OPERATION OF HEATER TREATER

OPERATION OF HEATER TREATER

1. It is a horizontal vessel employing a vertical flow pattern. Heater treater employs method of heating , chemical action , electrical coalescence , water washing of oil and settling for demulsification of oil .
2. Movement of fluid through heater treater is controlled by a system of differential pressure combined with static heat .
3. Heater treater vessel is divided into four parts .
   i  . Inlet degassing section
   ii . Heating section .
   iii. Differential oil control chamber .
   iv. Coalescing section

INLET DEGASSING SECTION

Oil mixed with demulsifying chemical enters the heater treater through degassing section , above the fire tubes . Free gas is liberated from the flow stream and is equalized across the entire degassing and heating areas of the treater . The  degassing section , is separated from the heating section by baffles .The fluid travels downward from the degassing area and enters the heating section under the fire tubes through multiple orifice distributors .

HEATING SECTION

Heating section consist of a fire tube bent at 180°.

In 6ft. × 15 ft . heater treater , there is one tube ; in 8ft. × 20 ft . heater treater , there are two tubes . The constant level in this section is maintained by weir height . Oil enters this section from bottom of degassing section and passes through  heater at bottom and washing action takes place and free water and solids fall out of the oil stream . The water level in this section is controlled by a weighted , displacement type interface float which operates a water discharge control valve by instrument air acting on diaphragm . The oil allows water flow upward from the distributors section, surrounding the fire tubes , where the adequate temperature is attained .The increase in temperature of the oil releases some additional gas . The heat released some additional gas . The heat released gas then joints the free gas from the inlet section and is discharged from the treater through a gas back pressure control valve .

DIFFERENTIAL OIL CONTROL CHAMBER

The fluid which is heated should be transferd from the heating section over the fixed weir into a differential chamber for oil control , which contains a liquid level control float . The fluid travels downwards to near the bottom of the differential oil control chamber where the opening to the coalescing section distributors are located .

COALESCING SECTION (ELECTRICAL CHAMBER )

Heater treater operates under a high voltage potential on the electrodes for merging of the water droplets in the final stage of processing . The electrodes are suspended on the insulated hanger from the upper portion of vessel . The ‘Ground’ electrode is made up of solid steel hangers to provide proper grounding with the steel of the treater .

An externally mounted , oil immersed high voltage transformer is designed such that to provide the proper power supply to the electrodes .The transformer uses 240 volts in primary and supplies 16500 volts in secondary .The secondary unit having a high voltage is connected to charged electrode through a high voltage entrance which is specially designed in the form of a bushing for insulation .Secondary is also connected to voltmeter and external pilot indicator light .The oil and entrained water enter the coalescing section from the differential oil control chamber through multiple ,full length , metered distributor .As the oil and transformed water come into contact with each other the electrical field produced in the grid area, final coalescing of the water take place .

The water supply which is falling back into the water area at the bottom and the clean oil starts continuously rises to the top portion, and finally it enters at the collector and is comes out through the clean oil outlet of the control valve .

BLOW OUT PREVENTER (BOP)

BLOW  OUT  PREVENTER   (BOP)

It  is a large specialized  valve used to seal  control and monitor oil and gas wells . BOP’s where developed to copup extreme  eratic  pressure  and uncontrolled  flow (formation vick ) from the well reservoir during drilling . kicks can load to potentially catastrophic damage or eratic called blow out .
               In addition to control the down hole (occurring in the drill hole ) pressure and antiflow of  oil and gas , BOP ‘s are intended to prevent tubing (eg: drill pipe and well casing ).Tools  and drilling fluids  are being blown  out of the well when  blow out threatens .
              BOP’s are  critical  to the safety  of the crew , rig equipment system  and  environment and the monitoring and maintenance of well integrity. These BOP’s are intended to be a fail-safe  device. The  BOP  is secured to  the drilling  platform and is used during the drilling process  to monitor and control the  the flow andprerssures of oil and gas that fluctuate during drilling. The BOP is to prevent damage to the rig and crew in the event of blow

RAMS  IN BLOW OUT PREVENTER

BOP  is  usually  consist  of  a  variety  of  different  rams  stacked  vertically .  Each  ram  in  the  stack  has  specific  function  that  is  used  in  different situations .A ram-type BOP works with a pair of opposing steel plungers called rams. The rams are again extend toward the center of the wellbore in order to restrict flow or allows opening in order to permit flow. The interior portion as well as the top faces of the rams are connected with some materials made up of elastometric seals called packers that press against each other, against the wellbore, and around the tube which is running inside the wellbore. Outlets at the sides of the BOP housing (body) are used for connection to choke and kill lines or valves.

1. PIPE  RAMS
   The  pipe  rams  close  around  the outside  of the drill pipe  restricting , the  flow in the  space between  the drill and the wellbore also  known as the annulas .
2. BLIND  RAMS
   The  blind  rams can seal off the  well  if  there  is no pipe in  the  well .
3. BLIND  SHEAR RAMS
   The  blind  shear rams can seal off  the  well  even when there is a pipe  in the well  by  cutting through the pipe

PROPERTIES OF CRUDE

DENSITY AND API GRAVITY

Density : Mass per unit volume
API Gravity : Crude density is commonly measured in API Gravity

FLASH POINT

The lowest   temperature at which a volatile liquid can vaporize to form an ignitable mixture in air.

RVP (REID VAPOUR PRESSURE)

It is the pressure exerted on the surface of the crude at 100f under specific conditions for higher vapor loss, transportation loss is also higher. The range normally lies between 2-15 psi. It is the sum of hydrocarbon vapor, water vapor and air.

BS & W (BASIC SEDIMENT AND WATER))

It is a measure of the amount of non hydrocarbons (sand, sediment etc) and water. A standard quantity of crude oil is taken in a calibrated tube using a centrifuge, the sediment are allowed to settle. The amount of sediments is directly read off the tube. The acceptable range of BS&W generally less than 0.5%.

ORGANIC THEORY OF ORIGIN OF PETROLEUM

There are two theories regarding the origin of petroleum

1. Inorganic Theory
2. Organic Theory

INORGANIC   THEORY

According to this theory petroleum  products orginated from the carbon available inside the mantle of the earth. Carbon reacted with water and hydrogen inside the earth in the presence of some metals that functioned as catalyst. This happened due to the high temperature existing at that time. Now this theory is more or less discarded and the organic theory is found accepted.

ORGANIC THEORY

Organic matter is the dead remains of plant and animal organisms. As these organisms died they went down to the shallow sea bed. Through millions of years rivers flowed down to these sea beds and were covered with mud and slit. Over a period of time they were covered with mud and slit and got buried deep and deeper. Once the organic matter got buried  below, they did not decay due to lack of contact with atmosphere.

CHEMISTRY
Oil and gas are made of a mixture of different hydrocarbons. As the name suggests these are large molecules made up of hydrogen atoms attached to a backbone of carbon.

PLANKTON
Most oil and gas starts life as microscopic plants and animals that live in the ocean.

BLOOMS
Today, most plankton can be found where deep ocean currents rise to the surface. This up willing water is rich in nutrients and causes the plankton to bloom.

ON THE SEA BED
When the plankton dies it rains down on sea bed to form an organic mush. If there are any animals on the sea bed these will feed on the organic particles.

BLACK SHALE
However, if there is no oxygen in the water then animals cannot survive and the organic mush accumulates. Where sediments contain more than 5% organic matter, it eventually forms a rock known as Black shale.

COOKING
As black shale is buried, it is heated. organic matter is first changed by the increase in temperature into kerosene, which is a solid form of hydrocarbon. around 90°c , it is changed in to a liquid state, which we call oil. around 150°c, it is changed into a gas. a rock that has produced oil and gas in this way is known as a source rock

MIGRATION
Hot oil and gas is less dense than the source rock in which it occurs Oil and gas migrate   upwards up through the rock in much the same way that theair bubbles of an underwater diver rise to the surface. The rising  oil and gas eventually gets trapped in pockets in the rock called reservoirs.

A,B,C SCANNING MODES

A SCAN

Ultrasonic testing can be done using various modes, A scan is most widely used among them,wich can be called as one of the common testing techniqes in manual ultrasonic testing.the reflected energy either from a defect or the back wall of a specimen are displayed as signals on the CRT display.
there are two axis on the flaw detector screen wich is x- axis and y- axis. the x-axis represents the time or distance where as the y-axis represents the signal amplitude or the energy of the returning echoes from the specimen.
In this system the size of a defect can be analysed by looking into the amplitude of the returning echoes and defect location can be understood by the positioning of the echoes on the time or distance base, and also type of the defect can be analysed by giving a lateral as well as swivel scan on the test material and thus it produces the corresponding shapes in echoes wich helps in easily identifying the type of defect.
Overall we can say that by this method you can get  size ,shape and depth of the defect using A-scan method.

B SCAN

The B-scan system gives us  a cross sectional view or end view of the test material under scan.here the  depth of the defects can its linear dimensions can be accurately evaluated.the time taken by the sound wave to travel is displayed on the y-axis and the position of the probe placement is shown on the x-axis of the display.

C SCAN 

This method gives us a plan view and also size of the total test specimen.the defects are shown as a contrasting areas on a printout wich is related to the probes movement over the surface.

MAGNETIC PARTICLE TESTING

It is the one of the most widely used NDT methods.This method is so fast and relatively easily as it requires least surface preparation when compared to other techniques.the magnetic particle examination method can be applied to detect crack and other defects at the surface and also sub-surface of the material under test, particularly ferromagnetic materials.for example- iron,cobalt and nickel.Types of defects that can be identified by this method are cracks,seams,cold shut,porosity,etc.

PRINCIPAL

This method is a combination of  NDT methods which are visual testing and magnetic flux leakage testing. The principal of this method is magnetic flux leakage or leakage in magnetic field or change in magnetic permeability

ADVANTAGE

1. This method is relatively faster than liquid penetrant testing for the surface defects
2. Indication at subsurface level can also be identified portable equipment's

DISADVANTAGE

1. De magnetization of a part is required after the test
2. We can apply this method only in ferrous material and cannot inspect Non ferrous materials such as aluminium ,stainless steel etc.

Introduction to NDT (Non Destructive Testing)

NDT means Non Destructive Testing. Normally we may use two different types of testing methods such as destructive testing as well as non destructive testing for a test material. Destructive testing means we must destroy that particular test material and detect whether some defect is there or not.  In this case we cannot use that material afterwards. So we are going for NDT. Here we are not doing any harm to the test material so that we may reuse it. NDT mainly follows two different standards.

·       American Standards (ASNT)

·       British Standards.

In NDT we are mainly dealing four different types of testing methods.

Ø Ultrasonic Testing (UT)

Ø Liquid Penetrant Testing (LPT)

Ø Magnetic Particle Testing (MPT)

Ø Radiographic Testing (RT) 

Ultrasonic Testing (UT)

We are mainly using the Ultrasonic sounds waves for the testing. This method is commonly used for finding out the internal discontinuities present inside a test material. The sound waves will passes through the test materials and produce an echo.

Liquid Penetrant Testing (LPT)

LPT is the technique used for finding out surface discontinuity by applying a Penetrant on the surface of the test specimen.

Magnetic Particle Testing (MPT)

MPT also used for finding out surface discontinuity by utilizing the test specimens magnetizing property.

Radiographic Testing (RT)

RT is used for finding out internal discontinuity such as porous, cracks, voids. etc. This is done by making use of electromagnetic waves. And an image will be produced on the radiographic film. By analyzing the film we are able to find out the defect.

What is circular magnetization and how do we do it ?

Circular Magnetization 

Circular magnetization id the process of creating circular magnetic fields .Circular magnetic fields are produced by passing current through the part or by placing the part in a strong circular magnet field . 

Methods to produce Circular electric field : 

1. A headshot on a wet horizontal  test unit and the use of prods are several common methods of injecting current in a part to produce a circular magnetic field
2. Placing parts on a central conductors carrying high current is another way to produce the field

HEAD SHOT METHOD 

The units have head and tail stocks (similar to a lathe) with electrical contact that the part can be clamped between.   A circular magnetic field is produced with direct magnetization. 

The tail stock can be moved and locked into place to accommodate parts of various lengths. 

Advanced reference : http://www.nrc.gov/docs/ML1214/ML12146A182.pdf