Formation And Distribution Of Giant Oil And Gas Fields In The Northern West Siberian Basin

Siberian West petroliferous Basin is the one largest and richest of oil and gas in Russia, and the highest in gas production rates, it is also one of the biggest petroleum basins from 1970s. This paper is mainly based on the Petroleum Geology and Petroleum Resources Assessment, studied regional geologic configuration and petroleum geologic characteristics of Siberia Basin, and analyzed the formation and distribution of giant oil and gas fields in the basin.In this paper, based on the data of 105 giant oil and gas fields, combining the tectonic-sedimentary evolution of basin and applying the research clue and method, closely analyzes the elements of play of basin including the source rocks, reservoirs and seals and so forth. Through dissecting the typical large oil and gas accumulations, it is concluded that giant oil fields mainly lie in the southern basin and giant gas fields chiefly locate in the northern basin.In this paper, it can conclude that hydrocarbon generation of Siberia Basin has several characteristics:(1)The giant gas fields mainly locate in the Nadym-Taz and South Kara-Yamal fileds province in the northern basin,the reservoirs of the Urengoy field, Yamburg field, Medvezh field and other gas fields in the northern basin locate in the Upper Cretaceous, which Cennomanian Stage is the main gas reservoirs.The mudstone of turonian which is up to these reservoir is the mainly cap rock around this area.(2)The gaint oil field mainly locate on the central of Siberia Basin,Particularly, the Middle Ob Petroliferous Province is the most important region, which contains 59.1% petroleum and condensate oil reserves of basin, the marine mudstone which is Bazhenovformation deposited in late Jurassic is the key surce rock , Pokur formation acts as the mainly reservoir.(3)The Bazhenov formation of Upper Jurassic and its equal formations are the most important source rocks, which their TOC is over 7%. The sandstones of Cennomanian Stage in the top of Cretaceous System are the main reservoir of most giant oil and gas fields which the average thickness can reach to 800m. This basin developed many complicate structural-stratigraphic traps, and the large oil and gas accumulations are mainly structural traps, which means there are widely distributed plays of hydrocarbon accumulation associated with large scale uplifts including placanticlines, domes and so on.(4)The main exploration targets of prospect increasing oil reserves are still the Neocomian Series and Jurassic System of Middle Ob Petroliferous Province and Nadym-Taz Petroliferous Province. However, the increasing gas reserves still depend on the Nadym-Taz Petroliferous Province and Kara-Yamal Petroliferous Province.