Case Studies of Emulsion Behavior at Reservoir Conditions

Abstract

Most emulsion studies are conducted with depressurized crude/water samples. Can emulsions form in the reservoir at high pressures and high temperatures? The answer to this question is generally anecdotal. This paper provides a unique method and new data from emulsion studies at high pressures and high temperatures. Two case studies will be presented where emulsions were suspected to be the cause of production challenges in several wells. The experiments were conducted in a special visual PVT cell with the capability of observing emulsion phase behavior at reservoir conditions. The effects of several variables on emulsion behavior were investigated including shear, pressure, temperature, watercuts, and asphaltene precipitation tendency of the crude.The first case study is in a field that produces tight emulsions. The results of this study indicate that emulsions can form at reservoir conditions, with mixing, especially if the crude has a propensity to precipitate asphaltenes. The new data suggests that emulsion behavior is closely linked to the presence of fine solids through in-situ dynamic precipitation of organic (asphaltenes) and inorganic salts (scales) as well as fines migration in the reservoir. In the second case study, a series of emulsion tests were performed on bottomhole and wellhead samples from several wells. The results suggests that the emulsions are relatively loose at bottomhole conditions but become progressively tighter with a reduction in pressure and temperature. The tightness of the emulsions was linked to fine solids that stabilize them. These include primarily calcite and sulfur-rich heavy hydrocarbons like asphaltenes, with trace amounts of silicates (clays and/or fine grained silica), iron-rich precipitates and barite.

Methane Hydrate Formation and Dissociation in Oil-in-Water Emulsion

“…The apparatus measures the induction time of hydrate formation and pressure as a function of time during hydrate formation and takes video graphs during the experiments. The system consists of a constant volume hydrate cell with a capacity of 250 cm 3 and a pressure rating up to 20.68 MPa. The cell is a stainless-steel cylinder, where a stethoscopic camera, a thermocouple, and a pressure digital gauge are fitted to the top of the cell.…”

“…Within the reservoir when crude oil remains associated with formation water, emulsions are often formed with mixing and/or changes in the pressure, temperature, and presence of asphaltene, resin, fine solid particle, etc. 3 Again, when such emulsions are associated with lighter hydrocarbon gases, there is a greater possibility of forming hydrates under the conditions of reservoir pressure and temperature. As such, water is invariably produced with crude oil and natural gas.…”

A comprehensive review of emulsion and its field application for enhanced oil recovery

“…Microfluidic devices can be used to simulate the formation process of emulsions, but it is difficult to simulate high‐pressure and high‐temperature environments, pore and throat features, and residual oil distributions. Kokal and Al‐Dokhi reported a novel method to observe and study the characteristics of emulsions in a high‐pressure and high‐temperature environment. The study was conducted in a special visual pressure/volume/temperature (PVT) cell.…”

Role of Asphaltene in Stability of Water-in-Oil Model Emulsions: The Effects of Oil Composition and Size of the Aggregates and Droplets

“…Kokal and Al-Dokhi demonstrated that crudes with a higher tendency of asphaltene precipitation are more likely to form kinetically stable emulsions . Several other research studies emphasize the crucial role of asphaltene in stabilizing crude emulsions and present the hypothesis that asphaltenes could also adsorb on the reservoir minerals and contribute to the stability of emulsions. − Generally, asphaltene precipitation is described by two modeling approaches .…”