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Oil and gas separators
The document is a course outline on oil and gas separators, covering types of wells and separation processes. It discusses key concepts like emulsions, hydrates, and paraffins, as well as various separator types and control valves. It also addresses factors that influence fluid separation, such as pressure, composition, and temperature.
Oil and gas separators
- 1. Oil and GasSeparators Petroskills course Hector Nguema Ondo Perez
- 2. Type of wells: Introductionto separation Type of wells 1- Introduction to separators 2- Type of separators 3-Valves in separators Table of contents
- 3. Introduction to separation Emulsions,Hydrates & Paraffins Emulsions: At least one substance is finely dispersed throughout another. Paraffins: sticky, plastic substance that may form plugs in equipment. • Heating fluids to melt the paraffin. • Injecting chemical solvents. • Mechanically scraping it from surfaces Hydrates: Solid formed when mixtures of water vapor and high-pressure gas are cooled. Unless a source of heat is provided or inhibitors are administrated, temperature must be held above the temperature at which hydrates form • Liquid desiccants: Glycol • Solid desiccants: Silica Gel, Sovabeds…
- 4. Introduction to separation FluidSeparations Variables that control fluid separation : • Fluid Pressure • Fluid Composition • Fluid Temperature Low-Temperature separation Flash separation Differential Separation
- 5. Types of separators Verticalseparator Type of extractors Three phase separatorPrimary mist extractor Two phase separator
- 6. Types of separators Horizontalseparators Horizontal separator
- 7. Types of separators Horizontalseparators
- 8. Types of separators Meteringseparator , Cold-feed stabilizer & spherical separators Metering separator Cold-Feed stabilizerSpherical separator
- 9. Valves Separator control valves Liquidlevel control Backpressure regulator Spring Loaded Self Acting valves Safety Valves
- 10.
Editor's Notes
- #3 Crude Oil Well: Gas produced can be free (carried along in the production stream) or, gas can be in solution (dissolved in well fluids). As well fluids reach ground level, pressure decreases and the capacity of the liquid to hold gas in solution decreases, so the gas separates out of the oil. Gas that is produced from a crude oil well is called casing-head gas or associated gas. Dry Gas Well: Gas produced alone or with water is called non-associated gas. Dry gas wells and gas condensate wells produce non-associated gas. Gas Condensate Well: A condensate hydrocarbon is a very light hydrocarbon that changes from liquid to vapor at near atmospheric conditions. As condensate hydrocarbons move from the high-pressure reservoir to a surface line that is near atmospheric pressure, they vaporize. As pressure on condensate hydrocarbons increases, they condense.
- #4 Emulsion: At least one substance is finely dispersed throughout another, usually in the form of droplets. Emulsifying agent form a film around the droplets of water in oil, which must be broken before the two can separate. When the film around the individual droplets of water is broken, the drops coalesce into larger drops, which gradually become heavy enough to settle out of the oil. Paraffins:cools as it flows from the producing formation to the storage or pipeline facility, it can be prevented by: Heat: A portable high-pressure steam generating unit or hot oil can be used to melt paraffin, which then returns to the fluid stream Inhibitors: Using paraffin inhibitors causes paraffin to remain in solution Scraping: Rubber or soluble balls can be pumped through lines or tubing. The balls push paraffin from the lines. Pressure: High pressure causes some paraffins to remain in solution, so increasing process pressure is another way of preventing paraffin buildup
- #5 Pressure: As well fluids reach the surface, pressure on them is decreased, and the fluid's ability to hold gas in solution is decreased. Light fluids begin to separate naturally when the pressure is lowered. Very often, pressure is fixed according to sales-line pressure, so pressure is usually not under the lease operator's control Composition: Gravity alone will eventually cause heavy components to settle out and light components to rise. The lease operator has little control over fluid composition. Temperature: Solution gas released as free gas is held by the surface tension of the oil. To release free gas, the oil temperature is increased. Surface tension is reduced when well fluids are warmed because gases begin to separate as temperature rises. Low Temperature Separators: as the velocity increases, volume increases, pressure & temperature decreases Flash Separation Flash separation occurs as a result of a pressure drop in tubing and lines Differential Separation Differential separation is the separation of gas that occurs in a separator. Differential separation is more complete than flash separation. In a separator, there is enough time and space for heavy vapors to condense. So, differential separation yields a comparatively high proportion of liquid hydrocarbons
- #6 As fluid strikes the baffles, the surface tension holding free gas in the oil is broken. Inertia is resistance to change in direction. The heavier a fluid is, the greater its resistance or inertia. The gas-oil mixture funnels through a narrow opening in the mist extractor cone. Because the stream is restricted in the cone, it moves faster than when it entered the cone. The fluid is forced to flow around the curved vanes in the mist extractor. Dense oil particles fly against the vanes and cling to the separator's sides. Oil droplets fall from the vanes onto the top of the cone and run down the separator's sides, flowing into the drain at the edge of the cone. The light gas continues rising through the separator to the secondary mist extractor -Secondary Mist is made of wire mesh. The gas flows around the wires, but the oil droplets impinge on the wires. -The mist extractor in this separator is designed to remove large quantities of residual liquid mist from gases. The stream of gas and liquids flows through and impinges against (hits) several layers of vanes. -Coalescing pack mist extractors remove liquid from gas streams. The rings in the coalescing pack change the direction of flow. Gases are whirled as they curve around each ring. The heavy liquid traveling with the gas impinges on the rings, collects and falls. Coalescing packs are effective, but they tend to foul because the rings are close together. Because free water does not settle out in the time it takes for the oil and gas to separate, three-phase separators require a longer retention time than two-phase separators
- #7 When well fluids first enter the separator they strike the angle baffle. Forward motion is temporarily stopped and heavy liquids fall immediately to the bottom of the separator. Gases and oil spray continue through the defoaming element, or primary mist extractor. There, the baffles change the direction of flow. A vertical separator has a smaller bottom area than either the horizontal or spherical separator, which makes it easier to clean. And, because of its height, the vertical separator can handle more sand and mud than the other separators. So, a vertical separator is more practical on a crude oil well if it is likely to produce sand or mud. The depth of a vertical separator also provides the space to handle liquid surges more easily than a horizontal separator.
- #9 Metering separators contain inlets and mist extractors similar to vertical separators. In addition, they have separate chambers used to meter, or measure, the fluids a well produces. This drawing represents the lower portion of a metering separator. This separator has three chambers. In the upper chamber, oil and water are separated. Then they flow through separate lines into metering chambers in the bottom. The float travel controls the volume of liquid entering and leaving the metering chamber with each dump. When the float is at its low position, the liquid level control pilot opens the inlet valve to the metering chamber, and closes the outlet valve. As it reaches its upper position, the float triggers the liquid level control pilot, closing the inlet valve and opening the outlet valve. The liquid is discharged from the metering chamber. Each time the outlet valve is opened, the same volume of fluid is discharged from the metering chamber. A counter attached to the liquid level control pilot registers each time the outlet valve opens. The pressure equalizing line provides an outlet for the gas in the metering chamber so that pressure cannot prevent liquid from entering the metering chamber. Liquid stabilization systems remove most non-condensable vapors from the liquid while holding condensed vapors, making fluids more stable. Stable liquid hydrocarbons lose few condensable vapors in the stock tank, making the stock tank more stable. They also cause little turbulence in the tank and have usually been differentially separated. At high temperatures, light liquid components begin to vaporize. Even when they have been differentially separated, stock tank liquids can lose condensable vapors at high temperatures. As the liquid loses hydrocarbons, the volume and API gravity decreases, resulting in a lower sales price.
- #10 This liquid level control operates a dump valve in the oil outlet. As production increases, liquid level rises and the dump valve opens. When the float moves down, the valve lever moves up and the valve closes. When the liquid and the float rise to the desired level, the valve opens. backpressure regulator. Pressure applied under the diaphragm causes the weight to rise and the valve to open. With no upstream pressure under the diaphragm, the weight falls and the valve closes. Some disadvantages of backpressure regulators are: If the weight begins moving up and down, its momentum can cause it to overshoot. Weight-loaded backpressure valves are best suited for steady production streams. Backpressure valve linkage is exposed to the atmosphere, which can cause the pivots to become rusty or dirty. Rusty or dirty pivots prevent the valve from moving freely. The pivots can work loose, preventing the valve from operating properly These are spring-loaded self-acting valves.In both valves, the spring pushes against the diaphragm to close the valve. Separator pressure is applied below diaphragm A and above diaphragm B. The valves open as pressure in the separator increases.The amount of backpressure maintained is adjusted by increasing or decreasing spring tension against the diaphragm. For spring-loaded valves to operate smoothly, valve stems must be clean and free to move. The valves will not operate if the packing is too tight.Valves are self- or direct-acting when the controlled pressure is used to operate the valve.
- #11 The slotted T through which the pivot moves can be adjusted by rotating the T on the control pivot. Changing the position of the T in relation to the nozzle adjusts the pressure maintained in the separator. The nozzle is stationary, so rotating the T to the left moves the flapper closer to the nozzle. By increasing or decreasing the distance between the flapper and nozzle with the control adjustment, nozzle tube pressure changes just as it does when the bourdon tube straightens and coils. When the flapper is close to the nozzle, it takes less pressure in the bourdon tube to open the valve than if the flapper were far from the nozzle. Raising the pivot decreases bandwidth or operating range. Lowering the pivot increases bandwidth. Raising the pivot results in relatively fast valve action while lowering the pivot results in relatively slow action. Gas flowing into the nozzle must be clean and dry. This regulator includes a filter to clean gas before it enters the nozzle. If the gas-water content is high, it should be dried upstream of the regulator