The Flow of North Slope Crude Oil and Its Emulsions at Low Temperatures

This paper describes work that was carried out to determine the nature of low temperature flow through pipes of Prudhoe Bay crude oil and its emulsions with synthetic brine. These fluids were prepared and pumped both at temperatures ranging from 10 degrees to 30 degrees F and also at room temperature through a flow system consisting of a reservoir, a pump, a copper tube heat exchanger, a tubular flow resistance, and a return line to the reservoir. The heat exchanger and the flow resistance were immersed in a constant temperature bath (water and methanol) that could be adjusted to various temperatures. The pressure drop across the resistance and the viscosity of the fluids were observed and recorded. The variation of viscosity with temperature and with emulsion quality (ratio of oil volume to total volume) was studied. A significant lowering of the apparent viscosity and of the pressure drop through the flow resistance was pressure drop through the flow resistance was found using emulsions as compared to the crude oil. Pumping an oil-in-water emulsion ma significant advantages in a Trans-Alaskan pipeline. pipeline Introduction The flow of emulsions in pipelines has received little attention in the petroleum industry. In particular, no work appears to have been done on the subject of emulsions flowing at low temperatures. Nevertheless, the subject may have considerable impact on the industry in light of the recent discoveries of very large oil deposits on the North Slope of Alaska. An emulsion has been defined as "….. a heterogeneous system consisting of at least one immiscible liquid intimately dispersed in another in the form of droplets." An emulsion has two phases, the continuous and the dispersed. An phases, the continuous and the dispersed. An oil-in-water emulsion (O/W) has water as the continuous phase and a water-in-oil emulsion (W/O) has oil as the continuous phase. The experiments described in this paper deal with both types although the primary emphasis was on the oil-in-water emulsions. Most studies of the rheology of emulsions have been done at or above room temperature. The only actual work done at low temperatures was concerned with the effect on the stability of emulsions through a freezing and then a thawing process. The effects of various parameters on the viscosity of emulsions have been studied extensively, although not at low temperatures.