Ocean Pakistan Limited.
Production & Maintenance Unit.
PRODUCTION AREA REPORT OF DHURNAL
SUBMITTED BY:
Abdullah bin Masood (EME College, NUST)
SUBMITTED TO:
Maintenance Supervisors: Field Superintendent:
Zeeshan Shafiq Tanveer Ahmad
Tariq Mehmood Chaudhary Shafique
PRODUCTION OF DHURNAL OIL FIELD
- Introduction of OPL:
Ocean Pakistan Limited (OPL) formerly Orient Petroleum International Inc., is an Oil and Gas Exploration and Production Company registered in the Cayman Islands and successor-in-interest to Occidental of Pakistan, Inc. that began petroleum exploration in Pakistan in 1979. OPL is a prudent, low-cost and efficient enterprise poised to play a leading role for oil and gas exploration in Pakistan.
OPL is led by a dedicated professional Management team and staff. The Company operates Dhurnal, Bangali and Ratana Development and Production (D & P) Leases together with Sakhi Sarwar, Marwat and Harnai South Exploration.
OPL has a track record of achieving growth and increasing asset base value of the Company through development of discovered assets, new acquisitions and actively pursuing high potential deeper prospects within its development leases. - Introduction of Dhurnal field:
Dhurnal Oilfield is located 60 km Southwest of Islamabad in the Potwar Plateau, Upper Indus Basin. It is currently producing about 106 BOPD and 0.5 Mmscfd of gas.
Dhurnal was the largest oil-producing field in Pakistan with peak production of 20,162 BOPD in 1988.
In 2009, OPL carried out 3D Seismic Survey and our recent evaluation based on interpretation of this seismic data has identified new remaining potential in the lease area. Company will be embarking to tap this potential which will help us to achieve the objective to increase production and reserves of this asset.
Dhurnal field has produced around 50.5 MMbbls of Oil and 130.9 BCF of Gas as of October 31, 2014.
- Health, Safety, Environment and Quality:
OPL is committed to providing a safe and healthy workplace and ensuring that all business activities are conducted in a manner that protects the personnel and environment. This is the Charter OPL follows through its policy and is achieved by its stakeholders at all locations by adhering to the principles which lead to controlling hazards and reducing risks to acceptable levels, reduction of waste, protection of environment, conservation of resources, compliance with applicable quality and industry standards, codes, HSEQ legislation, delegation and ownership of Quality and Safety at all levels of the organization.
Our proactive approach towards prevention and intolerance to the conditions that contribute to incidents and injuries has led to continual improvement of HSEQ performance and improvement in LTI. - Construction of well:
Well is not like ordinary water well but it consist of proper construction which is called CHRISTMAS TREE.
Christmas tree is shown as:
Christmas tree holistically consist of several appendages that eject the oil from the deepest of sub surface of earth behind the layers of water and gas.
The several valves through which this apparatus work consist of:
- Pressure Gauge
- Swap valve
- Wings Valves
- ESV Valve
- Choke Valves
- High low Pilot Valves
- Parameters Valves
- Chemical Injection Valve
- Upper Master Valve
- Lower Master Valve
- Annulus Valve
- Fence Valve
Detail of Wellhead:
To completely understand the working of well we must know that the how different valves work and their correlation with each other.
• Pressure Gauge:
It is mounted on the top of Christmas tree and it tells us about the well head pressure. It is very vital part of this construction because it keeps view of pressure and if that pressure exceeds the critical limit it automatically open the extra fluid coming from well to flare.
• Swab Valve:
Swab valve is the highly critical because the job on the well can be performed by this valve only. As the crude oil is continuously coming out of the well it is often happen that the underground deeply rooted pipeline system clogged with externalities like pebbles. Because of this the pressure coming from well reduces and production does not comes to set point. For this different chemicals are injected in Swap Valve by closing side wing valves through tubes and remove the blockade in passage of crude oil.
• Wing Valves:
Wings valves are usually hand operated manually. These are just use to manually control the flow of liquid in any case. Wings valves does not provide us the proper amount of flow controlled or that transgress. Or in case of job performance it is just used to close the side flow of crude oil.
• Upper and Lower Master Valve:
Upper and Lower master valve is used in the case of maintenance problem if any problem occurs in the Christmas tree. As crude oil is continuously coming out, so in that case we close the lines below upper and lower master by closing these valves. First of all lower master is closed in case if flow leakage occurs in lower master we close upper master as well to completely seal the well.
• Annulus:
Sometimes if the reservoir of the well is so below and deplete with oil and gas reserves we have to artificially pump the oil from well through injection water or gas injection. Annulus is the space between the narrow internal tube through which the oil is coming out and having pores in bottom and casing encapsulating the tube. Through this space we inject gas externally and pump oil out of reserves.
• Choke:
Choke valve is very essential to the knowhow of the flow coming from well (flowrate) and adjust the calculated amount of crude coming out of well according to our saving and processing capacity of our plant or adjusting overflow.
• Emergency Shutdown Valve:
ESV or emergency shutdown valve is after the wing valve in Christmas tree .ESV in pneumatic (air pressure controlled) which adjust itself using air .ESV is directly related to High Low Pilot.
• High Low Pilot:
High low pilot is gauge to which maximum and minimum value of pressure and temperature is give.it means if any one of these two parameters goes beyond max value and below minimum value it will automatically shut down the ESV .Both ESV and High Low Pilot directly related to each other.
• Chemical Cylinder:
Chemical cylinder is situated near the pressure and temperature parameters of out coming crude oil and injection gas. It uses a positive displacement pump or PD pump to pump the corrosion inhibitor in the pipelines to protect these from corrosion.
• Fence Valve:
If we start a well which is shut down for some time here the important fence valve is used. Initially the crude oil coming from well may be consisting of many impurities and we do not send it into main line but divert it to flare line through fence valve to check characteristics of crude.
Another advantage is to use it as substitute of main line in case deterioration of mainline due to some maintenance issue. We convert the flow from well through fence into mainline.
- Wells of Dhurnal Oil Field:
Dhurnal oil field consist of 7 wells in which D-3, D-7, and D-4 are closed now due to low reservoir and poor maintenance.
Wells are discussed below:
o D-1:
D-1 is gas injection well in which gas is injected through annulus to the pores of internal narrow tube of oil at a pressure of 2840psi and oil pressure coming out of well is about 760psi.it is single tubing well. Tubes construction of wells include 4inch internal narrow tube through which oil is coming outside it 9inch tube then 13inch tube casing then 20 inch most external tubing.
o D-2:
D-2 is similar as D-1 except the difference of water injection instead of gas injection. For this purpose a jet pump is used there to force the crude out of reservoir .Venturi effect occurs in jet pump to create suction to pull the water out of foot valve to main stream pipe. Foot valve consist of stainer to remove impurities from crude to certain extent.
o D-3:
D-3 is open but no flow is coming from this well. This well is also Christmas tree type.
o D-4:
D-4 well is for water injection purposes but at this time it is closed.
o D-5:
D-5 well is in working condition but now only water is coming. There is no gas and oil coming until now.
o D-6:
D-6 has same Christmas tree construction and working as D-1.the main difference here is the double tubing for crude ejection because at the spot where D-6 is located have two reservoirs one is deep and other is short, so we have to use dual tubing and dual cycle of Christmas tree to force crude out of valve. It is also gas injection well as D-1.
Coil tubing and Nitrogen pumping job is done on D-6 to remove water static head from the well.
D-7:
D-7 is mainly for water injection purposes. It is not used to get flow of crude oil, gas and water.
- Schematic working
Main parts for the processing of crude oil, gas and produced water in Dhurnal oil field are listed below:
- Well
- Well Manifold
- Separator/Disalter
- Crude oil cycle
- Gas processing cycle
- Produced water cycle
- Water injection plant
o Well:
Well consist of Christmas tree discussed before to pull the mixture of well through tubing’s of different diameter mentioned above to the main well manifold.
o Well Manifold:
Well manifold is shown as:
Well manifold is a junction on which flow from different wells gather
To form a main stream. Here flow mixture is coming from all the wells. Well Manifold consists of Orbit valves to control the path of flow from well by diverting any line to desire disalter/separator.
If we want to work on any line of separator, then we close supply to that separator and direct all flow mixture to other separator.
PSV (Pressure safety valve): There is a pressure safety valve in manifold area. If pressure in tubes is high then it will reduce the extra pressure from tubes and will direct it to flare.
Rupture Disc: there is a rupture disc in one of the manifold tubes between flinches. When we want oil mixture to be directed to flare then we put that mixture in rupture disc tube. Also if pressure in tubes is high then rupture disc is used to get rid of that pressure. Rupture disc is a disc between two tubes. When pressure is high in tube then this rupture disc break and all the flow is directed towards flare.
o Separator/Disalter:
Separator is a device which separates the coming flow from wells into gas, crude oil and produced water. In dhurnal field, main separator is out of order so we are using disalters as separators. Disalters serve the same purpose as the separators i.e. to separate the coming flow into gas, crude oil and produced water.
In dhurnal field, 2 disalters are being used. We can send coming flow from different wells to any disalter (separator). Different control valves are installed at separator section to control the flow and level of crude oil, gas and produced water.
Separator is shown as:
Disalters, which are used in dhurnal field, are shown as:
• Working of Separator:
Separator is a 3 phase device. Flow enters from one side of separator and strike a plate. As a result crude oil and water go to bottom of the separator and gas goes up due to gravity.
GAS: Gas is taken from the upside of the separator. Before going out of the separator, gas is passed through Demist pad. It removes the moisture particles from the gas.
Water: As density of water is quite high, it goes to the downside of the separator and is taken out.
Crude Oil: Density of crude oil is lower than water so it does not go to the full bottom of separator instead it stay in the medium of separator. There is an interface between crude oil and water which prevents them from mixing. We have to prevent crude oil from swirls in separator so crude oil is passed through different stages. As a result swirls are not created in crude oil.
There is a weir plate in separator. As flow is coming in separator then level of oil also keep increasing. Oil then cross this weir plate and goes to the bottom of separator is taken out from the separator.
• Control Valves:
There are control valves in separator section which control the flow level of crude oil and produced water and pressure of gas.
PCV: These are called pressure controlled valves. They are used to control pressure of gas in separator.
LCV: These are called level controlled valves. They are used to control level of produced water and crude oil in separators.
Other controls valves are also installed in separator section.
• Readings:
Plant operators note reading after the separator from graphs after every 2 hours. From that graph they note the pressure and temperature of crude oil and gas. They also note differential pressure in case of gas. After inserting these graph values in computer they get the amount of crude oil and gas which is being produced from the well.
Crude oil and water is measured in barrels.
Gas is measured in mmscfd.
Following Barton charts are used for reading calculation.
- Cycles after Separation:
After leaving separator/disalter three cycles are formed of these water, gas and crude oil which are discussed below:
- CRUDE CYCLE:
Crude oil leaving disalter/Separator goes to crude oil tanks of 10000bbls capacity by tubes having brown color coding. From this tank this crude oil is sent to oil refineries.
• Crude Oil Tanks:
There are total 3 crude oil storage tanks. Out of these 3, 2 are used for crude oil storage and remaining 1 is used for water (condensate) storage which is coming from Scrubble. Level of crude oil storage tanks is checked regularly.
In crude oil storage tanks a specific pressure is achieved. If pressure is too low in tank, vacuum will be created and if pressure is high than specific limit then tank can explode.
Blanket Gas: we have achieved specific pressure in tanks with help of blanket gas which is the natural gas coming from the wells. With blanket gas system there is a control valve too. This control valve automatically closes when there is required pressure in tank.
Breather: there is a breather on storage tanks. If pressure is high in tank then this breather removes that extra pressure from tank.
Crude oil tanks are shown as:
- GAS CYCLE:
Gas after leaving separator is passed through different processes. After being processed, gas is divided into 2 parts.
i. Gas is sent to CNG compressors for injection in the wells.
ii. Remaining gas is then sold to E-gas Company.
Gas processing cycle consist of the following units:
o Gas cooling Fan/Gas Cooler:
Gas cooling fan is shown as:
Gas leaving the separator in yellow color coding tubing passes through cooling fan to cool the gas. To run the fan, a motor is connected to fan through pulley.
o Scrubble:
Scrubble is shown as:
Scrubble is a unit in which moisture or condensate of gas is removed by passing it into tank in which as water is heavy it settles down and we remove this condensate and store in storage tank.
o Glycol unit:
After passing through Scrubble, gas is passed through glycol unit in which glycol is showered from above of the tank and gas is inserted from bottom. In this process, moisture is absorbed by glycol.
In Dhurnal field, we are not using this glycol unit. So, the gas is passed to next processes without entering into glycol unit.
o Distribution of Gas:
After passing through all these processes, gas is distributed as:
i. Gas is sent to CNG compressors for injection in the wells.
ii. Gas is sent to generator area as a fuel of Waukesha engine (740 KW) which is used to generate electricity for camp area and to run CNG compressors.
iii. Gas is also sent to mess of field.
iv. Remaining gas is then sold to E-gas Company.
- WATER CYCLE:
The water coming along with crude and gas mixture is very hazardous and cannot be drained to any open place because it is salty water and can causes burn and injuries and for plants and agriculture it is very dangerous because it destroys crops and production.so this water is circulated to water injection plant and then dumped into the D-5 to save local community.
Water injection plant:
Water injection plant consist of following processes:
o Degaser
o Cooling fan
o Chemical mixing
o Storage tank-1
o Up flow filter
o storage tank-2
o Media filter
o Booster Pump
o Degaser:
First of all water enter into the degaser where the gases like butane are removed from produced water. These gases are entrapped into water and are eliminated in this process.
o Cooling Fan:
After passing through degaser water enters into cooing fan to cool itself from hotness it have.
This cooling fan is shown as:
o Chemical Mixing:
After passing through cooling fan some chemicals are injected in this water to save our lines from corrosion and other effects.
Following chemicals are injected here:
- Citric acid.
- Corrosion inhibitor.
o Storage tank-1:
After passing from cooler, water is stored into storage tank where it takes some time to stay it is because this time is given to water so that particles and chemicals in it settle down or precipitate. Monthly biocide of these storage tanks is taken to kill any bacteria in water.
o Up flow Filter:
In up flow filter the process happening is called SKIMMING. This process removes the particles of oil in water. This tank consist of suction and discharge section.
The up flow filter is cleaned through backwash to remove waste through water and gas.
o Media filter:
Media filter is not currently working because it was used when fresh water from river used to dump into well.
o Storage tank-2:
As storage tank-1, storage tank-2 also provide staying time to water for the settling of chemicals by storing into it.
o Booster pump:
There are always 2 booster pumps in this area. 1 is operational and other is used as a backup.
These booster pumps are centrifugal pumps which are being run from induction motor.
These booster pumps inject this produced water into our desired well, normally this well is D-5.
A 3rd booster pump is also kept as backup which is positive displacement type.
Booster pumps are shown as:
Water storage tanks are shown as:
- Flare System:
If pressure is high of system that control valves will direct all the extra pressure of oil or gas to the flare system. Any unwanted gases or chemicals are constantly being removed to flare.
All valves are connected with flare lines to direct flow or extra pressure gases to flare.
- CNG Compressors:
There are total of 4 CNG compressors in the field. They are used to create pressure up to 3000 psi to inject compressed gas into the wells. These CNG compressors are of E-gas Company and are maintained by workers of E-gas. These CNG compressors are 4 stage compressors. All of these 4 compressors are same in design and working.
Compressor consists of following parts:
- 4 stages
- Gas filter
- Heat exchanger(QTY:4)
- Oil Pump
- Cooling towers(QTY:4)
- Oil separator
- Main Motor
- Pressure Control value.
- Pressure gauges(QTY:6)
- Actuator valve
• Working of CNG compressors:
Compressor is used to compress the gas coming from the well with high pressure.
The schematic working of compressor is expressed below:
First of all the gas coming from source is adjusted to 10-20 bar pressure immediately after starting the compressor to run the compressor through pressure controller otherwise source pressure is reduced. For indication of pressure coming from well a pressure gauge is used.
Actuator valve which is installed after the pressure gauge is air controlled to close the source gas in case of high pressure.
After Trans passing through actuator gas enters the first stage of compressor. Here the gas is compressed through piston/plunger arrangement up to a specific value which is set by manufacturer. The value is 5-10 bar.
As the compressed gas is heated by to and fro motion of piston/plunger, so here need is to cool the gas. After exit from first stage the gas enters into heat exchanger for transfer of its heat to oil/water..
Then compressed gas enters into second stage for further compression here the pressure is increased up to 40 bar.
Similar cycle happens after leaving from second stage and gas enters into third stage where pressure increases up to 60 bar.
Similarly after leaving 3rd stage into final stage where pressure is increased up to 230 bar.
After all these stages the gas enters into oil separator to remove oil particles from gas.
Finally gas is cooled in cooling tower then injected into well.
A motor is used to drive the compressor.
Oil pump is used to pump lubricating oil to remove heat from whole apparatus.
- CNG compressors are shown below.
- Laboratory:
Laboratory is an important part of oil and gas industry. In laboratory,
We take samples of flow which is coming from well. This flow includes crude oil, gas and produced water. Then we analyze them through different tests. On base of results of those tests, we calculate different values and properties of crude oil, gas and produced water. Normally we do this analysis twice per week.
Also, we add different chemicals in tanks and pipes of flow for their safety and maintenance.
• Tests of Crude oil, Gas and Water:
First we take sample of crude oil, gas and produced water which is coming from the wells. After taking samples, we pass these samples from different tests and calculate different values and percentage of quantities.
GAS: In gas, after taking and analyzing sample we check quantity (in percentage) of methane, ethane, H2S, CO2 and other components of gas. After this we calculate calorific value of gas.
Crude Oil: After taking and analyzing sample of crude oil, we check its
API Gravity.
Percentage of salt.
Percentage of water.
BS & W.
Vapor Pressure.
Produced Water: after taking and analyzing sample of water, we check its
PH.
Salt (chlorides).
TDS (Total dissolve salts).
TSS (Total suspended solids).
• Addition of Chemicals:
We add different chemicals in tanks and pipes during flow for their safety and maintenance.
Following chemicals are added during different phases.
Corrosion inhibitor.
Scale inhibitor.
Corrosion inhibitor for gas.
Citric acid.
We also do monthly biocide of tank to kill bacteria.
o Process:
Process of chemical injection is as:
i. First we add 2 chemicals in tubes at the start of well. This chemical injection is carried out with help of Pogo Pump. These 2 chemicals are:
Corrosion inhibitor.
Scale inhibitor.
These chemicals are injected to save tubes from corrosion which happens due to flow.
ii. When gas is taken out of the separator section then “corrosion inhibitor for gas” is injected in the lines of gas to save lines from corrosion.
iii. Produced water goes to degaser then to cooling fan and then it enters into first storage tank. We inject chemicals in water before it enters into first storage tank. Chemical’s injection is as:
o First we add citric acid into water.
o Here we add corrosion inhibitor again because the previous corrosion inhibitor is finished by reaching at water storage tank.
o In this water bacteria are present. To kill those bacteria, we do biocide of storage tank.
- Fire Water Pumps:
Fire water pump is used to supply water to all hydrants in the field and camp area. We use those hydrants if there is fire on field or camp or if there is any emergency. The hydrants are installed in different and important locations at the field and camp with red color as their indication. When we start these hydrants, water with high pressure comes out and we can deal with emergency.
• Locations of Fire Water Pumps:
There are total of 3 fire water pumps in Dhurnal Field. 1 is used at a time and others are used as a backup if there is any fault in other fire water pumps.
i. 1 fire water pump is installed at the front of production camp. This pump is brought from Bangali field of OPL. This pump takes suction from water tank.
ii. 2nd fire water pump is installed in front of manifold area. This pump takes its suction from fire water pump pit.
iii. 3rd fire water pump is installed in front of manifold area with 2nd fire water pump. This pump also takes it suction from fire water pump pit.
• Engine of Fire Water Pumps:
With each fire water pump, diesel engine is coupled. This diesel engine gives rotation to pump and we are then enable to make use of fire water pump. Maintenance of these engines is done on regularly basics.
• Working of Fire Water Pumps:
All of these fire water pumps are centrifugal pumps which take suction from their source and pump this water to all the hydrants through water tubes.
These fire water pumps operate at a specific pressure but first we have to maintain such pressure in water tubes that these pumps don’t start every time. For this purpose we use Jockey Pump.
Jockey Pump:
There is a jockey pump in fire water pump area. This jockey pump is there to maintain pressure in water tubes up to 180 Psi. Jockey pump maintains this pressure by supplying water to tubes after sometime. When fire water pump starts then this jockey pump is stopped.
We have 2 fire water pumps together in front of manifold area. One of them operates at 150 Psi and other operates at 120 Psi.
Now if we open valve of a hydrant, water will come out of that hydrant and pressure in water tubes will drop and as the pressure drops fire water pump which operates at 150 psi will start operating and will supply water to all the tubes and hydrants.
If because of some reason fire water pump at 150 Psi does not operate then fire water pump at 120 Psi will operate and do its work.
Fire water pumps can be set to start automatically but we will have to close them manually.
• Fire Water Pump Pit:
There is a fire water pump pit with 2 fire water pumps. Fire water pumps take suction from this pit and discharge it into all the hydrants through tubes.
Fire water pump pit is filled with water. Source of this water is Swan River and rain water. This fire water pump pit is shown below.
- Oil Pit:
There is an oil pit on back side of 2 fire water pumps. In this oil pit syphon effect occurs.
Oil and water from all the leakages are sent to this oil pit. In this oil pit mixture of oil and water comes. Then according to gravity effect, water goes to the bottom of pit because its density is high and oil stays above water due to its low density than water.
As mixture of oil and water keep coming, level of this mixture keep rising. Oil is on top of the mixture in oil pit, we then recover this oil with recovery pump and sent it back to separator. After being separated, pure crude oil is sent to crude oil tanks.
Water keeps getting out of the pit as the level of mixture increase.
It is shown in following picture:
- Generator Area:
There are total of 5 generators in production area. Out of these 5 generators 4 are placed in generator area and 1 is placed near production camp.
These generators are of flowing companies and power.
i. Waukesha (740 KW) Gas/petrol engine.
ii. Caterpillar (400 KW) Diesel engine.
iii. Caterpillar (275 KW) Diesel engine.
iv. Cummins (250 KW) Diesel engine.
v. Cummins (200 KW) Diesel engine.
At this time, Waukesha (740 KW) is being used for power generation in the field. We are also running 1 CNG compressor with this engine. We use gas as a fuel for Waukesha engine.
Caterpillar (275 KW) diesel engine is used as a backup of Waukesha engine for power supply.
Caterpillar (400 KW) is working now and is used to run 1 CNG compressor.
Cummins (250 KW) and Cummins (200 KW) are under maintenance right now.
- JOB PERFORMANCE AT D-6
Coil tubing and nitrogen pumping job is done on D-6 by SPRINT services company to lift static head of water column from well.
Here the essential units for the chemical and nitrogen pumping are:
i. Coil Tubing
ii. Injector
iii. BOP
iv. Nitrogen Tank
v. Nitrogen Pumping Unit
vi. Chemical Mixing Tank
vii. Chemical Pumping Unit
viii. Chemical storage tank
The detailed description of these units is given below:
COIL TUBING:
Coil tubing is vital and most critical equipment of the whole job performance. Coil tubing is totally hollow from inside through which mixture of chemicals according to compatibility of material of well and nitrogen is pumped into well till the tubing of well end in deepness. As tubing can cause havoc in case of any mishandling, so tubing is properly lifted and descended into well through proper equipment and effective controlling through control unit.to prevent the coil from hazardous H2S (20ppm) different chemicals are sprayed on coil tubing before sending into well as well as mixture of chemicals used inside well to save it from dangerous environment which can cause leakage and suspension of coil tubing.
The most critical factors in handling and managing the coil tubing through control unit depends upon:
Weight: 1.8 lb/ft. means 37,800 lb. or 17145.79 kg.
Length: 21000ft here in this case coil goes as below as 11000ft.
Material: high carbon steel.
Testing of Coil
Testing is very necessary before using coil tubing in real time problems.
Differential Pressure : 14000psi
Tensile : 68000lb
Injector:
Injector is basic driving component of coil into the well and out of well. Injector is held stationary while doing the job by a crane right above the well swap valve through which the coil is injected to well.
Injector based on chain and gripping block mechanism. On both side of coil tubing in injector there are chains having gripper block ahead of them revolving continuously to inject or push the coil into well with the help of gripper block which grab it with much force.
Behind the upper part of injector there is a Stripper in which the pressure of well coming out is compensated or reduced by using a piston, carbon seal through which the coil is Trans passing. The pressure coming from well push the coil upward to prevent the whole apparatus by piston pushes the carbon seal upward as the upper part is sealed so seal expands under this pressure and protect the unit.
BOP:
Blow out protection mechanism is safeguard for the whole job apparatus. It consist of 4 valves adjusted in two arm with wing valves to control. By standard there are 4 arms.
These are given below:
Blind
Shear
Pipe
Slip
In case any chemical blast in coil tubing while job performance or any leakage in tubing case upheave enormous pressure from the well as well as tubing which in result very dangerous to workers , environment and local community.to prevent this catastrophe we use blind valve to immediately clamp it .
The only purpose of shear valve is to cut the pipe below it.
Pipe valve is used to completely seal the whole process in case of any disagreement between company and service provider to avoid from any over cost and waste of energy and material.
Slip valve is used to completely squeeze the coil in case of any damage to avoid jerking weight and vibration of coil under its weight and pressure.
Blind and pipe are upward and work together.
Pipe and shear are downward and work in compliance.
Perforation:
Perforation is a process in the formation/reserve of oil through which the tubing in injected into the formation having explosives. These tubes having pores in it. Before performing job this procedure is followed. Then an electric spark is sent into formation and then explosion happens and eliminate all debris and pebbles to clean it. Other methods like pressure and nitrogen spraying also used in perforation instead of electric spark.
Formation Water:
In formation the water is used is not normal water but is brine water compatible with brine in liquid static head of column so that no mixing of brine happens from high concentration into lower due to difference in brine concentration.
Nitrogen tank:
The process begins with the filling of nitrogen tank by external supplier. The nitrogen tank consist of internal and external vessel and having space between them. As nitrogen is very cold having temperature -320C.two lines from nitrogen tank emerge one is into nitrogen pumping unit and second is return of hot nitrogen gas to tank with lubrication of nitrogen itself.
Nitrogen pumping unit:
Line of nitrogen coming into pumping unit is firstly compressed with centrifugal pump to create suction for positive displacement pump having plungers and hydraulic system. Next to C pump is PD pump to create enormous pressure as the system is hydraulic much heat is generated into system. This heat is compensated by using of coolant for lubrication in heat exchanger. As a result of this coolant becomes hot and comes into chamber where compressed liquid nitrogen and coolant mixes and liquid nitrogen changes into gas.
After leaving nitrogen pumping unit lines having nitrogen is accompanied with SLSR (slow line safety resistor).this is very vital because in case of explosion it resist the havoc which otherwise cause devastation because it have pressure of 15k psi.as bullet having pressure of only 350 psi imagine!
Chemical mixing tank:
As chemical is heavy than water the basic purpose of chemical mixing tank is to provide swirling motion of different chemicals and water by providing that kind of swinging tubes. We inject all these from above bottom and it goes through tubing and then C pump which is run by engine to pass to tank and pumping unit.
Chemical storage tank:
Its purpose is just to store the chemicals having different composition.
Chemical pumping unit:
Pumping unit consist of engine and transmission box and then to PD to coil tubing.
Maintenance Unit:
With production unit, there is a maintenance unit In Dhurnal field. This maintenance unit is in charge of all the maintenance in Dhurnal field and Ratana.
Maintenance unit consist of 4 shops and is supervised by a Supervisor.
These 4 shops are as:
- Mechanical Shop:
Mechanical shop is the most important shop in maintenance unit. As most of the machinery in fields is mechanical so for their repairing and maintenance mechanical shop is used.
In Mechanical Shop, following task are done.
Troubleshooting of all the mechanical problems in the plant.
Preventive maintenance of different engines and compressors.
Over hauling of engines.
Checking leakages of different pumps and solve them.
Solving problems and issues relating to booster pumps.
Overall inspection of all the generators in the plant area and generators area and troubleshoot their problem if any.
Troubleshooting pogo pump which is used to inject chemicals in the tubes on start of well.
Solving problems of generators with weather ford’s engineers at D-2 well.
Carry different tests on mechanical equipments.
Solving fire water pump and engine problems (if any) on urgent basics.
Giving Greece regularly to well head.
Greece is given regularly to all the mechanical parts.
Automobile shop:
Automobile shop is under mechanical maintenance shop. All the vehicles of Dhurnal field and Ratana are maintained in this automobile shop at Dhurnal field.
In automobile shop following tasks are done:
Overall maintenance of all vehicles in dhurnal field and Ratana.
Cleaning of all vehicles in Dhurnal field and Ratana.
Changing filters of all vehicles.
Check hydraulic system of tractor which is used to cut grass on the field.
Changing pistons of engines of different vehicles.
Change batteries of different vehicles.
Ac Shop:
There are lot of air conditioners installed in different camps of field. Air conditioning shop is responsible for maintenance of those air conditioners.
Also new air conditioners are installed in different camps which are installed by AC technicians.Instrumentation Shop:
Instrumentation shop is an important shop in oil and gas industry. It is responsible for all the control and safety valves in Dhurnal and Ratana fields. Also calibration of different gauges is done by the instrument technicians.
In instrumentation Shop, following tasks are done.
Troubleshooting problems related to instrumentation in Dhurnal and Ratana fields.
Calibration of different gauges like pressure gauges, temperature gauges etc.
Check blanket gas system of crude oil storage tanks on monthly basics.
Check settings of emergency shutdown valves on monthly basics.
Calibrate chemical injector pumps and find problems (if any).
Calibration of different pressure switches and temperature switches.Electrical Shop:
Electrical shop is also an important shop in maintenance unit. Main tasks of electrical shop are listed below:
Routine maintenance of all electrical equipment.
Change of bearings of motors.
Solve electrical issues of generators.
Maintenance of underground cables and cable troy. Any fault in these cables is minimized after calculating the fault.
Preventive maintenance of main breakers and magnetic conductors.
Maintenance of generators and induction motors.
Cathodic protection of underground lines to prevent them from corrosion.
Maintenance of batteries.
Mercury blast lights are used by electrical department if we have to work at night.
Ratana Overview:
In Ratana there are four wells R1, R2, R3 and R4.Main production is coming from R4 well. From well, natural gas, condensate and produced water is coming.
Condensate include gasoline, petrol etc. Crude oil is not included in this mixture.
Separator:
Flow mixture from well goes to separator where (with the gravity effect) gas, condensate and water are separated. After separator there are different cycles of condensate and gas.
Condensate Cycle:
When condensate is separated from flow mixture it has some gases in it and we have to take out those gaseous particles. For this purpose we pass condensate through degasing boot and remove gas. Then we send this condensate to condensate storage tank and this extracted gas is sent back to gas cycle after being passed through boot gas compressor.
Gas Cycle:
Gases from separator goes to cooling fan first. After cooling fan, gas goes to storage tank. From here gas goes to amine plant where CO2 and H2S are removed from the gas. From here gas goes to cooling fan and then goes to glycol unit and its moisture is removed here. After this process this gas is sent to pol Meyal field.
Amine plant:
In amine plant, amine is showered on gas from top and it absorbs CO2 and H2S from the gas entering from bottom. Now we have to recover this amine for its further use. Rich amine (having H2S and CO2) is then sent to a tank where it is heated and H2S and CO2 (which it absorbed) are removed. Then it is sent for cooling process in heat exchanger and cooling fan where its temperature is decreased and is ready for further use.
Two Positive Displacement pumps are installed for pumping of amine in whole process. One is running and other is on backup.
Glycol Unit:
In glycol unit, glycol is showered on H2S free gas. This glycol absorbs its moisture. This glycol is then sent back for recycling.
Boot gas compressor:
There is one boot gas compressor in Ratana field which a basically two stage compressor.
This compressor is run by a gas engine.
Low pressure gas vapors in condensate are passed through this compressor and after increasing their pressure they are sent to main gas line.