ME4105 NUS Offshore Oil and Gas Technology Lecture 2

8/11/2019 ME4105 NUS Offshore Oil and Gas Technology Lecture 2

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Offshore Oil & Gas Technology


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DRILLING TECHNOLOGY


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Early Drill ing - Percussion The process of drilling wells dated back to several

thousand year in an effort to find water and salt. The Chinese were the first to reach a level of drilling

sophistication, with the first spring pole drilling technique.

By 600 B.C. the Chinese were using percussion tools,the forerunner of cable tools to dig brine wells.

The Chinese developed a method of pounding holes intothe earth using bamboo tubes and bronze bits. Theycould drill about two a day by alternatively lifting anddropping the metal drilling tool (sometimes weighing 300

pounds) in the hole. Water was used to soften the rock formation in the hole,

making it easier both to drill and to remove the cuttings.

Several hundred of feet in depth could be reached, butcould take as long as years to complete a single well.


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Spring pole drilling a Jobard drilling machine used in Brussels in 1828


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Percussion Bit the constant raising and dropping of the bit drills the hole


7/51Col Drake and the first commercial well drilled


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Wooden derricks and cable-tool drills


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Percussion Drilling Percussion drilling, or cable-tool drilling, is accomplished

by repeating raising and dropping a heavy metal bit into

the earths surface, eventually punching a hole

downwards.

One of the earliest methods of drilling and that Edwin

Drake used in 1859 was cable-tool drilling.

Cable-tool drilling can be effective, especially in hard-

rock formations.

But cable-tool drilling has following main disadvantages:

Drilling must be stopped frequently and the bit pulled from the

hole so that pieces of rock, or cutting, chipped away by the bitcan be removed by a bailer.

Cable-tool drilling cannot drill soft-rock formation. Splinter rock

formation tend to close back around the bit and wedge it in the

hole

Formation caving or collapse could happen in soft formations.


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Standard cable tool rig


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Cable Tool Rig The derrickis the tower that supports the components.

At the top of derrick(or mast) is the crown blockover

which the drilling line run. Power comes from an engine which is transmitted by

belt to the band wheel. This is connected by the pitmanarmto one of the walking beamwhich raises and

lowers the drill bit. The bullwheelis the largest pulley on the rig used tospool the hemp drilling rope, which has to be longenough to reach the bottom of the hole. It is also used topull the tool stringfrom the hole.

To increase the lifting ability, another spool called thecalf wheelis added, along with a multiple sheave crownblock and a multiple sheave traveling block.

The bailer is attached to the sand lineand is used toremove cutting and fluids from the wellbore.


12/51Standard cable tool rig


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Cable-Tool Drilling From the latter half of 1800s and early 1900s, cable-tool

drilling rigs drilled a large number of wells.

Wells were often drilled to 3000 to 4000 feet depths. Stationary cable-tool drilling rigs with their pyramid-shaped

wooden derricks were a common sight in the oil patchfrom the 1860s to 1920s.

Then, the portable cable-tool rig, which are smaller andcontained many steel components, became standard.

1950s all but disappeared from the scene largelyreplaced by rotary drilling.

The early so-called standard rigs had very poor safety standard. Therewas no clutches or transmissions between the engine and the rig. Theonly way to interrupt the power was to stick a board between thedrilling rope and the bullwheel, or by pulling a cotter pin that thepitman arm to be slipped off the moving band wheel crank. That as a

result had caused accidents. Despite their drawbacks, cable tool rigswere used all over the world as the demand for oil grew.


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Rotary Drilling The concept of rotary drilling is not new. The Egyptians,

were boring into the ground using a rotary motion in3000 B.C.

The first rotary drilling rig was developed in France in

1860s. In 1860, patents were issue to Leschot, a French

engineer for the use of diamond bit for drilling holes in

hard rock for a tunnel construction project in the Swiss

Alps. The rotary drilling system was complete with a

circulating system of drilling fluid to dissipate the heat

generated by the scraping of the diamonds on hard

rocks.

But rotary drilling did not catch on at first because it

was erroneously believed that most petroleum was

associated with hard-rock formation, which could be very

effectively drilled with cable tools.


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Rotary Drilling In 1880s, the Baker brothers, successfully drilled water

wells in soft formation of the Great Plains of USA, an

area where cable-tool rigs were not having muchsuccess. The Bakers rig has a fluid-circulating system to

bring the cuttings to the surface. The Corsicana oilfield

was discovered while drillers were search for water.

Around 1900s, several unsuccessful attempts were madewith cable-tool to drill the great Lucas wells in Spindletop

due to formation caving.

In 1901, the great Lucas well at Spindletop was drilled

successfully using the Hamill brother using a rotarydrilling rig brought from the Corsicana.

The previous experience of these men with the rotary

drilling process and their understanding of using mud

circulation for drilling soft formation subject to caving or

collapse were the key to success.


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The Lucas Gusher at Spindletop. Jan 10, 1901


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Rotary Drill ing With the success of the rotary drilling at Spindletop,

many oilmen began to switch from cable-tool to rotarydrilling.

In rotary drilling, the drilling action comes from pressingthe teeth of a drill bit firmly against the ground andturning, or rotating it.

At the same time as the drill bit was rotated, a fluid,called the drill mud is forced out of special openings, ornozzles in the bit. The mud jets out of the bit nozzleswith great velocity, displaces and move the cutting madeby the bit teeth away from the teeth, and in the process

continuously expose fresh, uncut rock to the teeth. The mug also lifts the cuttings off the bottom to surface

for disposal

This way, drilling does not have to stop in order to

remove cuttings.


18/51Rotary drill rig


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Rotary drill rig


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Rotary Drilling Rig


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Rotary Drill ing Rig

A rotary rig have five major system

essential to the operation:

The drill string and bit

The fluid circulation system

The hoisting system

The power plant

The blowout prevention system


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Rotary Drilling Rig

(OR DERRICK)


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Personnel involved in a drill ing operation


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Drill ing Personnel Drilling Superintendent Overall manager of field drilling operation.

Supervises the activities of several drilling rigs and personnel working

in a given area. Toolpusher second in command. Direct field supervision of drilling

operation, generally responsible for one or more rigs to make sure

that proper materials and personnel are available to accomplish

necessary jobs.

Driller the employee in charge of the rig and crew for a given tour(or shift of duty) and who primarily operates the drilling equipment.

Roughneck sometimes called the rotary helper, this worker is part of

the crew who assist the driller in floor work, i.e. jobs on the rig floor,

including making connections, pulling pipe, and rig maintenance and

cleanup. Derrickman the crew member whose work station is the pipe rack in

the uppermost part of the derrick (also known as the monkeyboard)

when the drill pipe is being raised from or lowered into the hole.

Mud engineer the person responsible for maintaining the proper

chemical composition of the drilling mud.


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Drill String and Bit The drill string and bit - the most crucial part of the

rotary drilling system that physically creates the hole. As the term rotary drilling applies, the rotation of the

drill string and drill bit rotates thereby applying a cuttingaction against the rock at the bottom o the hole.

The rotating action is achieved through the operation ofthe drill string and bit system.

The swivelis latched onto the hook at the bottom of thetraveling block, and serves the dual function ofsupporting the weight of the drill string and allowing the

string to rotate. Attached to the swivel is a four or six sided piece of pipe

called the kelly. The shape of the kelly allows it totransfer the rotating motion of the rotary tableto the drillstring.


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Drill string and bit


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The kelly is mounted in a similarly-shaped opening in a

device called the Kelly bushing. The kelly bushing isheld in the rotary table on the rig floor and supplies the

necessary torque from the rigs power system to turn the

drill string. The kelly is free to move up and down

through the rotary table, while it is being turned. In thismanner, the drill string is allowed to steadily move down

the hole as it rotates and drill deeper.

Attached to the kelly is the drill string, comprising the

ordinary drill pipeand the heavier drill collars. Drill

pipes are comes in 30 ft section, calledjoints, and is

threaded on each end to allow the sections to be joined

together. Below the drill pipes and immediately above

the drill bit are the drill collars.

Drill String and Bit


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Drill collars differ from ordinary drill pipe in that they are

thick-walled and much heavier. Drill collars are used to add weight on top of the drill bit,

which improve the cutting action. They are also used in

certain instances to help keep the hole straight.

The drill bit, one of the most important parts of the entiredrilling process, is attached at the end of the drill string.

Basically the job of the drill bit is to advance the hole by

breaking up and dislodging the formation so that the

drilling fluid can remove the cuttings.

All drill bits have passages that allows drilling fluids to

pass through them and sweep away the rock cuttings as

the bit drills deeper.

Drill String and Bit


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Drill Bit There many types of bits, each design to fit a particular

need dictated by the type of soil and rock encountered. When shallow wells are drilled through soft soils and

formations, one bit may be used for the entire job.

When drilling deep wells through many different types of

rocks and soil, bits may have to changed many times,either as they wear out or as soil condition change.

There are literally dozens of varieties or bits each

designed for a specific applications.

Factors affecting bit selection type of formation to beencountered, use of mud motor, turbine, percussion, or

directional drilling; the anticipation of abnormal

temperatures; and whether or note core are desired.


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Bits are classified by the International Association of

Drilling Contractors. The IADC lists six categories of

formation that affects bit selection.

Steel Tooth Rotary Bits There are at least nine

sub-types of these, each differing in shape bearings,

used, etc.

Insert Bits which have tungsten carbide inserts

implanted in them.

Polycrystalline Diamond Compact Bits (PDC)

have inserts of that material attached to the tungstencarbide inserts mentioned above.

Diamond Bits bits implanted with industrial

diamonds for use in extremely hard formations.

Drill Bit


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Roller Cone Drill Bit Roller cone bit (also called a rock bit or tricone bit) is the

most common type of bit used worldwide. The cutting action is provided by cones which have

either steel teeth or tungsten carbide inserts.

These cones rotate on the bottom of the hole and drillthe hole predominantly with a grinding and chipping

action. Roller cone bits are classified as milled tooth bitor

insert bitsdepending on the cutting surface on thecones.

The cones of the three cone bit are mounted on bearingpins, or arm journals, which extend from the bit body.The journals allow each cone to turn about it own axis asthe bit is rotated.

The use of three cones allows as even distribution of the

weight and a balance cutting structure.


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The major advantages of roller cone drill bit(rock bit) design:

Improved cleaning action using jet nozzles

Using tungsten carbide for hardfacing of the teeth and

gauge protection Introduction of sealed bearing between the cone and

journals to prevent the mud causing premature failure

due to abrasion and corrosion of the bearings.

Roller Cone Drill Bit


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Milled teeth roller bit


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Cross sectional view of mill tooth bit


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Sealed milled tooth bit


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Milled tooth bit nomenclature


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Tungsten carbide insert bit


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Tungsten carbide insert bit


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Tungsten carbide insert bit nomenclature


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Action of roller cutter

on rock surface


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PDC Bit In the 1980s, a new type of drill bit known as Polycrystalline

Diamond Compact (PDC) was introduced. Small discs of man-

made polycrystalline diamond are bonded to a cementedtungsten carbide substrate to produce an integral blank.

The hardness and wear resistance of diamond make the PDCbit an obvious material to be used for a drilling bit.

The small discs used for PDC bits may be manufactured inany size and shape and are not sensitive to failure alongcleavage planes as with natural diamond.

Effective fluid circulation across the face of the bit is veryimportant to prevent overheating of the diamonds and matrix

material and to prevent the face of bit becoming smeared withthe rock cutting (bit balling).

PDC bits have been run very successfully in many areasaround the world, especially when run in combination ofturbodrills and oil-based mud.


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Shallow cone PDC bit


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PDC Drill Bit

The major disadvantage of PDC bits is their cost. However, they are cost effective when drilling formations

where long rotating hours (200 to 300 hours per bit) are

required.

PDC bits have not moving parts, hence, they tend to lastlonger than roller bits. This results in a reduction in the

number of round trips and offsets the capital cost of the

bit. This is especially important in areas where operating

costs are high (e.g. offshore drilling).

Diamond Bits


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Diamond Bits Diamond bits are normally used for hard and abrasive

rock drilling and when longer runs are required in order

to reduce trip time, i.e. in deep wells and in offshoredrilling, where the rig costs are very high.

The cutting elements of a diamond bit consists of a largenumber of small-sized diamonds geometrically

distributed across a tungsten carbide body. The bit does not employ moving parts.

Diamond is the hardest mineral known to man and has avalve of 10 on the Mohs scale of mineral hardness.

The thermal conductivity of diamond is also the highestof any material, which allows the diamond to dissipateheat from its cutting structures very quickly.


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Diamond bit


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Diamond bit


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Diamond bit


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The size of diamonds used will determine the type of

rock to drilled.

Large diamonds are used to drill sock rocks, since these

rocks are easily penetrated

Small-size diamonds are used for hard rocks, since the

diamonds cannot penetrate very far in such rock.

The majority of diamond bits are currently manufactured

as coring bits. A diamond coring bit contains a central

hole corresponding to the size of core required. A typical

coring assembly consists of a diamond coring bit, a core

barrel, drill collar and drill pipe to surface.

Diamond Bits


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ME4105 NUS Offshore Oil and Gas Technology Lecture 2