LOGGING WHILE DRILLING (LWD)………………………………………………..15
MEASUREMENT WHILE DRILLING(MWD)………………………………..………20
I did my (Six Months) Industrial Training at Drillog Petro-Dynamics Limited in partial fulfillment for the award of a Bachelor’s degree in petroleum engineering. The (MWD) Engineers really helped me to know the practical applications of most theories studied in school.
This report therefore, only gives an insight into the training, exposures and experience gained during my attachment with the Safety department, Measuring While Drilling (MWD), Logging While Drilling Department, Gyro department, Workshop of PDL.
In 1990, DRILLOG PETRO-DYNAMICS LTD. was established by a blend of patriotic, dedicated and experienced oilfield specialists and successful industrialists. The oilfield specialists had worked in multinational oil companies.
As at May 1998, Drillog Petro-Dynamics Limited had successfully done 61 directional Drilling jobs for Shell, Snepco, Consolidated oil, Chevron, up to 45 steer able directional drilling and 4 horizontal directional drilling wells. In addition, 25 magnetic multishot surveys, 4 Gyroscopic and 13 Electronic multishot surveys, 59 Surface Read-Out Gyro Survey and many other jobs were successfully handled within nearly Eight Years of existence.
DRILLOG PETRO-DYNAMICS LTD has very strong technical support agreement with DRILLEX SYSTEM INC. USA and GYRODATA (UK) LIMITED and a retinue of the best technology and detailed training, Drillog Petro-Dynamics Ltd maintains a clear lead in service quality. It sticks to strict adherence to quality assurance and quality control procedure, both in field performance and technical maintenance.
Drillog Petro-Dynamics limited is proactive and future conscious hence it’s huge investment in a maintenance workshop with modern tool handling equipment.
This couples with a stock of new and most modern down hole motors, measurement while drilling equipment and other equipment. This gave PDL an edge over its competitors.
Rules and regulation governing the condition of services of staff was initiated to improve work efficiencies, such rules are procedures for maintenance ,safety, visitors, vendors,
appointment, criteria for assessment, confirmation, designation and other employment process.
You will be responsible for housekeeping in your work area in order to eliminate hazards, keep your workplace tidy.
Floors, steps, stairs and walkways will be kept clean and free from slippery substances, tripping hazards or other obstructions to the best extent possible.
Cargo handling materials such as slings, shackles etc. will be stored in designated areas.
Escape routes will not be restricted.
Maintain free access to safety equipment.
Waste bins must be used to collect rubbish.
At no time will any flammable material be stored or used in the workshop area or rig floor.
Paints and chemicals should be stored in appropriate containers and never stored to with other flammable liquids or gases.
Repair all faulty tools and put back in the store.
You have the obligation to stop an unsafe operation.
Horseplay is not permitted at the restricted areas such as workshop, stacked tool areas etc.
The use of Personal Protective Equipment (PPE) is mandatory for all restricted areas, all manual jobs and when lifting is taking place.
Loitering is prohibited for all employees, contractors, vendors/suppliers and visitors during mobilization and demobilization exercises except for those actively involved in these activities.
Inspect your tools before use.
Secure your tools when working at heights.
Clean and store tools on completion of task.
Use only knives with blade locking mechanism and cut away from the body.
Disconnect and shut off any energy supplies when tools are not being used.
Use only air driven portable tools in hazardous areas.
Always choose the right tools for specific job.
EXTRA EYE PROTECTION IS REQUIRED WHEN USING THESE TOOLS
Use goggles or face shield when changing tong dies.
Using a hammer and chisel.
Using a high-pressure wash-down gun.
Using scraping brush.
Wear safety glasses under face shield for added protection.
HOW TO AVOID STRUCK BY HAZARDS
Do not stand or walk below hoisted loads.
Prior to lifting, ensure the load is clear of all obstructions and any fastenings have been removed.
Respect HSE signs and barriers.
Avoid climbing on containers and stacked materials and never stand between loads and walls.
GENERAL SAFE WORKING PRACTICES
Immediately report any injuries.
Do not use compressed air or wash down gun to clean your clothes and do not aim it to your body.
Always have at least one hand onto the handrail at all times and do not carry any tools or equipment with both hands when going up/down a ladder.
Loose clothing must not be worn around machinery.
Gas lighters are not allowed.
PERSONAL PROTECTIVE EQUIPMENT (PPE)
Personal Protective Equipment (PPE) is the last line of defense against many occupational hazards as identify in the oil and gas industry today. A reasonable number of work related injuries today would have been prevented, if the right PPE were used. PPE is mandatory and it is there to save life and prevent occupational related injuries. Remember to identify the right PPE to use when planning a given task. It would be a good practice to always maintain your PPE and not abusing it.
Minimum PPE requirements for a given task:
Non-metallic hard hats.
Steel toe safety boots/shoes.
Safety goggles with side shields.
Ear muff/plug when in an area with noise level of 82 db and above.
Consult the material safety data sheets (MSDS) when working with hazardous materials for the appropriate PPE to use.
Nose mask or respiratory protection must be worn to protect one from airborne contaminants.
Use fall protection such as safety harness when working at height above 2 meters or 6 ft 7 inches.
Note: The HSE Officer or your Supervisors will provide Training in the correct use of PPE.
First Aid is the immediate and urgent care given by a person to another who has been injured or has been suddenly taken ill.
In case of serious injury or sudden illness, while waiting for help, give immediate attention to the following first aid priorities:
Effect a prompt rescue like remove an accident victim from water or from fire.
Ensure that the victim has an open airway and give mouth-to-mouth or mouth-to-nose artificial respiration, if necessary.
Control severe bleeding.
Give first aid for poisoning, or ingestion of harmful chemicals.
Once emergency measures have been taken to ensure the victim’s safety, the following procedures should be carried out:
Do not move a victim unless it is necessary for safety reasons. Keep the victim in the position best suited to his/her condition or injuries; do not let him/her get up or walk about.
Protect the victim from unnecessary manipulation and disturbance.
Avoid or overcome chilling by using blankets or covers, if available. If the victim is exposed to cold or dampness, place blankets or additional clothing over and under him/her.
Determine the injuries or cause for sudden illness. After immediate problems are under control:
Find out exactly what happened. Information may be obtained from the victim or from persons who were present and saw the accident, or saw the individual collapse in the case of sudden illness.
If the victim is unconscious and has no sign of external injury, try to obtain proper identification either from papers carried in billfold or purse, or from bystanders, so that relatives may be notified.
Examine the victim methodically but guided by the kind of accident or sudden illness and, needs of the situation.
Loosen constricting clothing but do not pull on the victim’s belt in case spinal injuries are present.
Open or remove clothing if necessary to expose a body part in order to make a more accurate check for injuries.
Note the victim’s general appearance, including skin discoloration and check all symptoms that may give a clue to the injury or sudden illness.
Check the victim’s pulse. If you cannot feel it at the wrist, check for a pulse f the carotid artery at the side of his neck.
Check if the victim is awake, in stupor or unconscious.
If the victim is unconscious, look for evidence of head injury. In a conscious person, look for paralysis of one side of the face or body. See if the victim shows evidence of a recent convulsion.
Check the expression of the victim’s eyes and the size of his pupils.
Examine the victim’s trunk and limbs for open and closed wounds or for signs of fractures.
Check the front of the victim’s neck to determine whether he/she is a laryngectomee.
If poisoning is suspected, check for stains or burns about the victim’s mouth and source of poisoning nearby, such as pills, medicine bottles, household chemicals or pesticides.
Apply emergency dressings, bandages, and splints.
Do not move the victim unless absolutely necessary.
Plan action according to the nature of the injury or sudden illness, the needs of the situation, and the availability of human and material resources.
Utilize proper first aid measures and specific techniques that, under the circumstances appear to be reasonably necessary.
Remain in charge until the victim can be turned over to qualified persons such as a physician, an ambulance crew, a rescue squad or a police officer or until the victim can take care of himself or can be placed in the care of the relatives.
Do not attempt to make a diagnosis of any sort or to discuss a victim’s condition with bystanders or reporters
BASIC FIRE FIGHTING AND PREVENTION:
Fire is a product of a chain chemical reaction between three elements namely oxygen, heat and fuel when combined in their proper range of concentration. Fire is the most devastating hazard of the workshops and the rig platform. Poor housekeeping most often causes fire and explosion could result from fire out break.
THE FIRE TRIANGLE
FIRE AND EXPLOSION PREVENTION
Poor housekeeping and wrong/bad equipment handling cause most fire incidents. The first step in preventing disastrous fire incidents includes:
Maintain a good housekeeping practice.
Eliminate the cause(s) of the fire.
Control and extinguish the fire when it occurs.
FIRE AND EXPLOSION IN THE WORK AREAS
Always keep the workshop environment tidy.
Floors should be swept and oil deposits cleaned where it exists.
Combustible materials should be kept away from wielding areas.
Avoid operating on combustible floors and walls.
Fire extinguishers should be stationed at strategic points in the workshop, must be on a hook at least 1.5 meters from the ground level, be accessible and visible.
Fire extinguishers should be refilled or replaced once discharged.
Fuel or flammable liquids should be stored in specified fire free areas.
Maintain good ventilation in the workshop; always keep doors and windows open and exits clear of obstacles.
Fire fighting drills have to be carried out monthly or at least once every quarter according to location requirement. Staff must be trained on the use of any new fire fighting equipment installed at any time.
Emergency procedures in the case of outbreak of fire must be displayed in the base and at locations along with a map indicating the location of fire extinguishers and muster points.
Qualified personnel must do electrical installations. Make sure equipment ratings are properly checked before connecting them to power supply.
Smoking is only allowed in designated areas.
Don’t tamper with the rig electrical power supply without permission from the rig electrician. Always crosscheck the supply with our own meter before connecting your equipment. Note: Improper connection causes sparks.
If you notice fire, call the rig Safety Officer immediately to switch on fire alarm and attack the fire with correct extinguisher if safe to do so.
THE FIRE ALARM AND EVACUATION PROCEDURE ON NOTICING FIRE
Raise alarm: Shout fire! Fire!! Fire!!! Also, sound the fire
Alarm and use public address system if available to tell people the area on fire.
Call: Radio or telephone personnel to call the fire
Service stations using the fire emergency numbers stating clearly location of fire.
Extinguish Fire: If only safe to do so. Use nearest available
equipment e.g. fire extinguisher or reel hose.
Evacuate building: Leave the building if unsafe to fight fire.
Shut the door after you (do not lock).
Go to the nearest assembly or muster point.
ON HEARING THE ALARM
Evacuate building: Switch off electrical appliances e.g. A/C, PC
Close door after you and if possible do not lock.
Leave building through nearest exit.
Mustering: Go to the nearest assembly/mustering point.
Take along your visitors/client.
Do not re-enter the building under any
Circumstance until the emergency is declared over.
HEALTH OF PERSONNEL:
All personnel must undergo a fully pre-employment medical check up by the company recommended Clinic. Field Personnel must have health certificate of fitness for offshore work.
Employees should maintain high hygienic standard to safeguard their good health and those of others.
At no time should an employee on duty:
Work under the influence of alcohol or un-prescribed drugs.
Suffer from communicable diseases.
Have any condition, which will impair their judgment or ability to carry out their duties efficiently and in safe manner.
Should any employee feel unwell at any time of operation, he/she should go and receive medical attention. If it is at locations, report to MEDIC in charge of the location immediately.
An emergency drill on fire is carried out regularly at least once every quarter to test employees’ preparedness, alertness and prompt response in emergency situations.
In an emergency situation, alarm is used to inform workers of impending danger. Alarms are responded to with strict attention because it is the only informant of impending dangerous situation.
LOGGING WHILE DRILLING (LWD)
The logging while drilling operations includes the recording of data from the respective formation being encountered while drilling operation is going on. These data collected provides the LWD Engineer information on the Drilling Efficiency, directional Surveying, formation evaluation and Geo steering. The LWD operation also helps the Engineer identify the Formation encountered (whether Sand, Shale, Liquid, Gas region) during the drilling operation. Equipment used in carrying out the LWD operation includes:
High speed central interface module (HCIM)
Dual gamma ray (DGR)
Electromagnetic wave resistivity (EWR)
Stabilized litho density (SLD)
Compensated thermal density (CTN)
Drill string Dynamic sensor (DDS)
Pressure while Drilling (PWD)
The Telemetry Systems
This is an equipment which serves as a media through which data could be transmitted from the down-hole sensors to the surface in real time. There are three types of Telemetry system
1. Negative mud pulse
2. Positive mud pulse
Negative mud pulser: This telemetry system is usually run at the top of the LWD tool string to achieve minimum bit-to-sensor spacing. The negative pulser is powered by a lithium battery.
Positive mud pulser: There are two types of positive mud pulsers:
1. Standard positive mud pulsers (DWD)
2. High-temperature positive mud pulsers (SOLAR).
The positive mud pulsers are usually Turbine powered.
The HCIM (High Speed Central Interface Module)
This HCIM is the Main controller of the FEWD (Formation Evaluation While Drilling) system. As the main controller, or bus master, the HCIM is responsible for polling the sensors for their data, storing data from the non-smart sensors, and formatting the data for real-time data transmission. Both negative pulse and positive pulse telemetry is available for real time transmission with the HCIM. Negative pulse telemetry utilizes the Smart driver Controller (SDC), while positive pulse telemetry utilizes the PCD-K and TM. The HCIM is also responsible for the supply of battery power to some of the sensors like the DGR, EWR and PWD. It serves as an intermediary between the sensors and the LWD engineer i.e. the LWD is able to communicate with the other LWD equipment (Sensors) down-hole through the HCIM.
The Directional Sensors measures the orientation of the LWD tools with respect to the earth’s magnetic and gravitational fields in order to compute the azimuth and inclination of the well-bore and indicate the gravity (high-side) and magnetic tool-face orientation of steerable drilling tools. There are three types of directional sensors:
1. PM (Position Monitor): This sensor is used in conjunction with the negative pulse telemetry systems.
2. PCD (Pressure Case Directional): This is a sensor used with the DWD positive pulse.
3. DM (Directional Module): This is a high temperature sensor and it is used with the SOLAR 175 standard positive telemetry system.
The DGR (Dual Gamma Ray)
The DGR sensor is made up of two opposed banks of Geiger-Muller tubes with two independent detector circuits. This redundant configuration provides two independent natural gamma ray logs. The count rates from the two detector banks are typically combined in order to optimize statistical precision. However, in the unusual event of failure of one detector bank, a corrected gamma ray log can be produced from the second bank. The Applications of the DGR include:
1. In well correlation
2. In Logging of record
3. In Directional Control
4. Helps in enhancing interpretation of wire-line logs
The EWR (Electromagnetic Wave Resistivity
The EWR is a state-of-the-art, high frequency induction resistivity sensor. This tool comprises four radio-frequency transmitters and a pair of receiver antennas. By measuring both the phase shift and attenuation from each of the four transmitter-receiver spacings, eight different resistivity curves with differing depths of investigation can be provided. The Applications of the EWR includes:
1. Resolving of thin sand beds surrounded by shale.
2. Making of deep measurements before invasion.
3. Improving identification of hydrocarbon/water contacts.
4. Detecting of movable hydrocarbons.
SLD (Stabilized Litho Density)
The SLD sensor comprises two gained-stabilized, 254-channel spectral scintillation detectors and a Cs 137 gamma ray source housed in a steel drill collar. Overlying the source and detectors is a special stabilizer blade containing three low-density windows. The stabilizer blade emulates the detector pad windows collimate the gamma rays and focus the measurement. The Operating Applications of the SLD include:
1. Rapid sampling for density-derived caliper
2. Bulk density
3. Photoelectric effect
4. Borehole standoff
5. Wire line-quality density measurements.
Note: In Drillog Petro-Dynamics, the modified form of the SLD is the ALD (Azimuthal Litho density).
CTN (Compensated Thermal Density)
The CTN sensor is a new slim hole neutron porosity tool designed for logging boreholes ranging from 5.875” to 6.5” in diameter. The CTN sensor can be combined with the slim hole EWR, DGR, SLD, and PWD sensors to provide “triple-combo” logging services slim holes. The CTN employs redundant banks of He3 neutron detector at both the near and far spacing added reliability.
The Operating Applications include
1. Porosity measurements
2. Hydrocarbon typing
3. Cased-hole logging
DDS (Drill string Dynamic Sensor):
The DDS sensor is a three-axis shock and vibration sensor whose electronics and accelerometers are mounted on the insert of the DGR sensor. Tri-axial accelerometers measure lateral, tensional, and longitudinal vibration. Average, peak, and instantaneous
acceleration data are recorded. Real time analysis of the data can be used to detect and identify common causes of damaging down-hole vibration, such as bit bounce, lateral shock, stick/slip and PCD bit whirl. The DDS sensor is run as an additional sensor on the negative pulser inside the gamma insert. It provides down-hole vibration information from three orthogonal accelerometers that can be used to prevent tool failures. High vibrations have been correlated to drill string failures and to the failure of the down-hole tools, such
as MWD tools. When high vibration loads are detected, drilling parameters (e.g. rpm, WOB) can be modified to reduce these vibrations and reduce the risk of tool failures.
PWD (Pressure While Drilling):
The PWD provides annular pressure, and temperature measurements. Annular pressure is transmitted in real time every 6 to 30 seconds and displayed as an equivalent mud weight. Pressure and temperature data are also at a more frequent sampling rate (as fast as every 2 seconds) and recovered at the end of each bit run. The data can be displayed as both depths based and time based logs to facilitate interpretation of drilling and non-drilling events.
PWD tools are compatible with both negative and positive pulser and electromagnetic telemetry systems.
Operational Applications include:
1. LOT, lost circulation
2. Flow/Kick detection
3. Hole cleaning and collapse
4. Monitor mud properties
5. Optimize drilling practices
6. Under balanced drilling
The LWD tools are being powered by the lithium battery; this battery is uniquely made for this purpose and should be handled with care. The Lithium battery is made with Lithium Thionyl; Chloride as the Electrolyte and Carbon as the Anode.
Components of the Lithium Battery:
Can: This houses the cell.
Electrolyte: Either Thionyl chloride or Sulfuryl Chloride. It is needed to conduct electricity.
Separator: It is needed to separate the Cathode from the Anode. It also allows ions pass freely while keeping cathode and anode apart.
Collector: Serve as a conduit, for collecting electrons from the positive terminal and sending electrons to the carbon cathode.
Cathode: Receive the by products of the reaction. It is made up of Carbon.
Anode: To oxidize (donate electrons), there by making electron flow possible. It is made up of Lithium.
MEASUREMENT WHILE DRILLING (MWD)
The Measurement While Drilling department (MWD) is a recent introduction to all drilling companies so far. The function of the department as the name implies, is to take data (readings) in the drilling well while the actual drilling is being carried out. Before the birth of this department, drilling work had to be halted or delayed at different stages in order to take the readings in the well. The new technologies used by the MWD department makes it very useful in terms of accuracy of readings and more importantly time conservation, which is a very important economical consideration in drilling of an oil well.
The chief components mainly required for evaluation in the MWD department are the Sand and Shale contents of the soil. Soil samples usually give readings of a sample having both sand and shale combinations in different proportions. This information enables the driller to know when he is approaching an oil reservoir or when he has deviated. Other readings taken include Magnetic Field Strength, Dip Angle and Azimuth.
THE MWD MODULES
The MWD makes use of special cylindrical tools referred to as the MWD modules. There are basically four types of MWD modules, they are:
The gamma ray tube.
The MWD modules are usually assembled together in different combination referred to as configuration. This assembly of MWD modules is referred to as the MWD Monel. The MWD Monel is introduced into the drill well through along with the mud motor on which it seats.
As it is not convenient to run a wire into the drill hole to supply electricity to the MWD Monel, the battery is used to supply the needed power to the system. The battery has a voltage of 28 - 29 volts. It is usually enclosed in a tube called the "bent Hosing".
The battery possesses a 6-pin 4-plug configuration at one end and a 4-pin 6-plug configuration at the other end. These two ends are referred to as the up hole and down hole ends respectively. There are two types of battery commonly in use they are the lithium battery and the alkaline battery. The lithium battery is generally preferred because of its durability (up to 200 hours).
The battery must be connected below the electronics, and up to two may be used at one for prolonged period of time if necessary.
The electronics is the control unit of the MWD tool. It is made up of three parts.
The thermometer is used to measure the variation of the temperature while drilling. They can withstand temperatures less than or equal to 150 degrees centigrade.
The accelerometer is used to measure the inclination while drilling. Where, inclination is defined as the angle of the tool with the vertical (or true north). The inclination is not constant.
The magnetometer is used to measure the dip angle, Magnetic field strength, magnetic tool face and gravity.
NOTE: The electronics contains 3 accelerometers and 3 magnetometers, which are placed in the x, y, and z-axes.
The Pulser sends information (data) up hole in the form of signals through pulses sent through the mud as a result of change in pressure. The MWD DRT decodes the pulses, which travel to the surface. They tell the conditions existing in the MWD at any point in time. The pulser consists of two parts; Pulser driver and Oil pulser
Pulser driver - This has two solenoids in it. When current passes through them it causes the solenoids to move apart and this motion pushes the puppet, which is in the oil pulser. When these solenoids move a certain distance apart, a force of attraction draws them back together again and this pulls the puppet. The pulling and holding interval of the solenoid is a function of the pulse width (usually preset). Puppet pulses should range from 0.98 to 1.5 on a dial.
Oil poppet - This is filled with incompressible oil that can withstand high pressures. The pressure has an electronic switch, which is sensitive to flow in the mud. Once there is a mudflow the electronics switch is activated and sends signals to the microprocessor in the electronics, which in turn sends current to the pulser driver.
THE GAMMA RAY TUBE
The gamma ray tube has a scintillating detector (it detects radioactivity in the formation) that is used to measure the "counts of radioactive substances" in the hole. Maximum gamma count is 150. The reading from the gamma is sent upwards to the depth encoder
The Interconnect Module
A device known as the interconnect module is used in the MWD department to join two modules together. It is usually placed in between two of any of the MWD modules (Pulser, Gamma, Battery or Electronics) in any configuration required to take reading from the drill hole. The interconnect passes signals by means of pulses through probes at the core of its shaft.
Other functions of the inter connect module include: Flexibility, centralization and shock absorption of the MWD monel.
INTERCONNECT MAKE – UP PARTS.
1. The interconnect shaft: This is the most vital part of the inter -connect. It is a cylindrical - like tube with pins and holes (plugs) on each end. The two ends of the interconnect are referred to as the up hole and down hole ends. The up hole end consist of 6 pins and 4 plugs, whereas the down hole end consists of 4 pins and 6 plugs. The alternate pins and plugs on both ends of the inter connect are linked together by probes running through the inter connect shaft.
2. The bomber: This is a padded shock resistant hollow casing used to house the inter connect shaft
3. The bow springs: The bow springs are usually four in number for every one interconnect module.
They are attached at equal distances apart around the interconnect bomber with pins.
4. Bow spring retainers: The bow spring retainers used to connect the bow springs firmly around the bomber.
5. Spacers: These are flat, circular components similar to the washer used with bolts and nuts except they are much larger. They are used to reduce the gap between the bow spring retainers and the compression springs, and hence making the interconnect set up more intact.
6. Compression springs: These are hard refractory steel springs mainly responsible for withstanding heavy shock.
7. Threaded rings: These are hollow cylindrical components made from copper, which have external threading. They enable the protectors to be screwed on.
8. O-rings: These are round rubber accessories which are placed on special grooves in the interconnect shaft. They ensure easy slipping on and off of other components along the interconnect shaft during assembly and dismantling. The O-rings are also used to fasten split rings to the interconnect shaft.
9. Split rings: These are semi-circular in nature. They are of different sizes and have external grooves. Two split rings each are connected on each side of the interconnect shaft in special slots and are held together by O-rings.
10. The protector: This is a round, copper cup-like housing used to protect the probes in the interconnect shaft during handling and transportation and also against foreign bodies such as water and mud. They have an internal threading which enables it to be screwed unto the inter connect via the threaded rings.
TROUBLE SHOOTING THE INTERCONNECT SHAFT.
It is important to the MWD technician that the inter connect is confirmed to be in a perfect working condition before it is carried out to the rig site. Tests are carried out on the interconnect shaft and these operations are referred to as troubleshooting. Two tests are usually carried out to test the interconnect shaft. They are: The Continuity Test and The Insulation Test
The Continuity Test
This test is usually carried out after the interconnect module has been dissembled and cleaned. Before reassembling, the inter connect is tested for a break between the down hole and up hole ends. The test carried out for this purpose is referred to as the continuity test.
1. The interconnect shaft is placed on two wooden (insulated) stands.
2. A module break out unit (MBU) is connected leading to the up- hole end of the inter connect. The lead cable has an alternate 4 pins, 6 plugs configuration to match the 6 pins, 4 hole configuration of the up hole end of the inter connect.
3. The down hole ends of the inter connect are connected to the return cable, leading it back to the MBU. The 6 pins, 4 holes configuration of the return cable matches the 4 pins, 6holes configuration of the down hole end of the inter connect.
4. The switches of the Module Break out Unit are all set to the break position.
5. A multi-meter is used to test for the flow of electrical current by connecting its positive and negative ends to the positive and negative outlets of the MBU. This operation is done ten times serially, for the 10 positive and 10 negative outlet holes of the MBU.
The beeping sound of the multi-meter indicates that there is a flow of current between the up hole and down hole (from +ve to -ve) ends of the inter connect when the circuit is closed. This inter connect shaft is in good working condition.
The Insulation Test:
The insulation test is carried out in order to test whether there is a bridge in the circuit between the probes in the interconnect shaft.
The set up is similar to that of continuity test except that the multi-meter is replaced with a type of resistor referred to as omega. The reading on the omega should read infinity to indicate the insulation between the probes.
1. Same as steps 1-4 above.
2. The omega is used to test each of the probes of the 10 probes of the interconnect shaft for a bridge in current by connection the Omega to the positive and negative ends to the positive and negative outlets of the MBU. This operation is done ten times serially, for the 10 positive and 10 negative outlet holes of the MBU.
MULE SHOE/MULE SHOE SUB:
The Muleshoe functions normally by employing the Helix to offer a guide for seating the MWD tool into a specific orientation to be able to measure the tool face
Orientation referenced to the tool face of the MWD probe. The software is also designed to allow the operator to measure any offset of the Muleshoe to the tool face of the bottom hole assembly.
Secondly, the Muleshoe also contains the main orifice into which the pulser main signal poppet projects into to create the pressure pulse. There are five different orifices sizes: 1.28”, 1.35”, 1.40”, 1.50”, 1.60” OD used in the 6.5” and 4.75” Muleshoe sleeves. The 3.5” Muleshoe sleeve has three options for orifice sizes: 1.21, 1/23” and 1.25” OD. The main orifices are easily changed on the job site to accommodate the various flows that may be encountered through the course of a job.
The Muleshoe subs are subs specially designed and cut to receive and anchor the Muleshoe sleeves. The subs are designed to match the mating threads of the collars being used. It is recommended that the subs be cut from a non-magnetic material to insure spacing from the magnetometers in the MWD tool.
DIRECTIONAL DRILLING (DD)
The Directional Drilling department is directly responsible for the actual drilling of the well. This department receives information from the MWD Department. The data used by this department include:
Azimuth - This is the angular distance of the well from the north.
Magnetic field strength - This is measured in Gauss. The value of the magnetic field strength should not exceed a reading of 32 by more or less than 0.05. That is, from 31.95 to 32.05.
Dip angle - this is the angle made by the magnetic north and the horizontal. It is fairly constant at a particular location.
Light side - this is a face of the mud motor, which is usually scubed along its entire length.
Tool face - This is the horizontal component of direction in which the tool faces (i.e. the direction the bit of the drill tool faces). It is useful in determining the angular position of the mud motor.
THE MUD MOTORS
The motors are the tools used for the drilling operation. It powers the drilling bit which actually bores the hole that would lead to the environment where the crude oil could be drilled. The mud motors used by the company were supplied by Drillex. Drillex positive displacement motors comprise of four major elements, from top to bottom include:
1. The By-pass valve Assembly
2. The Power Section
3. The Transmission Assembly
4. The output shaft/Bearing Assembly
The By-Pass valve:
The By-pass valve is used to fill the string when tripping in hole and to empty the sting when pulling out of the hole, thus avoiding a wet trip.
It is fitted above the power section in its own removable sub. The valve remains open until the pressure of the flowing drilling fluid exceeds the spring stiffness of the valve. The flow rate required to close the valve is below the minimum specified working flow rate of the motor.
The Power Section:
The power section converts the hydraulic fluid energy of the drilling fluid into mechanical horsepower. The mechanical horse power of a multi-lobe rotor/stator power section is the product of high output torque and slow rotational speed. The power section consists of the steel rotor and elastometer stator.
The transmission assembly as its name suggest, transmits the rotational speed and torque produced by the power section to the output shaft/Bearing assembly. The transmission must be capable of absorbing the downward thrust generated by the power section and allow the rotor to remain in the correct axial relationship with the stator.
Output Shaft/Bearing Assembly:
The output shaft is a rigidly constricted hollow steel component that is supported within motor casing by radial and thrust bearings. The majority of the drilling fluid passes through the center of the output shaft to the drill bit.
The thrust bearing are capable of accepting the downward force from the rotor and reactive force from the weight-on-bit which operates in the upward direction. The rapid support bearing consist of either an elastometer banded to a steel line running on a hard Chrome journal or tungsten carbide lined steel sleeve wear surfaces running against each other
Modern rigs make use of the rotary rigs to drill holes. In order to learn about the components that it takes to make a hole, it is convenient to divide them into four main systems. They are;
1. POWER SYSTEM.
Every rig makes use of powerful internal combustible engines as its prime power source. Rig engines today do not require gasoline as a fuel, but diesel. Also, rigs require more than one engine to provide the needed power.
Gas engines use spark plugs to ignite the fuel-air mixture in their combustion to produce power. On the other hand, diesel engines do not have spark plugs, instead the fuel-air mixture is ignited by heat that is generated inside the engine. Any time a gas is compressed its temperature rises such that if compressed enough, it gets hot enough to ignite. There fore, diesel engines are sometimes referred to as compression-ignition engines, while gas engines are referred to as spark-ignition engines.
A rig may have two to four engines depending on its size. All engines are used together to generate enough horsepower (up to 3000hp) to be transmitted to various components on the rig. Two common methods used to transfer power on the rig are:
Mechanical power transmission
Electrical power transmission
Mechanical Power Transmission:
In this method, engine power is sent to various parts of the rig by machinery such as belts and pulleys.
The power out put by the engines is compounded i.e. all the engines have to be compound together in order to act as one. To do this, a hydraulic coupling or torque converters are mounted to each engine. A shaft called an out put shaft is comes out of each hydraulic coupling, which turn due to engine power. The shafts are then mechanically linked together with pulleys and chains.
Electric Power Transmission:
The diesel-electric power is the dominant method used to drive most of today's rigs. Diesel engines drive large electric generators, which in turn produce electric power that is sent through cables to electric switch and control gears. From here the electricity goes through additional cables- that are attached directly - to the equipment involved.
The advantages of the electric power transmission over the mechanical power transmission are:
It eliminates the entire heavy, complicated compound and chain drive.
Alignment problems are done away with.
Engine noise for the crew is reduced as the engines can be placed far away from the rig floor.
2. HOISTING SYSTEM.
The hoisting system is made up of:
The draw works (Hoist).
The wire rope.
The crown block.
The traveling block
The mast (derrick).
The draw works: This consists of a revolving drum, around which the wire rope, called the drilling line is wrapped.
It also has a cat shaft on which the catheads are mounted.
It also has other cat shafts, clutches, chain- and -gear drives for speed and also, a main brake, which has the ability to stop the drum. The main brake is assisted by the auxiliary hydraulic brake or electric brake to help absorption caused by the heavy load.
The wire rope: This is common to the ordinary fiber rope except that as the name implies it is made up of steel wires. The sizes range from 1 1/8 to 1 1/2 inches in diameter. The wire rope is designed mainly to withstand heavy load encountered on the rig.
The crown lock and the traveling block: are sets of pulleys which work together to suspend the drilling string. The crown block is the larger of the two. The wire rope or drill line is reeled over each of them in turns several times over, this acts has the same effect several lines. The number of turns depends on the amount of weight that needs to be supported. A large hook, attached to the traveling block is also attached to the equipment for suspending the drill string.
Masts: These are long, elevated metal structures on which the weight of the mud pump, drill, workers etc. They are designed to withstand loads of 0.25 million to 1.5 million pounds and a wind load of 100 to 130 miles per hour.
3. ROTATING EQUIPMENT.
Rotating equipment from top to bottom consists of:
The Rotary table.
The Drill string and,
The swivel has a handle similar to the handle of a bucket, except it is much larger, which fits inside the hook at the bottom of the traveling block.
The swivel is remarkable because it:
Sustain the weight of the drill string.
Permit the string to rotate.
Affords a rotating pressure tight seal and passageway for the drill mud to be pumped down the inside of the drill string.
The Kelly is a square or hexagonal short piece of pipe attached immediately below the swivel. Like the swivel it is a unit through which drilling mud is pumped on its way to the bottom.
The reason the Kelly is four or six sided is that it serves as a way of transferring rotating motion to the rotary table. The Kelly sits inside a part of the rotary table called the Kelly bushing, which in turn sits inside another part of the rotary table called the master bushing. As the master bushing rotates, the Kelly bushing also rotates and since the Kelly mates with the Kelly bushing the Kelly rotates. And since the drill pipe is connected to the bottom of the Kelly, the pipe rotates as the Kelly rotates. The bit also rotates because it is attached to the drill string.
The Rotary table:
This is the rig floor either powered of the rig power system or its own electric motor. It comprises of several parts, which include the master bushing and he Kelly bushing. It also has a pair of slips accommodated in the master bushing.
A set of slips is a tapered device with strong teeth- like gripping element which, when placed around a drill pipe help to keep the pipe suspended in the hole when the Kelly is being disconnected.
The Drill string:
The drill string consists of the drill pipe and a special heavy walled pipe called the drill collars. Drill collars like drill pipes are tubes through which mud can be pumped.
Drill collars are heavier than the drill pipes and are put on the bottom part of the string to put weight on the bit. This weight presses down on the bit and supports its drilling.
A length of drill pipe is about 30 feet long. Each length of a drill pipe (joint) is threaded at both ends. One end is threaded internally and the other externally. The inside threaded end (the female end) is called the box and the outside threaded end (the male end) is called the pin. When pipe is made up the pin is stabbed into the box. The threaded ends are also referred to as the tool joints.
These are devices, which are actually responsible for the creation of the drill hole. The Bits possess teeth, which are responsible for the actual cutting or gourging out the soil formation. They also have passages drilled through them to allow the drilling fluids to exit.
4. CIRCULATION SYSTEM.
Drilling fluid -also called mud - is usually a mixture of water, clay, weighting material and a few chemicals. Sometimes oil is may be used instead of water, or a little oil is added to the water to give the mud certain desirable properties. Mud is important in that it is used to raise cuttings made by the drill bits to the surface for disposal and also for keeping underground pressures in check while drilling.
The mud pump takes in mud from the mud pit and sends it out a discharge line to a standpipe. The standpipe is a steel pipe mounted vertically on the leg of the mast or derrick. The mud is pumped up the standpipe and into a flexible, very strong reinforced rubber hose called the rotary hose or Kelly hose. The Kelly hose is connected to the swivel. The mud enters the swivel and goes down the Kelly, drill pipe and drill collars and exits at the bit. It then does a sharp u - turn and heads up the hole in the annulus. The annulus is the space between the outside of the drill pipe and the wall of the hole. Finally the mud leaves the hole through a steel pipe called the mud return line and falls over a vibrating screen like device called a shale shaker. The shale shaker screens out the cuttings and dumps them inside one of the reserve pits. On off -shore drill sites, the cuttings are put into a barge, to be transported for disposal at a land site.
The mud drains back into the mud pits and is recycled back down the hole by the mud pumps.
The circulation system is generally a closed one.
Auxiliary equipments are equipment used to ensure maintenance of the drilling mud. They are:
Agitators - These are installed on the mud pits and help to maintain a uniform mixture of liquids and solids in the mud.
Desilters and Desanders - These are used if any silt or sand formation is being drilled. This is because the shale shaker screen is not fine enough to very small particles.
Degasser - As the name implies, this is used to remove gases from the mud, thereby assuring desirable density - Gasses make the mud to be less dense.
Hopper - This is a large funnel - shaped piece of equipment used when adding solid materials like clay and barite to the pit.
Mud house - This is used for storage of sacks and mud materials, to keep the safe and dry until needed.
The students industrial work experience scheme (SIWES) should be recommended for all science and engineering students, since the theoretical knowledge of their course of study is not enough to help them in the demands of the dynamic technological industry, hence, they need exposure to be abreast with the latest technological innovations in the industry.
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