Properties Of Peace River Bitumen Saturated With Field Gas Mixtures

Abstract

Abstract This paper presents new data for the viscosity and gas solubility of Peace River bitumen saturated with CO2 and two field gases. The Peace River Produced Gas was rich in carbon dioxide while the Three Creeks Gas was rich in methane. The experimental results show that the field gas-saturated bitumen properties are between those of bitumen saturated with pure carbon dioxide and methane. These tests were performed on a new experimental apparatus for measuring the properties of gas-saturated bitumens. In addition to providing data on the viscosity and gas-solubility of bitumen, the apparatus is capable oj detecting the presence of solid (asphaltene) particles. Another unique feature of the experimental procedure allows for continuous sampling of released gas as the pressure is lowered. With each of the three gases, experiments were performed at four temperatures ranging from 15 ºC to 120 ºC and pressures up to 10 MPa. In experiments with field gas mixtures composition of the released gas showed a considerable variation with system pressure. The CO2 content in the released gas was found to gradually increase as the system pressure was reduced to atmospheric pressure. For methane and other light gases the trends were quite different. Introduction Reserves of conventional crude oils in Alberta have been for some time declining. However, Alberta has the world's largest known deposits, 200 billion m3, of bituminous oil sands(1). Additionally, there are significant deposits of heavy oil, natural gas and coal. The major obstacle to the economic recovery and processing of heavy oils and bitumens is their high viscosity. To facilitate the recovery of these heavy oils and bitumens a Viscosity reduction process – such as gas-miscible or gas immiscible flood, steam stimulation, or in situ combustion – is necessary. In addition, adequate process equipment design requires a knowledge of the viscosity of heavy hydrocarbon/gas systems. The viscosity data for the following gas-free Alberta bitumens have been provided in the past: Athabasca (GCOS) bitumen(2–5), Athabasca (ARC) bitumen from ARC Sample Bank(6), Peace River bitumen from a core sample(7), Peace River bitumen from PRISP facility(8), Marguerite Lake bitumen(9), Wabasca bitumen(10), and Cold Lake bitumen(11). Figure 1 shows the effect of temperature on the viscosity of gas-free Alberta bitumens. It is obvious that the bitumens from Athabasca and Peace River regions have high viscosities, from Marguerite Lake and Cold Lake regions have intermediate viscosities, and a sample of Wabasca bitumen is far less viscous. Table 1 presents a simple bulk analysis for the Alberta bitumens. Detailed analyses of Alberta bitumens are presented in the AOSTRA Data Book(12). The data in Table 1 and Figure 1 indicate that bitumen viscosity increases generally with an increase in the asphaltene content and the average molecular weight of the bitumen. The viscosity, density and gas-solubility data reported by the authors for several bitumen-gas systems are summarized in Table 2. Also shown in Table 2 are reference numbers to published papers in which the data appear. In general, the order of decreasing solubility of gases in bitumens is C2H6. CO2, CH4, CO and N2.