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% [3] ; polymer: polyacrylamide, relative molecular weight of 3.5 million; surfactant: OP-10.

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 [4] .

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 [5] .

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, C_1μm; third is according to oil droplet volume average particle diameter, D[4,3]. Obtained Oil removal rate from the change of oil content, P_1μm.

Concrete evaluation parameter and calculation formula as follows.

The calculation formula of C_1μm:

Among them: V_1μm―Concentration of oil droplet which particle diameter under 1 μm;

C_i―Oil content in sample.

By the evaluation index, the smaller the C_1μm 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.