THE EFFECT OF SURFACTANTS USED IN MINING ON THE FORMATION OF HIGHLY STABLE SUBOIL EMULSIONS

ABSTRACT

The results of the analysis of the schemes for collecting and preparing the products extracted from wells show that the main sources of formation of stable water-oil emulsions are rotary devices and pumps, which operate in a turbulent mode of change in temperature, pressure and movement of the emulsion during transportation. The patterns of formation of water globules in the range of Reynolds number values (Re) and depending on the composition of surfactants used to increase well productivity are analyzed. It is known that the main indicators of the efficiency of phase separation processes of stable water-oil emulsions are the duration of their disintegration process (τ), which is determined depending on the diameter of water globules and surfactants contained in the products of producing wells.

АННОТАЦИЯ

Результаты анализа схем сбора и подготовки добываемой из скважин продукции показывают, что основными источниками образования устойчивых водонефтяных эмульсий являются роторные аппараты и насосы, которые в процессе транспортировки работают в турбулентном режиме изменения температуры, давления и движения эмульсии. Проанализированы закономерности образования глобул воды в диапазоне значений числа Рейнольдса (Re) и в зависимости от состава поверхностно-активных веществ, используемых для повышения продуктивности скважин. Известно, что основными показателями эффективности процессов фазового разделения устойчивых водонефтяных эмульсий являются продолжительность процесса их распада (τ), которая определяется в зависимости от диаметра глобул воды и поверхностно-активных веществ, содержащихся в продукции добывающих скважин.

Keywords: Surfactant, Reynolds number, water-oil emulsion, water globules, "Northern Ortabulok" oil production plant, oil viscosity.

Ключевые слова: ПАВ, число Рейнольдса, водно-нефтяная эмульсия, капли воды, Установка подготовки нефти «Северный Ортабулок», вязкость нефти.

Introduction

The presence of associated petroleum gas in the emulsion complicates the separation process, as it acts as an initiator of emulsion formation. Therefore, initially, associated gas is removed from the oil using a separator in order to normalize the subsequent oil preparation processes [1; p. 104-105].

In the traditional technological scheme, before delivering the water-in-oil emulsion (WOE) to the oil preparation equipment (OPE), it is collected in tanks in oil collection reservoir parks, which are transported by several pumps. The collection system operates at high pressure and high flow rates of well products [1; p. 104-105].

In some cases, in wells, the flow is initially transferred to high-or medium-pressure separators located near the oil treatment plants at a certain wellhead pressure, where it mixes with the products from all other wells [1; pp. 23-27].

The transportation of products from production wells to complex processing facilities in the field is carried out mainly using the natural energy of the productive layers and deep well pumps installed at the bottom of the well during the production process. Although these methods extract associated gases from the WOEs, the formation of emulsions with increased stability is observed.

Materials and methods

The analytical results of the schemes for collecting and preparing products extracted from the well show that the main sources of the formation of stable WOEs are rotary devices and pumps, which occur in the turbulent regime of temperature, pressure and emulsion movements during the transportation process. Taking into account the above, we studied the influence of hydro- and thermochemical factors on the formation of stable WOEs.

It is worth noting that fluids (formation water and oil) are practically insoluble and differ sharply from each other in their molecular composition, forming an emulsion, although the principle of mixtures and the laws of surface phenomena (wetting, formation of new phases and friction) are applied to them [3; 60-65 p.].

Therefore, lyophilic emulsions, which have strong intermolecular interactions at the surface boundaries of the dispersed phase and dispersed media, are thermodynamically stable, while lyophobic emulsions are thermodynamically unstable [3; 60-65 p.].

In production practice, in order to increase the level of oil production productivity, various surfactants (for example, XSI-4601) and chemical reagents (in small quantities) are used in production wells, which reduce the viscosity and density of the extracted oils. Therefore, it is considered important to take these methods into account in the formation of stable emulsions during the production process [4; p. 113-114].

Results and discussions

We analyzed the patterns of water globule formation in the range of different Reynolds number (Re) values ​​and depending on the composition of surfactants used to increase well productivity, and the results of the study are presented in Figure 1.

Figure 1. Variation of water globule diameters (D) as a function of the flow regime Re number during well product transfer:

1 - before adding surfactant to the well; 2 - with 1% surfactant added to the well; 3 - with 3% surfactant added to the well

It can be seen from Figure 1 that, depending on the flow regime, as the Reynolds number increases from 2300 to 2600 (in the absence of surfactants), the diameter of the water globules decreases from 35 μm to 26 μm, and as the Reynolds number increases to 2900, the diameter of the globules decreases to 25 μm (curve 1). Adding 1% surfactant to these emulsions reduces the diameter of the water globules in the emulsions from 35 μm to 16 μm (curve 2). Adding 3% surfactant to the emulsion causes the diameter of the water globules to decrease from 35 μm to 3 μm (curve 3). In all three cases, with a further increase in the Reynolds number (Re) criterion, the diameter of the water globules changes almost insignificantly, which confirms the end of the formation of a stable water-oil emulsion with water globules of different sizes. Surfactants added to oil production wells in an amount of 1% to 3% act as emulsifiers and, as a result, contribute to the formation of water globules of smaller diameter, which complicates the processes of phase separation of a stable water-oil emulsion [4; p. 143-145].

It is known that the main indicators of the efficiency of the phase separation processes of stable water-oil emulsions are the duration of their decomposition process (τ), which is determined in a way that depends on the diameter of the water globules and the surfactants in the production well products. The results of the study of these indicators obtained from the “Northern Middle” oil preparation equipment are presented in Figure 2.

Figure 2. Variation in the breakup time of a water-oil emulsion with changing the diameter of water globules:

1 - before adding surfactant to the well; 2 - with 1% surfactant added to the well; 3 - with 3% surfactant added to the well.

As can be seen from Figure 2 below, in all three cases of the study, the time to break up a stable water-oil emulsion decreases sharply with an increase in the diameter of the water globules. In addition, the addition of 1% surfactant (curve 2) or 3% surfactant (curve 3) requires more time to break up a stable water-oil emulsion compared to the case without surfactant (curve 1). This is explained by the fact that the introduced surfactants form smaller water globules that are difficult to sink to the bottom of the reservoirs. Therefore, the introduction of surfactants and chemical reagents into the wells, increasing their oil yield, allows you to accelerate the breakup of a stable water-oil emulsion [4; p. 124-126].

Conclusion

In general, it has been established that the influence of hydrodynamic and thermodynamic factors plays an important role in changing the stability of water-oil emulsions, especially in the formation of water globule sizes, in the dispersed phase and other cases. In practice, their properties vary proportionally depending on the Reynolds number and the emulsion temperature, which is explained by the complex chemical composition of water-oil emulsions containing surfactants. Similarly, the presence of surfactants in water-oil emulsions negatively affects the time of their disintegration process and the formation of large water globules.

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