Oil field emulsion, it's form, condition and the role of emulsifier PPT_Lecture.pptx

Oil field emulsion

1. Oil Field Emulsion Prof. A. D. Ibrahim Sulaiman

2. Introduction A mixture of two mutually immiscible liquids, one of which is dispersed as droplets in the other and is stabilized by an emulsifying agent . The dispersed droplets are known as the internal phase. The liquid surrounding the dispersed droplets is the external or continuous phase. The emulsifying agent separates the dispersed droplets from the continuous phase.

3. Forms of Oil field emulsion : Water-in-Oil (W/o) Emulsion. This is when water is finely dispersed in the oil, and is called normal emulsion. It varies in sizes from large droplet to 1µm (~ 0.00004 in.) in diameter. Oil-in-Water (o/w) Emulsion. Here the oil is dispersed in water. It is also called Inverse Emulsion Multistage Emulsion. This is when a more agitation takes place and a more complex emulsion would form. C ondition for the Formation of Emulsion Existence of two mutually immiscible liquids, An emulsifying agent (stabilizer), and Sufficient agitation to disperse the discontinuous phase into the continuous phase.

4. Role of the Emulsifier The three principal actions of the emulsifier are: Reducing surface tension, F orming a physical barrier, and S uspending water droplets.

5. Emulsion Stability The difference in density between the water and oil phases , The size of dispersed water particles , Viscosity, Interfacial tension , The presence and concentration of emulsifying agents , Water salinity (water Content), Age of the emulsion, Agitation . Type of emulsifier Solids

6. Types of Emulsifiers Naturally occurring surface-active materials normally found in crude oil . Paraffins , resins, organic acids, metallic salts, colloidal silts and clay, and asphaltenes (a general term for material with chemical compositions containing sulfur, nitrogen, and oxygen) are common emulsifiers in oil fields . Workover fluids and drilling muds are also sources of emulsifying agents. Added Chemicals: Corrosion inhibitors, paraffin, dispersants, wetting agents etc.

7. EMULSION FORMATION REGION Flowing well Well head Bottom choke Pumping wells Gas lift wells

8. EMULSION RESOLUTION/TREATMENT Chemical Heating Setting Electrical Filtration or centrifugation and Dilution. Treating with Heater-Treaters Other methods that are not yet fully accepted in the industry Ultrasonic vibration, Extraction and D istillation

9. Important A ctions are required of a D emulsifier : Strong attraction to the oil–water interface , Flocculation, Coalescence, Solid wetting.

10. Chemical Method of Treating Oil-in-water Emulsion The purpose of treating chemicals is to induce coalescence so that the oil and water will separate rapidly. Surface-active agents are absorbed at the oil–water interface, rupture the tough film (skin) surrounding the water droplets, and/or displace the emulsifying agent and force the emulsifying agent back into the oil phase.

11. The procedure for demulsifying oil-in-water emulsions The demulsifier is added to emulsion in the required proportion ; The chemicalized emulsion is agitated to promote coalescence of the oil particles; and Quiescent settling is thereafter provided in a suitable facility to achieve separation of the oil and water, which may be aided by air-gas flotation . Froth flotation procedures may be helpful in accelerating separation of the oil particles.

12. Selection and Injection Points of Chemicals Bottle Test Emulsion-breaking chemicals are most commonly tested with a bottle test, which involves mixing various chemicals with samples of the emulsion and observing the results E liminating some chemicals and selecting those that appear to be more efficient . P rovide an estimate of the amount of chemical required and an estimate of the settling time required for a treating vessel.

13. Cont’d Field Trial A field trial is carried out to test the chemical’s ability to operate in a dynamic system . T he flexibility of the demulsifier to process changes can be established Field Optimization Here, a full-scale field optimization is carried out. Chemical performance is monitored routinely as are the possible side effects of under-or overdosing, such as separator interface buildup. It may be that if the field produces through two or more platforms, injection locations and dose rates may need to be optimized for each location.

14. Conditions Reasons Primary stage Measure X em , X D at room temperature Calculate ∆X= X em -X D The higher the positive difference the better but not absolute indicator of efficiency Secondary Stage Determine optimum efficiency, E m the number of drops to reach, E m , N determine X ro and X rw   The higher, the better   the lower the better due to cost consideration. The higher the Xrw close to X of water, the better or the lower the Xro close to pure oil the better Tertiary stage P H : The less acidic, the higher the P H during treatment         Cost consideration for volumetric requirements (number of drops, N) Shelf life of demulsifier The less significant the change of P H during treatment the better Risk the men and material handling. Acidic demulsifier may damage refinery catalysis and accelerate corrosion problems   The lower the cost the better The older the demulsifier in the shelf, the poorer its performance

15. Keys X em = Dielectric constant of emulsion X ro =dielectric constant of remaining emulsion approximately X of resolved oil at optimum efficiency X= dielectric constant of a sample is the ratio of the capacitance of material (sample) to that of vacuum (air). X D = dielectric constant of demulsifier . X rw = Dielectric const of resolved water ∆X = Dielectric difference, X em - X D Emulsion is likely to be resolved if the dielectric constant of demulsifier is lower or equal to the dielectric constant of the emulsion being treated. Emulsion Resolution Efficiency, K = [( Xem-Xdem )/ Xem ] x 100 %. … ( i ) Where Xem = dielectric constant of emulsion Xdem = dielectric constant of demulsifier K = Emulsion Resolution Efficiency AMA Ratio = HLBem / Xdem ……(ii) For ranking, the higher the K and AMA ratio, the better.