In recent years, the water content of oilfield production fluid is high and there is a large amount of oily sewage. In order to improve the capability of sewage treatment, usually using demulsifier for oily sewage processing. This article uses simulated water sample to test the treatment effect of the optimized reverse demulsifier at different oscillation time. As the increase of action time and oscillation, the average size of droplets increases and the amount of the droplets under 1 μm decreases.
At present, the moisture content of the produced liquid has been reached over 95% in Daqing Oilfield. Therefore, to improve the rate of oily sewage separation and enhance the ability in waste-water treatment are becoming an important task [
Simulation water sample consisting of two parts: oil sample and water sample. Oil sample: outer transportation crude oil of Daqing Oilfield co.LTD. the first Oil Production Plant Zhongyi Joint Station; Water sample: artificial water sample which prepared according to the free water produced fluid’s water quality analysis data. The date gets from oil well of Zhongyi Joint Station, it’s formula is: w(NaCl) = 0.1995%; w(NaHCO3) = 0.3024%; w(Na2CO3) = 0.0171%; w(Na2SO4) = 0.0001%; w(CaCl2) = 0.0002%; w(MgCl2∙6H2O) = 0.0007% [
The first step of preparing simulated water sample is the mother liquid. Mother liquid is an emulsion, it’s oil content is 50%. The step of preparing: Add 1500 mg/L polymer (molecular weights of 3.5 million) to the jar of 5000 ml, 100 g of distilled water, it’s content of surfactant (OP-10) is 1000 mg/L; The purpose of adding polymer and surfactant is to prepare a stable emulsion. Add 100 g of oil sample to a jar then put the jar in 45˚C constant temperature water bath for 60 min. Use the oil sample and the water sample in jars to prepare oil particulate mother liquid of 50% oil content (with the measurement of particles distribution instrument, the average diameter of oil particulate is 2.44 μm, the distribution of oil particulate diameter is 0.85 - 5.85 μm). Date processing apparatus is T25 type of homogeneous instrument produced by the IKA Company in Germany. Emulsify in 20,000 r/min rotating speed for 7 min. In this process, homogeneous instrument placed in 45˚C incubator to keep the temperature constant.
The mother liquid is ready, we can prepare the simulated water sample. The process: Add 398.4 g of water sample into a plastic bottle of 600 ml then added 1.6 g of oil particulate mother liquid prepared already. After shaking with hands for 20 times, we get the simulated water sample of 2000 mg/L oil content. Now the content of polymer is 3 mg/L in the water sample, it will not influence the property of water sample.
Refer to the drug concentration of practical field. The choices of drugging concentration are 5 mg/L, 10 mg/L, 20 mg/L. To facilitate the evaluation, each oscillation time has two water samples, an adding sample, a blank sample. According to the experimental results of previous optimal selection reagent, the reagent in adding sample is S1 [
Experimental procedure: put two plastic bottles with simulated water sample in the 45˚C constant temperature water bath for 60 min, then add 1.6 g of oil particulate mother liquid and shake 20 times with hand. Of which one plastic bottle added S1 of 5 mg/L, making it as the adding sample, another bottle is the blank sample. Add about 8 g crude oil into both of bottles, then put bottles in vibrator shake in 360 r/min for 15 min. Set the vibrator in 45˚C incubator during shaking, to keep a constant temperature. After shaking, make bottles standing for 15 min then measure the oil content and the distribution of oil particulate diameter in lower water. Change drugging concentration. Repeat the same method. Drugging concentration is respectively 10 mg/L, 20 mg/L.
Oscillation time determined by the flowing time of produced water in pipe. The choices of oscillation time are 15 min (between booster station and joint station), 30 min (between metering station and booster station, close to booster station), 60 min (between metering station and booster station, in the middle), 90 min (between metering station and booster station, close to metering station), 120 min (between oil well and joint station).
To facilitate the evaluation, every oscillation time has two water samples, an adding sample, a blank sample. According to the experimental results of previous optimal selection reagent, the reagent in adding sample is S1, concentration is 20 mg/L. Experimental procedure: put two plastic bottles with simulated water sample in the 45˚C constant temperature water bath for 60 min, then add 1.6 g of oil particulate mother liquid and shake 20 times with hand. Of which one plastic bottle added S1 of 20 mg/L, making it as the adding sample, another bottle is the blank sample. Add about 8 g crude oil into both of bottles, then put bottles in vibrator shake in 360 r/min for 15 min. Set the vibrator in 45˚C incubator during shaking, to keep a constant temperature. After shaking, make bottles standing for 15 min, then measure the oil content and the distribution of oil particulate diameter in lower water. Change oscillation time. Repeat the same method. Oscillation time is respectively 30 min, 60 min, 90 min, 120 min [
Drugging effect evaluation has three ways, first is according to the minimum 10% particle diameter, D10; second is according to oil droplet under 1 µm, C1μm; third is according to oil droplet volume average particle diameter, D[4,3]. Obtained Oil removal rate from the change of oil content, P1μm.
Concrete evaluation parameter and calculation formula as follows.
The calculation formula of C1μm:
Among them: V1μm―Concentration of oil droplet which particle diameter under 1 μm;
Ci―Oil content in sample.
By the evaluation index, the smaller the C1μm means drugging do better on reducing oil droplet under 1 μm than blank sample. The greater the D[4,3] means drugging do better on increasing oil particulate diameter.
The experimental results are shown in Tables 1-5.
According to the
Drugging concentration | Blank | Drugging | Evaluation index | ||
---|---|---|---|---|---|
Oil content mg/l | D10 μm | Oil content mg/l | D10 μm | P1μm | |
5 mg/l | 351.75 | 1.68 | 146.16 | 1.81 | 58.45% |
10 mg/l | 467.2 | 1.64 | 64.1 | 2.06 | 86.28% |
20 mg/l | 381.56 | 1.82 | 28.72 | 2.35 | 92.47% |
Drugging concentration | Blank | Drugging | Evaluation index | ||
---|---|---|---|---|---|
V1μm (%) | C1μm (mg/l) | V1μm (%) | C1μm (mg/l) | P1μm | |
5 mg/l | 1.36 | 4.78 | 0.7 | 1.02 | 0.214 |
10 mg/l | 2.56 | 11.96 | 0.65 | 0.42 | 0.035 |
20 mg/l | 1.8 | 6.87 | 0 | 0 | 0 |
Oscillation time min | Oil content (mg/l) | D10 (μm) | P1μm | ||
---|---|---|---|---|---|
Blank | Drugging | Blank | Drugging | ||
15 | 862.7 | 342.0 | 1.56 | 1.61 | 60.36 |
30 | 528.8 | 143.6 | 1.38 | 1.61 | 72.84 |
60 | 486.8 | 188.5 | 1.38 | 1.51 | 61.27 |
90 | 363.6 | 162.2 | 1.47 | 1.65 | 55.39 |
120 | 335.7 | 123.6 | 1.82 | 1.87 | 63.17 |
Oscillation time min | V1μm (%) | C1μm (mg/l) | P1μm | ||
---|---|---|---|---|---|
Blank | Drugging | Blank | Drugging | ||
15 | 1.74 | 0.28 | 15 | 0.96 | 0.064 |
30 | 2.13 | 0.98 | 11.26 | 1.41 | 0.125 |
60 | 4.01 | 3.64 | 19.52 | 6.86 | 0.35 |
90 | 4.1 | 3.7 | 14.91 | 6.00 | 0.403 |
120 | 1.71 | 1.51 | 5.74 | 1.87 | 0.325 |
Oscillation time min | D[4,3] (μm) | The ratio of the volume average particle size (drugging/blank) | |
---|---|---|---|
Blank | Drugging | ||
15 | 2.32 | 2.82 | 1.22 |
30 | 2.2 | 18.62 | 8.46 |
60 | 3.45 | 17.35 | 5.03 |
90 | 22.89 | 33.2 | 1.45 |
120 | 19.96 | 73.6 | 3.69 |
concentration is 5 mg/L. 20 mg/L is the best.
According to the
Analysis and processing of data with Excel. The experimental results are shown in Figures 1-5.
From
We can get from
From
With the increase of the oscillation time, the concentration of oil droplets in the size of less than 1 μm is increasing. The reason may be that the oscillation time is too long, make some of the oil droplets to break into small oil droplets; or may be large droplets have risen to the top of the simulated water sample, the oil content in the lower part of the water is reduced, which makes the proportion of small oil droplets increase.
Because the C1μm is the product of the V1μm and the Ci. Therefore, the variation of its oscillation time depends on the oil content and the concentration of oil droplets.
As can be seen from the
1) Drugging can increase the minimum 10% particle diameter and the volume of the average particle diameter and decrease the concentration and content of oil droplets under 1 µm, oil content.
2) With the increase of drug concentration, oil removal rate increased gradually, minimum 10% particle diameter and volume of the average particle diameter increased, the concentration and content of oil droplets under 1 µm is higher.
3) With the increase of the oscillation time, the basic trend is that the oil content is decreased, the minimum 10% particle diameter and the volume of the average particle diameter increases, the concentration and content of oil droplets under 1 µm is higher.
This work was supported by the National Natural Science Foundation of China (No: 51404072).
BaojunLiu,WantingSun,LipingGuo,ChengtingLiu,MathiasVanflieberge,ChamberJan, (2015) Experiment Study of Reverse Demulsifier on Simulated Water Sample Treatment at Different Oscillation Time and Different Concentrations of Drugging. Open Journal of Applied Sciences,05,764-770. doi: 10.4236/ojapps.2015.512072