Abstract
Emulsion formation is a very costly operational problem encountered during petroleum production. It occurs when reservoir fluids (i.e. hydrocarbon and formation water) are extremely mixed under shear/turbulence, and in the presence of surface active agents. Several conventional methods already exist to treat crude oil emulsions. These include mechanical vessels, heat applications, electrostatic treatment and chemical methods. Emulsion treatment facilities and demulsifier injection rates are usually designed based on the total production volume of commingled wells leading to specific flow stations or processing terminals.
In principle, all produced emulsions are not intractable. While some wells produce tight emulsions that require sophisticated treatment mechanisms, others could produce highly unstable emulsions that would easily separate into bulk free water and oil phase by gravity actions. Selection and treatment of only the problematic wells would greatly reduce the capital expenditure and operating costs associated with emulsion treatment, especially in large multi-well oilfields. Classifying producing oil wells according to their emulsion tightness requires fundamental knowledge of emulsionbehaviours and their formation kinetics.
This paper presents an experimental procedure for studying the physical behaviours of crude oil - water emulsions. Series of laboratory tests were carried out to study the effects of shear and emulsifiers on the stability of oilfield emulsions at various watercuts. Asphaltenes, reservoir fines and inorganic solids were used as emulsifiers to produce emulsions. A novel method that simulates shearing environment in the laboratory was developed during this research.
Separation rate of the emulsified water from these samples was used as an indicator to measure their tightness. Unique trends describing emulsion tightness at several production conditions were observed and presented as Emuls-K's Emulsion Diagnostic Plots and Equations, EDP and EDE in this paper. These generic empirical models incorporate the 3 main conditions responsible for emulsion formation in an oilfield. They encompass a wide range of watercuts, emulsifier concentrations and shearing energy levels. The diagnostic equations developed were further written in java codes and integrated into an executable oilfield tool designated as EMULS-K APPLICATION. It characterizes the tightness of produced emulsions and helps in the diagnosis of emulsion problems. Its result displays an index of emulsion tightness, ET of the wells analysed.
The technology developed in this study was used to address a real oilfield emulsion problem, with 21 producing oil wells. Emuls-K technology spotted out the wells with relatively high ET values as those producing intractable emulsions. The results obtained from this study strongly correlates with those gotten by a chemical service company using the conventional bottle test approach.
Concept of the Emuls-K innovation will be further validated with more field applications. A digitalized hardware design of the technology will be developed and subjected to operator's technology maturation process
