A Systematic Workflow Process for Heavy Oil Characterization: Experimental Techniques and Challenges

Abstract

Heavy crude oil reserves are steadily gaining attention as the world's energy demand increases. The fluid characterization of heavy oil and bitumen is critical in deciding best extraction, production, and processing methods of a heavy oil asset. High viscosity, low API, low saturation pressure, and low GOR impose challenges in measuring fluid properties of heavy oil. Such challenges include fluid sampling, sample handling, cleaning and de-emulsification of heavy samples and slow evolution of gas from oil phase during pressure-volume-temperature (PVT) testing-e.g., constant composition expansion (CCE) experiment. Due to these challenges, the accurate and reliable fluid characterization of heavy oil becomes more difficult. Currently, no industry standards exist for heavy oil property measurements. More often, heavy oil property measurements are performed in the same way as black oil fluid property measurements. This poses a big risk in obtaining erroneous fluid properties measurement for heavy oils. This paper summarizes the heavy oil fluid characterization technique that includes fluid sample handling, PVT analysis, fluid viscosity, emulsion and rheology, slow kinetics of gas evolution during CCE experiment, solvent solubility study, steam stripping study, and high temperature vapor-liquid equilibrium of oil-solvent-steam systems. The experimental methodologies, including the merits and experimental limitations for these measurements are discussed in detail. Example results of heavy oil property measurements for each technique are presented. Finally, a systematic heavy oil characterization workflow is proposed for various types of production processes such as cold depletion, steam flood and heavy oil flow assurance characterization.

Evaluation of Diffusion of Light Hydrocarbon Solvents in Bitumen

“…In either bitumen, the solubility of DME is higher compared to that of propane, even for casese where DME has lower P/P sat compared to propane. Past laboratory studies (Memon et al, 2010) have shown that DME and propane can reduce oil viscosity by a similar ratio, for a similar solvent content present in the oil. The fact that DME has higher solubilty compared to proprane means that, in theory, this solvent may be able to reduce viscosity more effectively than propane vapour.…”

Rheological behavior of water-in-oil emulsions of heavy and extra-heavy live oils: Experimental evaluation

“…Despite the importance of this variable, its influence on mechanical properties has been less studied in comparison to the temperature (Martín-Alfonso et al, 2007). In fact, reports of experimental measurements of viscosities for emulsions under pressure have been very scarce in the literature and the data reported usually do not exceed 10 MPa (Johnsen & Rønningsen, 2003;Kokal & Álvarez, 2003;Albou-dwarej et al, 2007;Memon et al, 2010).…”

“…However, the capillary viscometer is probably the most used instrument for measuring the viscosity as a function of the shear rate for a wide range of materials (Munoz & Yeow, 1996), and therefore could be used for heavy oil viscosity measurements at temperatures and pressures above atmospheric conditions. In addition, it is recommended for viscosity measurements of emulsions because the fluid dynamics is less affected by the relatively low concentration of contaminant fine particle (Memon et al, 2010). This type of viscometer has been used to measure different types of emulsions at low or medium pressures (Memon et al, 2010;Alboudwarej et al, 2007;Alvarado & Marsden, 1979;Muller, Lessnig, Platz & Koepke, 1966;Albers & Overbeek, 1960).…”

“…Two third parts of the worldwide crude oils are produced in an emulsified way; these emulsions are mainly of the water-in-oil type due to the production processes. Dehydration of petroleum reservoir downhole samples is necessary to determine reliable PVT (Pressure, Volume, Temperature) properties for the analysis of the fluid behavior (Memon et al, 2010) and to carry out an efficient management of hydrocarbon reservoirs (Nagarajan, Honarpour & Sampath, 2007). Particularly for heavy and extra-heavy fluids, this dehydration process is commonly very difficult and complex because the formed emulsions are usually very stable.…”

“…Particularly for heavy and extra-heavy fluids, this dehydration process is commonly very difficult and complex because the formed emulsions are usually very stable. In addition, the most known dehydration techniques are only applicable at atmospheric conditions (Memon et al, 2010), which is prohibited to down-hole samples (live oils), because these have been captured at high pressure and high temperature, and therefore need to be analyzed under those conditions.…”