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Drilling Engineering

*The report detailed below is a Summer Training Report in Drilling Engineering Submitted by Amir RIAZ on 27th December 1997 for the course PETE 300 and checked by


Name of the Company
 The Company where the summer practice was performed is the Turkish Petroleum Corporation (TPAO).

Location of the Company
 TPAO’s headquarters is in Ankara and it has three districts in Adiyaman, Batman and Thrace regions.

Structure and Scheme of the industrial organization of the company
 Unlike many national oil companies, however, TPAO does not have a monopoly on any segment of the oil business and applies to General Directorate of  Petroleum Affairs for permits on the same basis as other private Turkish and foreign companies. Because of its experience and History in Turkey, TPAO gets to have most of the favorable license areas and has done extensive seismic and exploration work in some of these fields. The company dominates, by its size and scope, most of the Turkish petroleum sector. The government maintains close contact with TPAO through the Board of Directors and through direct contact with TPAO’s top management. In return, TPAO helps the government in developing its energy policy and provides the required technical assistance for the implementation of that policy.

Number of engineers employed and the function they perform
 The number of operating rigs, having various depth capacities between 2000 and 6200 meters, has gradually increased from 5 to 34 in 43 years. Contemporary technology and experience has been applied for all phases of drilling operations. The drilling operations are carried out by 673 technical and administrative personnel. The total number of wellsite, senior and staff drilling engineers who are employed in the field and in the headquarters are 62.

Main sphere of activity of the company
 TPAO has had pioneering efforts on all the branches of petroleum industry and realized investments within the frame of rights granted by law. As an integrated oil company it is engaged in all the activity fields of oil industry from exploration to production, from production to refinery, from refinery to marketing and transportation, by making investments in compliance with the needs of the country.

Brief history of the company
TPAO was founded in 1954. It became a state economic enterprise after the reorganization of the public oil sector during 1983 and 1984. In  1990 TPAO was included among the 50 greatest private and public companies in the world, contributing to the global economic activity as it increased its capital to 3 trillionTL. In 1988 TPAO founded the Turkish Petroleum International Company LTD (TPIC) to take part in every kind of petroleum activity abroad.
 During years 1954-1996 TPAO has carried out 2175.77 crew/month geological and 3013.20 crew/month geophysical studies. Totally 59 oil and 11 natural gas discoveries have been done. 3938328 meters of drilling has realized by 2190 wells. TPAO has produced 51.8 million tons of crude oil and 2.7 million cubic meters of natural gas.
 TPAO has been carrying out its petroleum activities in Turkey and abroad (Kazakhistan, Turkmenistan, Azerbijan, Egypt, Libya, Tunisia and Algeria) for the purpose of satisfying the petroleum requirements of Turkey, continuously, sufficiently and economically.

INTRODUCTION  The purpose of the summer training PETE 300, is that the students of the second year familiarize themselves with the various types of functions performed during the drilling operations. This training provides them with the opportunity to observe the applications of what they will study during their third year. The more interest the students take in the summer practice, the more they acquaint themselves with the practical and applied aspects of the theoretical engineering knowledge they will receive.
 This report of the summer training is about the drilling operations observed at the field and TPAO’s Research Center, which are detailed in the next section.

DESCRIPTION OF SUMMER TRAINING  During the training course, most of the drilling work was observed at the Lilan-1 oil field (Near Adiyaman). Few days were also spent to observe casing and rig assembly at the Karakush-22 and Tokaris oil fields respectively (Also near Adiyaman). And lastly the drilling simulator was observed at the TPAO research center.

Drilling Rigs and Rig Assembly
 Most of the drilling done now a days is by rotary drilling rigs. Rotary drilling rigs can be classified broadly as land rigs or marine rigs. The main design features of land rigs are portability and maximum operating depth. The portable mast, which is suitable for moderate depth wells, usually is mounted on wheeled trucks or trailers that incorporate the hoisting machinery, engines and derrick as a single unit. The telescoped portable mast is raised to the vertical position and then extended to full height by hydraulic pistons on the unit.
 Although drilling rigs differ greatly in outward appearance and method of deployment, all rotary rigs have the same basic drilling equipment. The main component parts of a rotary rig are the :
1. Power system
2. Hoisting system
3. Fluid circulating system
4. Rotary system
5. Well control system
6. Well monitory system
 Most rig power is consumed by the hoisting and fluid circulating systems . Total power requirements for most rigs are from 1000 hp to 3000 hp. Modern rigs are powered by internal-combustion diesel engines.
 The hoisting system provides means to lower or raise drillstrings, casing strings and other subsurface equipment into or out of the hole. The components of the hoisting system are :
1). The Derrick: The mast, or derrick, provides a rigid framework for raising and lowering drill pipe and casing. Also, when the drill pipe is removed from the borehole, it is stacked inside the derrick.
2).  The Crown and traveling blocks: The crown and traveling blocks form a system of    pulleys to raise and lower the tremendous weight of the drill pipe. The crown block is mounted at the top of the mast. It is an assembly of grooved wheels or sheaves over which cable is run from the drawworks and to the traveling block. The traveling block is a matching compound pulley suspended in the derrick by the cables from the crown block. It is made to travel up and down with the downhole loads suspended from it. The two blocks may contain from two to six sheaves each, and they are rated by their load-carrying capacity. The hook is attached, often permanently, to the bottom of the traveling block. It carries equipment (called elevators) for grasping and holding pipe while being raised or lowered into the wellbore. The hook also suspends the swivel and drill string while drilling. It, too, is rated by its load-carrying capacity.
3).  The Draw works: The drawworks is the heart of the rig and generally the largest, most expensive component. Its lifting capacity usually determines the depth rating of the rig. In its simplest form it is a winch with a drum which reels in or feeds off cable over the crown and traveling blocks when raising and lowering pipe. It has brakes for slowing, stopping, and holding the loads. The drawworks also contains a transmission which allows for high-speed hoisting of heavy loads. There is a variable-speed drive for transmitting power to the rotary table. Catheads are mounted on the drawworks to provide torque for screwing and unscrewing the drill pipe and casing. Catheads are also used for picking up single joints of pipe and other equipment too heavy to move by hand. (A cathead is a device for transmitting power through a revolving drum and a rope or cable wrapped around it. In simple form it was familiar to generations of farmers who were accustomed to jack up one rear wheel of a car or truck, remove the wheel, put the vehicle in gear, and use the turning brake drum called cathead.) The drawworks may contain a secondary winch (called a sand reel) used for handling instruments or testing equipment in the borehole.
4).  Swivel: The swivel allows the drill string to turn without twisting the pulley system and its cables. it also supports the entire weight of the rotating string and an entrance to the hollow drill pipe for the injection of drilling fluids. It is set aside while pipe is being tripped in and out of the wellbore. (A complete trip is made when the drill string is hoisted out of and returned to the wellbore for the purpose of changing drill bits, adding drill pipe or drill collars, taking a core sample, etc.) A swivel is rated by its load and pressure-carrying capacity.
As the function of the derrick is to provide the vertical height required to raise sections of the pipe, from or lower them into the hole. The crown block, traveling block and drilling line permit the easier handling of large loads. The drum of the draw works transmits the torque required for hoisting or braking.
 The fluid circulating system removes the cutting from the hole as drilling progresses . The drilling mud travels from the steel tanks to the mud pumps, from the pumps through to the drill string to the bit, from the bit to the surface and back to the suction tank.
 The rotary system includes equipment to rotate the bit. The main components of the rotary system are the swivel, Kelly, rotary table, drill pipes and drill collars.
 The well control system permits, detecting the flow of formation fluids into the well in the presence of drilling fluid which is called a kick, closing the well at the surface, circulating the well under pressure to remove the formation fluids and increase the mud density, moving the drill string under pressure, and diverting flow away from the rig personnel and equipment. Failure of the well control system results in an un-controlled flow of formation fluids and is called a blow out .
 The Well- monitoring system helps the driller to know the depth, penetration rate, hook load, rotary speed, rotary torque, pump rate, pump pressure, mud density, mud temperature, mud salinity, gas content of the mud, hazardous gas content of air, pit level, and mud flow rate.
 The rig assembly was observed on the drilling site of Tokaris where the portable mast was transported by trucks to the drilling site. First it was raised to a suitable height, when the monkey board was attached to it . Then it was raised to full vertical height  by the hydraulic pistons on the rig. The rig was American type drilling rig recommended to drill oil and gas wells up to 2300 m with 9 1/2 inch drill pipes. The 3750 mm height of the mast working floor allowed to install any BOP stack required by this class of rigs .

Drilling Operations
 Drilling operations were observed at the Lilan 1 drilling site. It was an exploration rig. The F-200 type Romanian drilling rigs were being used for the operations. Driven by two diesel engines through hydraulic torque converters wells up to 4000 m in depth can be attained by these rigs. The 5000 mm height of the derrick floor allows to install any BOP stack required by this class of rigs.
 Mainly directional drilling was observed at this site . Slide mud Motor was used for the directional drilling purpose. Without a bent sub or bent housing the motor can be used for normal directional and straight hole drilling. From time to time rotary drilling was also done. After the completion of the desired angle and depth of directional drilling was done, the drilling was completely shifted to rotary type drilling. But because of the irregular trajectory change by the mud motor to attain the desired 40 degree inclination, the drill string was stuck in the irregular geometry hole. After trying different methods to free the string failed. The drill string was withdrawn and the inclined path redrilled to make a smoother hole .
 The Lilan-1 oil well is located next to Attaturk dam lake. The oil reservoir was estimated to be under the well, therefore directional drilling was applied in this well. Although drilling was done by TPAO engineer, directional surveying was performed mainly by experts from Baker Hughes-Inteq.
 At the beginning of observation, the well had been drilled to the measured depth 1627 m the True vertical depth being 1612.84, inclination was 30.9 degrees, the azimuth was 228 degrees and the lithology was Germav. When the T1000 pump became out of work the circulation of drilling fluids was continued by 2 PN 700 pump. At the last day of observation the MD was 1846 while TVD was 1783.2.After this depth the string was tripped out for changing the bit. The last inclination before tripping operation was 41.6 degrees. The lithology was still Germav.

Dull Bit Grading System
 Another system that was observed was the dull bit grading system. Careful inspection of the dull cutting structure and bearings can give us a good handle on the bits dull characteristics which can affect our next bit selection, break in procedures and operating practices. Grading a dull bit and evaluating those findings is a simple operation that can increase our drilling efficiency while lowering drilling costs.
 For example at Lilan 1 bit No.10 that was SS44GF or the SECURITY DIV. company bit 137.Bit 137 was milled tooth, for soft formations with low compressibility strength, high drillability, and sealed friction bearing gage protected. This bit was changed giving the reason as 33 WT A E I NO PR . 33 described the cone number and the measure of lost, worn and/or broken cutting structure, WT representing worn teeth/cutters. A as all rows E describes seals effective. I for in gage. NO for no other dull characteristics. PR for the reason to pull the bit out that was the penetration rate. It was replaced by M15SOD or Smith Tool Company’s 445 (Insert tooth for soft formations with sealed roller bearings gage protected).

Basic drilling fluid Procedures and testing
Baroid Mud Balance
1). Remove lid and fill cup to the top with sample to be tested. If air bubbles have been trapped in the mud, tap cup briskly until they break out.(In testing cement, puddle the slurry 25 times.)
2). Replace lid and rotate  until firmly seated, making sure some mud squeezes out the vent hole.
3). Wipe mud from exterior of balance.
4). Place balance on base with knife edges on fulcrum rest.
5). Move rider until instrument is in balance, as determined by spirit level.
6). Read mud weight and hydrostatic pressure or gradient at edge of rider nearest fulcrum.
Marsh funnel viscometer
1). Hold funnel in upright position with index finger over outlet.
2). Pour the test sample freshly taken from the mud system, through the screen in top of funnel until mud level just reaches the under side of the screen.
3). Immediately remove finger from outlet tube and measure number of seconds for a quart of the sample to run out.
Baroid Rheometer
1). Place a recently agiated sample in a suitable container and lower the instrument head until the rotor sleeve is immersed exactly to the inscribed line. To hold in this position, tighten the lock screw on the left leg of the instrument. With the gear shift at high speed setting, rotate the crank for about 15 seconds, release to 600 RPM setting and continue cranking.
2). Wait for the dial reading to come to a steady value. This is the high speed reading (600 RPM). Move the gear shift lever all the way up, crank and wait for the dial reading to come to a steady value. This is the low speed reading (300 RPM).
Baroid Standard Filter Press
1). Assemble the following dry parts in this order: base cap, rubber gasket, screen, a sheet of filter paper, rubber gasket, and cell. Secure the cell to the base cap.
2). Fill the cell with the sample to be tested within 1/4 ’’ of the top. Set the unit in place in the filter press frame.
3). With the regulator T-screw in its maximum outward position, open the valve to the cell. Apply 100 psi pressure to the filter cell by rapidly screwing the regulator T-screw into the regulator. Timing of the test should begin now.
4). At the end of 30 minutes, close the valve to the cell rapidly and open the safety-bleeder valve. This releases the pressure on the entire system. Return the regulator T-screw to its maximum outward position.
5). Read the volume of filtrate collected in the graduated cylinder.
pHydrion Dispenser
1). Remove about a one-inch strip of indicator paper from the pHydrion Dispenser which is judged to be within the range required, and place it gently on the surface of the mud.
2). Allow sufficient time to elapse for the paper strip to soak up filtrate and change color.
3). Match the color of the strip with the chart on the side of the dispenser from which the strip was taken and read the pH of the mud.
4). If the color is off the scale and cannot be matched, repeat the test with a different indicator strip judged to be closer to the pH range required.
Sand content
1). Pour mud into the baroid content tube until it fills up to the mark labeled ‘Mud to Here’. Then add water to the mark labeled ‘Water to Here’. Cover mouth of the tube with thumb and shake vigorously.
2). Pour this mixture through the screen, being careful to wash everything out of the tube with clear water through the same screen. Wash sand retained on screen with a stream of water to remove all mud and shale particles.
3). Fit funnel down over top of screen, invert slowly, turning tip of funnel into mouth of tube, and wash sand back into tube with a fine spray of clear water on the back side of the screen. Allow the sand to settle.
4). Observe the quantity of sand settled in the calibrated tube as the sand content of the mud.
Field observation
 Basic drilling fluid testing procedure was also observed on the drilling rig. The basic procedure that was followed :
1). To weigh the mud with the help of a mud balance.
2). The Marsh funnel was used to measure the time required for a mud sample to flow through it which was found to be 105 seconds in our case.
3). API filter having an area of 45 sq.-cm was used operating at a pressure of 100 psig. The filtrate volume collected was 5 units of 1000 units in a 7.5 minute time period.
4). The pH of 10.5 was found which expresses the concentration of hydrogen ions in a mud system.
5). The rotational viscometer was used with 600 rpm finding viscosity 92 and 300 rpm finding viscosity 64. The plastic viscosity was PV = (600 dial reading - 300 dial reading) i.e. 92-64 = 28. The yield point was found by YP = (300 dial reading - PV) i.e. 64-28 = 36.
6). The sand content is measured by using a 200 mesh screen and a glass tube. The percentage of sand by volume in mud is determined.

Casing and cementing
 The job of running a long string of casing into the hole, landing it at the desired casing point, and successfully cementing it requires careful planning. Failure to get the pipe on bottom usually results in additional expense and may result in loss of hole. All operators condition the hole by circulating before running the casing. Some operators circulate mud through the hole once, others circulate until the returns are satisfactory. In most cases, no major change in the chemical treatment of the mud is made during the circulation period. Usually an effort is made to adjust the mud properties to the conditions that existed during the up-hole drilling, which requires normal, chemical, viscosity-reducing treatment.
 The amount of cement to be used in casing-cementing depends on the total volume of slurry required and on the volume of slurry per sack of cement. The total volume of slurry required is dictated by the casing dimensions and the dimensions and the volume of the hole. The hole volume is determined by the bit size and the hole enlargement. The extent of hole enlargement depends on local field conditions, the type of drilling fluid, and the cement additives used.
 The casing operation was observed at Karakush-22 which was a production well and the same F-200 type Romanian rigs were in operation. The 7 inch N80 casing was run to a total depth of 2669 m with float shoe being at the bottom, which includes a back pressure value and a discharge. Above the float shoe was the float collar. The function of the float collar is to serve as a floating equipment. Above the float collar the by pass baffle and by pass plug was set. The by pass plug acts as a wiper plug and sits on top of the by pass baffle. At 2000 m the DV (A special cementing collar) was run. After the first cement circulation the opening bomb was run followed by the closing plug. Low quantity of 32 API oil was found from this well.

Drilling Simulator
 Drilling operations was also observed at the TPAO research center by using a drilling simulator mainly used to train drilling employees. The rig components and some drilling functions were viewed, most of which have been discussed above.
 A brief explanation of kick was also given. The flow of formation fluids into the well is called a kick. Formation fluids that have flowed into the wellbore generally must be removed by circulating the well through an adjustable choke at the surface. The bottom hole pressure of the well at all times must remain above the pore pressure of the formation to prevent additional influx of formation fluid. However, a complicating factor is the danger of fracturing a weaker stratum that also is exposed to the hydraulic pressure. Fracturing of an exposed stratum often results in an underground blowout in which an uncontrolled flow of formation fluids from the high-pressure stratum to the fractured stratum occurs. Thus, the proper well control strategy is to adjust a surface choke so that the bottom hole pressure of the well is maintained just slightly above the formation pressure. CONCLUSION Turkey is a developing country and the energy demand of the country is increasing day by day. Oil has the biggest share (46 %) in total primary energy consumption, while natural gas has a share of 10 %. Due to the diversification efforts of  government in energy sources, use of natural gas that was introduced  into Turkish economy has been growing rapidly. Natural gas consumption (6.8 billion cubic meter) is assumed to increase by 11% and will reach to 31 billion cubic meter with a share of 18 % in total consumption in 2010. So there is a great need to find new oil and gas reserves and drill more wells to increase the country’s oil and gas production. And there is also great need to upgrade the technology. As the latest drilling rigs in operation in Turkey are the Romanian type rigs which were bought in 1979. And lack of technological expertise in some areas, foreign companies are hired and have to be paid huge amounts of foreign exchange. Another area of concern is the lack of theoretical knowledge in the workers.
 Although of some concern the above mentioned problems can be neglected if compared with other benefits an engineering student gets by working on a Turkish oil field. The engineers graduated from excellent universities including foreign graduates are highly able and give proper knowledge and guidance. The workers also help by explaining their experiences. And the presence of foreign experts gives the student an international broad view. The modern drilling simulator at the Turkish petroleum research center is excellent in giving predrillsite experience to both a student and other drilling employees. In short the summer practice is an excellent opportunity for a student to acquaint with the practical and applied aspects of drilling engineering.

REFERENCES 1). Bourgoyne Jr., A.T., Millheim, K.K., Chenevert, M.E., Young Jr., F.S., (1986), Applied drilling engineering, Society of petroleum engineers, Richardson.
2). TPAO Introduction Guide, 1997.
3). R.A.Bobo, R.S. Hoch, G.S.Boudreax, R.R.Angel, Keys to successful competitive drilling, (Houston:Gulf Publishing Company, Book division, 1958), p.67.
4). Canadian Association of Oilwell Drilling Contractors, Introduction to Oilwell Drilling and Servicing ,Gulf Publishing company, Book division,1982.
5). B.C.Craft, W.R.Holden, E.D.Graves, Jr., Well Design Drilling and Production, Prentice-Hall, Inc., 1962.

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