Due to the production conditions, ** is mostly obtained in the form of water-in-oil emulsions, which are stabilized by asphaltenes, waxes and fine particles. In fact, the first step in refining ** is to separate the water. The aim is to destroy the emulsion in the most cost-effective way and to completely separate the aqueous phase. Surfactants are often used in combination with heat treatment to coalesce and separate water droplets.
*It is a very complex mixture, and its chemical composition and physical properties vary greatly depending on the place of origin. The content of water, salt, and minerals varies greatly. The difference in mixtures will not only affect its viscosity, density and other macroscopic properties, but also affect the type and optimal amount of demulsifier.
As a result, new demulsifiers are constantly being developed in the market. In order to develop and select the right demulsifier, a variety of emulsions must be tested with a number of different demulsifiers. For technical and economic reasons, its optimal concentration must be determined. An effective test method to quantify the separation process in a short period of time would be used as an alternative to the vial test method.
Materials and methods
1.1 Preparation of samples
Two ** emulsions (both black samples) from different production sites were studied, which were noted as Oilfield 1 and Oilfield 2. In addition, 15 ml of oilfield No. 2 sample was loaded into a glass container of about 50 ml, and 18 l of demulsifier solution (corresponding to 0. of the demulsifier dose) were added respectively027vol.054 vol.08 vol % and 012 vol%), shake these samples on a tabletop stirrer at a frequency of 150 min for 30 min. Due to the high viscosity of the fluid, only slight mixing is observed. So, during shaking, place the bottle at an angle and turn it 10 times. Mix manually for 1 min before filling the sample into the sample tube.
Approximately ** emulsion and emulsion after the addition of demulsifier are loaded into a sample tube with a PA10 mm. Before measuring, place these samples in a water bath at 80 °C for half an hour.
Real-time gravity analysis
Real-time analysis was performed using the LumiReader 413 at 60°C, and the sample transmittance curve was recorded every 250 seconds for 17 hours.
Accelerate analytics
The test was performed at 60°C using a Lumiizer 611 (NIR) at 4000 rpm, and the sample transmittance curve was recorded every 30 seconds for 20 minutes.
Results and discussions
Real-timeTesting
Figure 1 At 60 °C, add 0Transmittance pattern of oilfield No. 2** emulsion with 12vol% demulsifier within 17 hours (one for every 25 spectral lines).
As can be seen from the transmittance spectrum in Figure 1, the transmittance at the bottom of the sample indicates the presence of a clear water layer at the bottom.
Fig.2 Oilfield 1, oilfield 2, oilfield 2+0Transmittance spectral line of 12vol% demulsifier tested under standing conditions for 17 h (only the first and last lines are shown), after sample testing**.
Figure 2 compares the separation behavior of two ** samples and field 2 after the addition of demulsifier. The transmittance at the bottom of the sample of oilfield 2 with demulsifier was significantly increased, indicating the formation of a clarifying layer. In the case of no demulsifier in Field 2, there is only a very small change between the first and last profiles, indicating that the sample is stable. In contrast, the oil from Field 1 shows a distinct clarification layer above the bottom.
Fig.3 Graph of integrated transmittance over time (42-47 mm at the bottom of the sample).
As can be seen from Figure 3, the light transmittance of oilfield 2 without demulsifier changes very little, and the separation of oilfield 1 is slightly obvious. After adding demulsifier, the difference in ** can be clearly determined in 1 2 hours.
The volume of the clarified phase separated after 17 h of real-time separation at 60 °C was calculated using the software mode "Interface Trace". Table 1 below shows the percentage of clarifier layer (clarification layer height Total fill height) at a reference transmittance of 10%. The successful exploration of Lumireader in characterization is also introduced.
Table 1 Proportion of clarification layer.
Accelerate testing
Fig.4 Transmittance of oilfield 1, oilfield 2 and oilfield 2+ demulsifier at 2300 g and 60 min for 20 min.
As can be seen from the transmittance spectrum in Figure 4, there is a clear water chromatomy at the bottom of the sample.
As can be seen from the decrease in the distance between the spectral lines, the separation of the water layer gradually slows down. It can be assumed that during centrifugation, the degree of stability of the water remaining in the oil phase increases, since the less stable water has been separated.
Figure 5 Effect of demulsifier content on the stability of oilfield 2 (showing the first and last spectral lines), after sample testing**.
The separation behavior (stability) of the emulsion in oilfield 2 as a function of demulsifier concentration is shown in Figure 5. As can be seen from the variation between the first lines, only when the demulsifier dose is 0At around 054 vol%, the amount of water separated by the first line will increase, and the speed of separation will be further accelerated. When the dosage is 0Above 027 vol%, the water is separated after only 10 s. Within the scope of the study, the degree of separation after 10 s increased slightly with increasing dose.
At the same time, it can be seen that at higher doses of demulsifier, there is only a slight improvement in the degree of separation.
After centrifugation at 2300 g at 60°C for 20 min in the Lumiizer, the volume percentage of the clarified layer separated was calculated using "interface tracking". Table 2 gives the ratio at 10% reference transmittance (net phase height Total fill height).
Table 2 Proportion of clarification layer after accelerated test.
Use Interface Tracking to reference the phase separation interface position of the sample at 10% transmittance (Figure 6). The thickness of the clarified water layer is 129 at the bottomThe difference between the position of 8 mm and the position of the phase separation interface is expressed. It can be noted that "Oilfield 1" contains more water than "Oilfield 2" and can be separated by centrifugation alone. The addition of a demulsifier can significantly improve the water separation, but at 0At the dose of 05 vol%, the degree of separation tended to be stable, and from the first spectral line after 10 s, it can be inferred that the degree of water separation was also slightly enhanced at higher doses.
Figure 6 Comparison of water separation kinetics when centrifuged at 60 g at 2300 g. Boundary** The movement of water at a transmission value of 10%.
Within 5-10 minutes of the experiment, the dehydration behavior of the sample can be determined. Oilfield 1 has the highest thickness of the clarified water layer, the fastest precipitation rate, and the most unstable without demulsifier. After the demulsifier content is added to a certain extent, the precipitation rate of the water layer almost no longer changes, considering the economic benefits, it is recommended that the demulsifier content should not exceed 005vol%。
Conclusion. Gravimetric analysis and accelerated analysis are suitable for the qualitative and quantitative characterization of emulsions, as well as for the evaluation of the effect of demulsifiers.
A real-time stability measurement of 1 2 hours at 60 degrees Celsius can determine the difference between ** with and without demulsifier added.
The accelerated test gave the same sorting, but gave a decisive result within 5-10 minutes. In addition to sequencing, it is also easy to optimize the dosage of demulsifiers. Here, up to 12 different emulsions can be analyzed simultaneously under the same conditions. As a result, accelerated testing is a powerful tool for rapid stability sequencing, demulsifier selection, and dosage optimization.
Original link: Emulsion Stability and Demulsifier Dosage Real-Time and Accelerated Analysis - Dispersion Letters (Dispersion-Letters.)com)