Studying and developing hydrocarbon potential of Lower-Middle-Jurassic deposits in northern areas of Western Siberia: resume and perspectives
Western-Siberian oil-gas-bearing province (WSOGP) has begun from a Lowe-Middle-Jurassic subcomplex of Jurassic system, namely from the industrial inflows in Berezovskaya (gas) and Kolpashevskaya key wells drilled down a contact zone of Jurassic and Pre-Jurassic rocks. At the north of WSOGP the Middle-Jurassic rocks have been exposed by 5200 wells in the Nadym-Pur-Taz region (NPTR), and at the territories of Yamal and Gydan peninsulas; 232 hydrocarbon fields have been discovered in the WSOGP including 112 within the Jurassic complex, including 67 Lower-Middle-Jurassic ones, including 58 in the NPTR, 8 at Yamal and 1 at Gydan. Assured Lowe-Middle-Jurassic reserves of free gas (FG) come to 611·109 m3, reserves of В2+С2 categories amount up to 1447·109 m3, correspondent reserves of oil reach 163·109 t and 151 109 t (extractable). There is no production from this subcomplex in the WSOGP. Many FG deposits are considerably underexplored due to a number of reasons; the preliminary assessed reserves exceed 70% from 2,1·1012 m3. At the northern part of WSOGP commercial significance of the Lower-Middle-Jurassic gas is much higher than significance of the same oil. Even if final factor of gas recovery equals nearly 70%, production of more than 1,3·1012 m3 of gas will be possible in with bot more than 240…250·109 t of oil (taking into account additional prospecting of hydrocarbon deposits during conversion of В2+С2 cat. reserves into the assured ones at the level of 40…50 %).The most significant FG reserves are concentrated at Bovanenkovo field at the depths of 2,5…3,1 km, as wellas in the region of Big Urengoy. Oil reserves of this subcomplex are dispersed over medium-sized and mostly small deposits (less than 3·109 t, recoverable). Considerable part of hydrocarbon reserves is associated with low-permeable reservoirs, which gave semi-industrial and not-industrial inflows during testing (e.g. Lenzitskoye oil field, etc.). Among the recently discovered “Jurassic” field the Yarudeyskoye oil-gas-condensate field is remarkable. It has big reserves of light oil and medial reserves of FG (in total 1011 t geological and 49·109 recoverable of reference fuel). According to calculations, the annual production (after 2035) from Middle-Jurassic deposits (traditional reserves) will run up to 4·1010 m3 of FG and 15·109 t of fluidal hydrocarbons.Till 2040 in the northern part of WSOGP it is destined yet to discover many dozens of hydrocarbon deposits with traditional reserves (Middle-Jurassic) and with primary alternative FG reserves( in the middle and lower horizons of Tumen suit and its analogues). After 2045, production of hydrocarbons from tight low-permeable Jurassic reservoirs (with permeability factor of 0,1…0,2 mD and less) will become wide-scale due considerable depletion of traditional Neocomian and Jurassic hydrocarbon reserves and resources.