Aegis Tech Line Aegis Chemical Solutions Technical Newsletter Volume 06, June 2018

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Janice Patrick
5 years ago
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EMULSIONS IN OIL PRODUCTION CRUDE OIL SPECIFICATIONS Pipeline Operators and Refiners set specifications on the quantity of basic sediment and water (BS&W) in the crude oil that enters their equipment

The specification varies depending upon the contract between the producer and the refiner (or pipeline operator). Heavy crude in California typically has a 3% maximum BS&W on crude leaving the lease.

1 EMULSIONS IN OIL PRODUCTION CRUDE OIL SPECIFICATIONS Pipeline Operators and Refiners set specifications on the quantity of basic sediment and water (BS&W) in the crude oil that enters their equipment and facilities. Crude with high BS&W may not be accepted by a refiner, or the refiner may accept it only at a lower price. The specification varies depending upon the contract between the producer and the refiner (or pipeline operator). Heavy crude in California typically has a 3% maximum BS&W on crude leaving the lease. However, most refiners have a specification of 1% BS&W maximum. A specification of <0.5% BS&W have been reported. Some refiners may also have a specification on the amount of salt in the crude, expressed in pounds per barrel. Larger oilfields that ship crude oil by pipeline have automated BS&W monitors, with controls to divert production or even shut in production if the limits are exceeded. Smaller fields may collect the crude in tanks and ship via trucks. In this case the oil tanks are thieved and centrifuged to determine BS&W before shipment. DEFINITION OF EMULSIONS An emulsion is a dispersion (droplets) of one liquid in another immiscible liquid. The phase that is present in the form of droplets is the dispersed or internal phase, and the phase in which the droplets are suspended is called the continuous or external phase. For produced oilfield emulsions, one of the liquids is water and the other is crude oil. A regular emulsion is one in which water is the dispersed phase and oil is the continuous or external phase. This is also called a water inoil emulsion. The amount of water that emulsifies into crude oil varies widely. It can be less than 1% and sometimes greater than 80%. A reverse emulsion is one in which oil is the dispersed phase and water is the continuous or external phase. This is also referred to as an oil in water emulsion. The amount of oil that emulsifies into water varies widely from less than 1% to over 50%. For emulsions to form, there must be two (or more) immiscible liquids, agitations and emulsifying agents. Emulsifying agents include the following: Natural Surfactants Formation Solids (clays, silt, etc.) Sand Paraffin/ Asphaltenes Corrosion By products Other chemicals Drilling Muds The stability of emulsions depends on the following: Emulsifying Agents Present Temperature of the emulsion Viscosity of the crude oil phase of the emulsion Number and size of water droplets per unit Volume of fluid Gravity differential between oil and water phases (Stokes Law) Protective layer that covers the water droplet (emulsifying agent) Common Household Emulsions Regular Emulsion (water in oil) The components of emulsions are: Continuous Phase Dispersed Phase Emulsifying Agents 1 P age

2 Regular Emulsion with Added Emulsion Breaker Reverse Emulsion with Reverse Emulsion Breaker What is API Gravity? 2 P age

3 Oil API Gravity of Familiar Crude Oils (Generally, the lower the API gravity, the higher the viscosity of the oil) Variation of Viscosity with Temperature and API Gravity 3 P age

ORIGINS OF EMULSION FORMATION There are many locations in oil & gas production systems where emulsions can and will form given the right circumstances: Oilfield Emulsion Handling Equipment There are

4 Note that (d1 d2) is density difference between oil and water and the greater the density difference, the faster the separation. Notice that the Greek letter mu is viscosity of the continuous phase in the equation, and the higher the viscosity, the slower the separation. ORIGINS OF EMULSION FORMATION There are many locations in oil & gas production systems where emulsions can and will form given the right circumstances: Oilfield Emulsion Handling Equipment There are several vessels / equipment designed to help resolve the emulsions that are created during the production of oil & gas. These include: Draw Down Region near wellbore and across perforations or fractures Gas Lift Valves Pumps Chokes Commingling Points Pressure Drop Points Temperature Drop Points Separator (2 phase and 3 phase) Gunbarrel Heater Treater Chemelectric 4 P age

5 3 Phase Separator 5 P age

6 Vortex Separator Electrostatic Treater 6 P age

7 Chemelectric Gunbarrel 7 P age

demulsifiers: Chemical demulsifiers work by deactivating the emulsifying agents the surface active nature of the chemicals allows them to move to the interface where they can act upon the emulsifiers.

8 DESTABILIZING EMULSIONS Once an emulsion has formed, there are a few mechanisms that will destabilizes it and cause the liquids to separate. These include: Agitation to cause droplet contact and coalescence Heat Electrostatic energy Gravity or settling time Addition of light oil or salty water to increase gravity differential Chemical demulsifiers: Chemical demulsifiers work by deactivating the emulsifying agents the surface active nature of the chemicals allows them to move to the interface where they can act upon the emulsifiers. There are a few factors that contribute to demulsification: o Heat o Demulsifier chemicals o Retention time o Agitation The steps in the demulsification process when using a chemical demulsifier are: o Introduction and mixing of the demulsifier in the oil phase of the emulsion o Demulsifier migrates to the oil/ water interface o The barrier at the interface is disrupted o Water droplets collide and coalesce o The enlarged water droplets settle and sweep Combinations of all the above Steps in the Coalescence Process CONSIDERATIONS WHEN SELECTING/DESIGNING A DEMULSIFIER The following must be considered when selecting or developing a demulsifier: Solubility in the Oil Solubility (dispersibility) in the water Overtreat Tendency Overtreatment occurs when enough chemical is present that it becomes the emulsifying agent. Compatibility with other chemicals BASIC DEMULSIFER TYPES There are a few basic demulsifier types as follows: Phenolic Resins Coalescence and IF Control Esters IF Control and Top Oil Dryness Polyol Block Polymers Top Oil Dryness Sulfonates/ Sulfates IF Control and BS Resolution Polyamines IF Control and Solids Wetting Alcohol Oxyalkylates Solids Wetting DEMULSIFIER SELECTION Bottle Tests 1. Selection of Samples 2. Determination of Test Conditions 3. Determining Ratio Tests 4. Screening Test 5. Elimination Test 6. Confirmation Test Treating Stages Samples must be representative of fluids to be treated 8 P age

9 Models System (Test Conditions) System Diagram Temperature and pressure of vessels Production Rates (oil/gas/water) Residence times of all vessels Chemical injection points Export/Shipping specifications Chemical Limitations (Flash Point, Pour Point) All chemicals used upstream of test Relative Test Always run a standard Always run a blank Keep the number of bottles at reasonable level If chemical fails in the system it should fail in the bottle Repeat the tests Determine minimum and maximum treating levels (ratio test) Do everything the same way each time Samples Extreme care: follow all safety protocols Samples must represent the fluids to be treated (Chemical Free) Choose sample point at turbulent flow Sample should be taken in a clean, sealed container Beware of aging Loss of Gasses Loss of Light Ends Oxidation of Crude Components Alteration of Solubility/ Arrangement of Asphaltenes Critical Performance Characteristics Top Oil Dryness Water Clarity Interface Sharpness Chemical Rate Temperature / Agitation Solids Wetting Improving Chemical Performance Chemical injection upstream of turbulent or shear location within system Inject chemicals further out into the system Temperature should be above the pour point of the crude Vessel Fluid Levels Inject chemical into the emulsion Dilute product vs. Concentrated product Chemical Optimization Monitor system BS & W leaving all production vessels Check treater/ Chemelectric for pad Decrease demulsifier injection rate Check system BS & W leaving all vessels periodically for at least 2x the system retention time Adjust chemical rates accordingly Trouble Shooting Treatment Problems System Changes chemicals normally do not stop working o Vessel Levels o Well Shut Ins o New Well Start Ups o o Vessel Temperatures System slugs from outlying platforms or subsea installations Recycling of Fluids Chemical Pump Failures Chemical Interactions Chemical o o o Chemical delivery at time of problem Correct chemical Chemical Contamination CHEMICAL DOSAGE RATES Chemical dosage rates are usually established by bottle testing in the field, and then optimized once applied to the system. Typical test rates range from ppm. (Determined from Ratio Test) Typical treating rates in the system vary from ppm 1 qt. / 100 Barrels = 60 ppm Treating ppm / 60 ppm X # 100s Bbls. = Treating qts. Treating qts. X 60 ppm / # 100 Bbls = Treating ppm 9 P age

10 TESTING EQUIPMENT Thief Syringe Mechanical Shaker Centrifuge Hot Water Bath Micro liter Syringes Centrifuge Tubes 10 P age

EVALUATION OF TEST RESULTS Once the demulsifier is applied either in a pilot test or to the field, the effectiveness of the demulsifier must be done: Record water drop times Thief bottles Grind out

11 EVALUATION OF TEST RESULTS Once the demulsifier is applied either in a pilot test or to the field, the effectiveness of the demulsifier must be done: Record water drop times Thief bottles Grind out thief samples with and without chemical Record results DEMULSIFIER JUSTIFICATION The demulsifier effectiveness and costs associated with its use must be used as justification of the demulsifier. This should consider the following: Chemical consumption and injection points Treating vessel temperature and pressure Profile of BS&W in treating vessels Oil levels and oil pad in vessels Condition of separated water % BS&W of shipping oil 11 P age

12 AEGIS FACILITIES LOCATIONS Corporate Headquarters Houston 4560 Kendrick Plaza Dr., #190 Houston, TX Tel: (855) Permian Basin Breckenridge 566 FM 2231 Breckenridge, TX Tel: (254) Permian Basin Monahans 1332 PR Thrasher Ln. Monahans, TX Tel: (432) x1080 East Texas Teague 931 W. Hwy 84 Teague, TX Tel: (903) x1058 South Texas Cuero 424 U.S. Hwy 87 S. Cuero, TX Tel: (361) North Louisiana Haughton 140 Sligo Industrial Dr. Haughton, LA Tel: (318) x1056 Mid Con El Reno 801 N. Willie L. Minor, #B 1 El Reno, OK Tel: (830) Permian Basin Midland 2200 Market St. Midland, TX Tel: (432) Permian Basin Forsan 300 1st St. Forsan, TX Tel: (432) East Texas Kilgore 4524 State Hwy 42 N. Kilgore, TX Tel: (903) South Texas Freer 5743 Hwy 44 Freer, TX Tel: (361) South Texas Jourdanton 8229 S. State Hwy 16 Jourdanton, TX Tel: (830) South Louisiana Elizabeth 3552 Highway 10 Elizabeth, LA Tel: (318) Mid Con Hennessey 1117 S. Main St. Hennessey, OK Tel: (580) Permian Basin Abilene 4657 FM 707 Abilene, TX Tel: (325) Permian Basin Lubbock Hwy 87 S. Slaton, TX Tel: (806) East Texas Raywood Hwy 90E Raywood, TX Tel: (409) South Texas Asherton 664 Hwy 190 Asherton, TX Tel: (830) South Texas San Antonio 311 N. Frank Luke Dr., #103 San Antonio, TX Tel: (210) Mid Con Ratliff City P.O. Box 98, 1500 Old Hwy 7 Ratliff City, OK Tel: (580) P age

OIL AND WATER SEPARATION AT ITS BEST

OIL AND WATER SEPARATION AT ITS BEST Looking for faster and more efficient separation of produced water from crude oil as well as increased production? Vessel Internal Electrostatic Coalescers (VIEC) have