WATER-PETROLEUM CONTACT (EN: water-oil contact; DE: Wasser-Erdol-Kontakt; FR: contact eau-huile; ES: contacto agua-petroleo; RU: водонефтяной контакт) is the surface, which separates the petroleum reservoir or the petroleum fringe of the gas (of the gas condensate) reservoir within the layer from the pressurized waters within this layer, which are contacting with these petroleum reservoirs. The boundary between the water and petroleum is not sharp; within the zone of the water-petroleum contact, there exists the transitional zone, or the zone of the mutual penetration of various thicknesses (from the fractions of the metre to 10-15 metres), which is depending on the height of the capillary rise of the water, on the collector properties of the water-bearing and petroliferous depositions, and also on the physical-chemical parameters of the water and petroleum. The morphology of the surface of the water-petroleum contact is complicated, and they consider it as the horizontal plane only conditionally. As a rule, in case of the existence of the gradient of the pressure of the waters within the layer, the water-petroleum contact is inclined in the direction of the decreasing of the pressure. The displacement of the reservoir is described using the Russell - Savchenko formula:
Hn - is the displacement of the petroleum reservoir, metres;
Rv, Rn - are the densities of the water and petroleum under the layer conditions, kilograms per cubic metre;
Dh - is the difference of the piezometric levels (the differential pressures) within the limits of the contour of the petroliferous capacity, metres.
The position of the water-petroleum contact is determined, using the testing of the boreholes, using the complex of the extracting-geophysical methods, or using the method of the calculation, according to the data from the measurements of the layer pressure of the water, petroleum, and of their densities. The position of the water-petroleum contact is counted from the mouth of the borehole, or using the absolute elevations above the level of the sea.
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