Effect of Temperature and Pressure on Contact Angle and Interfacial tension of Quartz-Water-Bitumen Systems

ABSTRACT

Thermal recovery methods (such as steam injection) are recent remarkable technologies to recover bitumen from oil sands. The injected steam contacts the oil sand and forms an interface. The steam changes to water transferring its heat to bitumen across this interface. The heated bitumen will have a lower viscosity, mobilize and recover from the reservoir.

Study on hot water-bitumen interfaces should be crucial in understanding the thermal recovery methods. The strength and energy of hot water-bitumen interfaces are expected to play important roles in the recovery of bitumen from oil sands.

However, measurements on hot water-bitumen interfaces are not apparent in the literature. A relevant measurement would be the contact angle and interfacial tension of the waterbitumen interfaces at different temperatures. In this paper, it has been attempted to reveal and present the results of several water-bitumen contact angle and interfacial tension measurements. The measurements cover a temperature range from ambient to 100 ° C for a given pressure.

The experiments are run in x-ray transparent cells and images are taken using a micro-CT scanner. The results of contact angle and the interfacial tensions of hot water-bitumen interface are produced by using the axisymmetric drop shape analysis (ADSA) method.

Introduction

Thermal recovery of bitumen causes many changes in the oil sand reservoirs and in fluids properties such as viscosity, density of each fluid, interfacial tension and wettability of the aqueous-hydrocarbon and rock-fluid interfaces.

Wettability measurement in the oil recovery industry is quite popular and several different methods have been used to characterize the wettability of different reservoirs. These methods are reviewed in detail by Anderson (1) . They are generally categorized in two major groups; qualitative and quantitative methods.

Common qualitative methods for wettability measurement are imbibition rates, microscope examination floatation, glass slide method, relative permeability curves, permeability saturation relationships, capillary pressure curves, displacement capillary pressure, reservoir logs, nuclear magnetic resonance (NMR) and dye adsorption.

Quantitative methods include contact angle, spontaneous and forced imbibition (Amott) and USBM wettability method. According to Anderson (1) the contact angle method is used to measure the wettability of a certain surface, but the Amott and USBM methods are used for core wettability measurements. Quantitative methods are more commonly used; nevertheless, there is no single universally accepted method.

Contact angle ( Θ) is the angle at which a fluid-fluid interface meets the solid surface .The Θ is always measured relative to the denser phase. In this work, water is the dense phase. The contact angle method is very useful for wettability measurement when working with clean surfaces and pure fluids. Typically contact angle measurements are done on oil-waterquartz surface systems in order to study the wettability variations under different temperatures and pressures.

For the measurement of Θ two immiscible fluids are placed on a solid surface; fluid 1 is the denser fluid. ( Θ) can vary between 0 ° and 180 °. If Θ is less than 75 °, fluid 1 is the wetting phase and if Θ is more than 105 ° fluid 2 is the wetting phase.

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