Anomalously viscous oils

ANOMALOUSLY VISCOUS OILS (EN: non-Newtonian viscous oils; DE: Erdol mit Viskositatsanomalie; FR: petrole de viscosite anomale; ES: petroleo de viscosidad anomale. RU: аномально вязкие нефти) are the oils, which are not obeying the Newton's law of the viscous friction during their flow (for example, the non-Newtonian oils). They are characterized by the anomaly of viscosity in case of the small shear stresses, and also by the violation of the Darcy's law during the filtration within the porous media (the mobility of the oil in case of the small gradients of pressure is very low). The anomalies of viscosity are conditioned by the appearance within the anomalously viscous oils of the spatial structure, which is formed by the aggregates of the macromolecular paraffinic hydrocarbons in case of decreasing of the reservoir temperature below the temperature of saturation of the oil with paraffin or asphaltenes. The strength of such aggregates depends on the composition of oil and gas, which is dissolved within it, on the temperature, on the pressure, and also on the shear stresses, which are being created. The content of asphaltenes within the reservoir oil usually increases within the zones of reservoir, which are adjacent to the water-oil contact, the anomalies of the viscosity of oil are amplified correspondingly.

The development of reservoirs of anomalously viscous oil is complicated by the formation of the stagnation zones; the oil recovery ratio in case of the traditional methods of development is low; the displacement of the oil by water leads to the rapid watering of the extracting drilled wells. The increase of the oil recovery ratio of reservoirs of anomalously viscous oil is achieved by the thermal impact onto reservoir by the way of injection of solvents, carbon dioxide, polymer solutions, by the creation of the increased gradients of pressure, by the alignment of the profiles of receptivity. For the shallowly embedded reservoirs, there may be used the open pit, underground mine, and mine-borehole methods of development. For the transportation of anomalously viscous oil through pipelines, they heat it at the pumping stations, and introduce the dispersants of paraffin into it. The known fields of anomalously viscous oil: within the USSR are the Arlan, Uzen, Karajanbas, Zhetybai, Kushkulei; abroad are the Cold Lake, Lloydminster (Canada); Kernriver, Santa Maria Valley (USA); Hobo, Morichal (Venezuela); and others.