE, JAMES W., U.S. Geological Survey, Reston, VA

The Samotlor oil field is located in the Tyumen region of the vast West Siberian Lowland of the Soviet Union. It is the largest of the more than 300 fields that have been discovered in the region as of the late 1980s. This field is typical of many of the giant fields of the world with respect to reservoir rock (sandstone), trap type (anticlinal), age of reservoir rock (Cretaceous), average depth of pay 1700-2400 m), deepest pay (2400 m), and depositional environment (shallow-water marine). The field was discovered in 1965, and production began in 1969. More than 15 billion barrels of oil have been produced, but yields are now perhaps 25% below the peak. The Samotlor field is on a structural high that is on the larger Nizhnevartov arch. Total thickness of the sedimentary section is 270 -2900 m. The reservoir rocks are within a section more than 1200 m thick. Ten pays are present, each having its own independent water-oil contact. Fine- to medium-grained deltaic sandstones and siltstones alternate with shales and also grade laterally to the west and northwest into shales. The sandstones and siltstones contain 25-60% feldspar, which is strongly altered to various clay minerals and sericite. The remainder is mostly quartz. Porosity is from 20-25%, and average permeability is 500 md.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)