«Oilfield engineering»

Forecast of producing wells initial water-flooding in poorly saturated oil reservoirs in the Western Siberia fields

UDC: 622.276
DOI: 10.33285/0207-2351-2022-2(638)-10-18

Authors:

¹ PB "TERM", Tyumen, Russia

Keywords: oil fields, Khanty-Mansy Autonomous territiry – Yugra, Yamalo-Nenets Autonomous territory, weakly saturated oil reservoir, well, hydraulic fracturing, initial water cut, "fact-forecast" comparison

Annotation:

Comparison of parameters’ "free" samples in the fields during the first stage of the subsoil assets development of the Middle Ob region (35 layers that were put into operation before 1978) and the Noyabrsk region (14 layers that were put into operation in the 1980s) proved their practical coincidence in terms of the average oil saturation coefficient (Knn – 0,63 and 0,63); there was some difference in porosity – 22 and 19 %; the discrepancy in permeability is large – 280 and 50 mD, respectively. In the Yugansk region of the Middle Ob region, the average actual initial water cut for 8 thousand new wells commissioned in 1966–1985 was 10 %. In the Noyabrsk region, for 4010 wells commissioned in 1990–1997, the water cut was 2 times higher (20 %). The average approved oil recovery factor for Yuganskneftegaz during this period made 0,37, and for the Noyabrskoye fields – 0,35, that is, the difference in oil recovery was small. The value of the "critical" oil saturation, below which water appears in the wells production, depends on the reservoirs permeability. In the fields of the Middle Ob region the "critical" oil saturation of low-permeable reservoirs (< 50 mD) made approximately 50...55 %. For the YuV11 reservoir of the Orekhovsky site of the Orekhovo-Ermakovskoye field, a stable linear dependence of the initial (for the first 3 months) water cut in the wells subjected to hydraulic fracturing on oil saturation (in the range of 35...50 %) was obtained. Hydraulic fracturing strongly affects the initial water cut. The analysis of the obtained dependence allows making the assumption that hydraulic fracturing in the sites of a purely oil zone (Knn = 50 %), due to the breakthrough of clay bridges, increases the inlet water cut of the treated wells by about 25...30 % abs. The applicability of the proposed formula for assessing the initial water cut for other reservoirs (in particular, reservoirs of the AB1 group) of the neighboring oil region at the fields of the LLC "LUKOIL–Western Siberia" has been established.

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