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
M. Evren OZBAYOGLU.
DESCRIPTION OF THE COMPANY
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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