An Innovative Way To Produce and Transport Heavy Oil Through Dispersion in Water: Laboratory Study and Field Test Results

Abstract

Abstract A patented innovative system to produce and transport heavy and very viscous oils was developed in the laboratory and tested in the field. Results show a remarkable improvement comparing this system to the traditional ones based on the injection of a hydrocarbon diluent or of a surfactant solution to produce an oil-in-water emulsion. The system is based on the injection of a water stream, to which a dispersing agent has been added, into the well without any modification of the existing completion. Field tests show that, as soon as the water solution comes into contact with the crude, an oil in water dispersion (70/30 oil-water ratio) is created with a viscosity 30-50 times lower than the viscosity of the diluted crude. A fourfold increase in oil production was also achieved compared to normal production with the injection of diluent. The produced dispersion was pumped to the oil collection centre, 1 Km from the well, showing a decrease of friction losses along the pipe of six times that of the diluted crude. Temperature variation down to 5 C does not affect viscosity while the diluted crude viscosity shows an increase by a factor of ten compared to the viscosity at normal ambient temperature (20-25 C). Separation of the dispersion depends on the dispersing agent concentration and on the degree of mixing of the dispersion itself. Gravity separation produces a crude oil with a 68% water-cut. This was achieved without the addition of any demulsifier and using the same settling time normally used in the field facilities to separate the water-diluted crude mixtures. The residual water can then be separated with a traditional electrostatic separator. Introduction The volume of original heavy oil in place in Italian reservoirs discovered and operated by AGIP is estimated to be about 3800 x106 STB. These reservoirs are present mainly in Sicily and in the centre-south Adriatic Sea. The fields currently being developed normally have high production costs, mainly due to the use of a diluent (diesel) which is added in the well in order to reduce the density and, more importantly, the viscosity of the crude. These costs, added to the low commercial value of the crude, have up to now hindered the development of most Italian offshore reservoirs. It was therefore necessary to identify artificial lifting and transport technologies which were more economical than the use of a hydrocarbon diluent. Literature reports numerous methods in which the diluent is replaced with a water solution of a surfactant suitable for inducing the formation of an oil-in-water emulsion. P. 283^