Phase Order Inversion During Heavy Oil and Bitumen Production with Solvent Addition

Abstract

Athabasca bitumen and other denser-than-water reservoir fluids are coproduced with water or are produced using water or steam injection. Organic solvent injection into reservoirs to reduce hydrocarbon resource viscosity and hence improve production rates is envisaged. A consequence of solvent addition is that the density of the resulting hydrocarbon-rich phase can drop below that of the water-rich phase over broad ranges of composition, temperature, and pressure. In this contribution, densities of Athabasca bitumen from 20 to 200 °C at 0.10, 1.12 and 3.29 MPa, Athabasca bitumen + heptane from 10 to 80 °C at 0.10 MPa and 30 to 140 °C at 0.10, 1.11, and 3.29 MPa and Athabasca bitumen + toluene from 10 to 80 °C at 0.10 MPa were measured (using an Anton Paar DMA 5000 and an Anton Paar DMA HP) and compared with those of pure and produced liquid water from 20 to 200 °C at 0.10, 1.12, and 3.29 MPa. Phase order inversion is shown to overlap with envisaged processing conditions for production, transport, and refining of denser-than-water reservoir fluids because only low mass fractions of solvent are required to cause inversion to occur. The phase order inversion envelopes also include compositions that invert twice as a function of temperature, and the upper temperature associated with phase inversion is a function of pressure. Remote from the critical point of added solvents, the phase inversion boundary is shown to be well-approximated by the ideal mixing assumption applied to Athabasca bitumen + solvent pseudobinary mixtures. The impact of solvent critical temperature on the volume of mixing for solvent + oil mixtures is discussed. Phase order inversion is a general and readily computed phenomenon.

Phase Behavior and Thermophysical Properties of Peace River Bitumen + Propane Mixtures from 303 K to 393 K

“…4 Liquid phase density values are expected to conform with values anticipated by ideal mixing at low temperatures. 4 As the critical temperature of the light hydrocarbon is approached, divergence from this behavior is expected. Systematic and significant deviation to larger negative volumes of mixing for both the L 1 (propane-rich) and the L 2 (bitumen-rich) liquid phases is anticipated on the basis of computations with equations of state such as the Peng−Robinson equation.…”

“…Bitumen remains denser than liquid water. 4 A lot of energy is used to heat the reservoir. This process has high CO 2 emissions, and the bitumen recovery is variable and low at less than 50%.…”

“…The expanding solvent-SAGD (ES-SAGD) process is one such example. 6,7 However, care must be taken to ensure that bitumen + solvent mixtures remain denser than water under production conditions, 4 and to ensure that the hydrocarbon-rich fluid remains in a single phase. Asymmetric mixtures, comprising low molar mass and high molar mass species, or where specie polarities differ significantly split into more than one liquid phase.…”

“…Upon heating, the viscosity of the bitumen decreases by orders of magnitude and it flows downward by gravity to a lower horizontal production well. Bitumen remains denser than liquid water . A lot of energy is used to heat the reservoir.…”

“…One of the ways to improve this technology is to add a low molar mass n -alkane along with less and lower pressure steam. The expanding solvent-SAGD (ES-SAGD) process is one such example. , However, care must be taken to ensure that bitumen + solvent mixtures remain denser than water under production conditions, and to ensure that the hydrocarbon-rich fluid remains in a single phase. Asymmetric mixtures, comprising low molar mass and high molar mass species, or where specie polarities differ significantly split into more than one liquid phase. , For solvent-added processes to be successful, a detailed understanding of the phase behavior of and saturated phase densities of the mixtures is required over the range of subsurface and surface facility conditions envisioned.…”