Chemical Dehydration: Correlations between Crude Oil, Associated Water and Demulsifier Characteristics, in Real Systems

Abstract

With the aim at finding a method for the selection of a suitable demulsifier for crude oil dehydration, five crude/associated water/effective demulsifier real systems were evaluated in this study. Likewise, based on the existing knowledge about the fundamentals of emulsion stabilization process, the typical characteristics of each element of the systems, which represent the variables or factors governing the process, were chosen. These variables were: in the crude oil, the acidity number, as a measure of its polarity; in the associated water, the salinity; and in the demulsifier, the relative solubility number (RSN). A hypothesis based on the surfactant affinity difference (SAD) model is proposed. This model was adapted to the specific case of crude oil chemical demulsification. A simplified mathematical expression was obtained, which establishes a relation between the crude oil nature, the associated water salinity, and the demulsifier hydrophilicity. The data obtained from the evaluation of the selected characteristics were introduced into the model. As a result, the following empirical relationship was obtained: where S is the associated water salinity and A is the crude oil acidity number, variables which are easily measured. RSN values were calculated and compared with those obtained from experiments. Except in one case, the calculated RSN value approximates very closely the experimental one. It is therefore concluded that this correlation serves to select the appropriate demulsifier to dehydrate a given crude oil, based on the simple procedure outlined above. Introduction Design and selection of demulsifiers for dehydrating crude oils have been performed using the classical bottle test. This consists of a large number of laboratory essays. The results of these tests should be confirmed, validated and improved by field tests. The empirical approach that forces the execution of a large number of rigorous essays, is a consequence of: the multiple factors involved in the emulsion stabilization/destabilization process, the difference between crude oil emulsions, and the changes that take place in these emulsions during the life of the production well. Besides, the techniques used to investigate the main factors related to demulsifier performance are tedious and complicated. Instead, the use of an empirical procedure, like the bottle test, gives the most practical solution. Because of the increasing knowledge of the factors related to formation/breaking of the crude oil emulsion, demulsifier selection could be carried out in the future on a more scientific base. Background Emulsion stability is governed by different factors that characterize a component or have effects on the system:–Water phase salinity and pH,–Oil organic nature (paraffinic, aromatic or asphaltenic), - Relative water/oil surfactant affinity,–Oil/water ratio,–Oil and water viscosity and density difference,–Temperature. At the same time, the affinity or relative solubility of the surfactant in the oil or the water phase depends on the salinity of the water phase, the oil nature, and the temperature. Therefore, in a water/oil/surfactant system, if the surfactant affinity to the oil phase is greater than to the water phase, the system forms an water-in-oil emulsion. P. 601^

Demulsification of Colombian Heavy Crude Oil (W/O) Emulsions: Insights into the Instability Mechanisms, Chemical Structure, and Performance of Different Commercial Demulsifiers

“…In fact, 80% of water separation has been reported for KM 1 and 2. 39 Moreover, a few members of the Cx family, namely, C2 and C6, have shown excellent performance following industrial standards, thereby providing more than 80% of water separation. Other members of the Cx line (C8−C13) exhibit an intermediate performance.…”

“…Furthermore, Figure shows the amount of separated water as a function of the RSN number. This parameter, often used for benchmarking and screening, categorizes demulsifiers in oil or water-soluble in a similar way to how the Hydrophilic–Lipophilic Balance (HLB) parameter does. , Large RSN numbers (>13) can be correlated with water-soluble products, while RSN < 13 numbers are assigned to oil-soluble demulsifiers . Interestingly, when the parameter is in the range of 13 < RSN < 17, surfactants tend to partition at the liquid–liquid interface yielding a Winsor type-III system with maximal water dehydration capabilities .…”

“…Chemical demulsification is still an active area of research, and interest in it has increased even more during the past 5−10 years, primarily due to the shift in production to unconventional hydrocarbons. While the literature is vast 16,35,39,65 in terms of the proper demulsifier type and concentration to deal with heavy and extra-heavy (HCO) emulsions. Thus far, the underlying mechanisms that take place at the liquid−liquid interface and the instability phenomena for phase separation in these systems remain poorly understood.…”

On the bending effects on artificial magnetic conductors

“…The structure of the demulsifier can influence both factors. Shetty et al12 concluded that a demulsifier containing a high percentage of hydrophilic groups and having a low molecular weight could perform very well, Marquez‐Silva et al13 proposed an empirical model that established a relation between the nature of the crude oil, the associated water salinity, and the demulsifier hydrophilicity. This work concentrates on two objects: (1) preparing water‐ and oil‐soluble copolymers derived from a styrene/maleic anhydride copolymer (PSMA) and (2) evaluating these polymers as demulsifiers for breaking up water in petroleum oil emulsions.…”

Demulsification efficiency of some novel styrene/maleic anhydride ester copolymers

“…11 The structure of the demulsifier can influence both factors. Shetty et al 12 concluded that a demulsifier containing a high percentage of hydrophilic groups and having a low molecular weight could perform very well, Marquez-Silva et al 13 proposed an empirical model that established a relation between the nature of the crude oil, the associated water salinity, and the demulsifier hydrophilicity. This work concentrates on two objects: (1) preparing water-and oil-soluble copolymers derived from a styrene/maleic anhydride copolymer (PSMA) and (2) evaluating these polymers as demulsifiers for breaking up water in petroleum oil emulsions.…”