Davorin Matanović

Drilling

MUD PUMPS AND CONDITIONING EQUIPMENT

MUD PUMPS AND CONDITION

ING EQUIPMENT

• The main components of fluid circulating equipment

for rotary drilling are:– mud pumps,

– rotary hose and stand pipe,

– swivel,

– drill stem and bit,

– mud return line and

– mud tanks.

• Mud conditioning equipment includes:– shale shakers,

– desanders and desilters,

– decanting centrifuges,

– mud-gas separators and vacuum degassers,

– mixers and agitators,

– mud pit instruments, and

– storage and handling equipment for mud components and mud additives.

Mud pump• The mud pump is the primary component of

any fluid circulating system.

• It provides the driving force that sends the fluid through the route that it must travel.

• Pump are powered by diesel engines, gas engines or electric motors.

• Those designed for drilling have ratings up to1600 kW.

• They are capable of moving large volumes of fluids (up to 3500 dm3 �min-1) at pressures as high as 390⋅105 Pa.

• They are usually duplex, double-acting, reciprocating types or triplex, single-acting.

Centrifugal pumps

• Centrifugal pumps, used in the circulating system on the rig are used when pressures are up to 40⋅105 Pa.

• General service includes:– supercharging the mud pumps,

– supplying water for wash down,

– cooling brakes,

– mixing mud, and

– circulating mud through the various conditioning devices.

Mud pits (tanks)• They are essential part of the circulating system.

• Their main function is to accumulate mud circulated from the hole and provide a constant supply to the suction of the pump.

• Their secondary function is to serve as a reservoir in which the mud stream is cooled and allowed to slow down so that the cuttings can settle out.

• Also various materials and chemicals can be added for treating and conditioning mud.

• Mechanical mud conditioning devices are usually mounted on steel mud tanks.

• A small tank for mixing chemicals with water and feeding them into the mud stream is used where the mud must be chemically treated.

• Likewise, a mud hopper for mixing dry materials with the drilling fluid is a requirement when weighted mud is being used.

• Storage facilities are required for protecting dry mud materials and chemicals from the weather (containers, silo etc.).

• A shale shaker removes nearly all of the large particles from the fluid stream.

• Mud agitators are needed to maintain weighting material in suspension.

• A degasser removes entrained gas from the mud much more quickly than allowing the mud to stand still in pit.

• Desanders, desilters and mud centrifuges are useful to separate sand and fine solids from liquid mud, to salvage weight material, and to condition the mud for minimum additions of water and chemicals.

Mud pump construction

• Mud pumps for drilling purpose are of reciprocating piston type.– Piston pumps with 2 or 3 cylinders are often in use.

– When mud is sucked and pumped with only one side of the piston it is called single-acting, when it works with both sides of the piston, it is called double-acting pump.

• Reciprocating pumps have cylinders, containing pistons that move back and forth inside a liner. – One end of the pump, power end, is driving the

working parts.

– The other end of the pump, the fluid end, is concerned with intake and output of the fluid being pumped.

• Each cylinder is attached to intake valve and discharge valve located at the end of the stroke area of piston.

• A belt-driven pulley or a chain-driven sprocket from the power source is attached to the pinion shaft and causes it to turn a small gear-a pinion.

• The pinion drives a larger gear –the bull gear.

• It is attached to the crankshaft; the crankshaft turns to give a back-and-forth motion to the connecting rods.

• Connecting rods are linked to the crossheads, which are connected to the piston rods with the piston on the end.

• Some pumps feature a chain and sprocket reduction drive instead of gears.

Single-acting, triplex piston pump

Hydraulic part – Fluid end

• Fluid end of a duplex pump has two cylinders. – Inside each of these cylinders

a piston moves back and forth.

– On either end of each piston’s travel, the cylinder has one intake and one discharge valve, making four valves for each cylinder.

– The movement of the piston causes the valves to act in pairs; both an intake of mud into the pump and a discharge of mud from the pump cylinder occur during each back-and-forth movement of the piston.

• Piston rod works inside the pump through a stuffing box and gland. – The gland prevents fluid from

leaking around the rod.

– A piston is attached to the rod, and fluid pressures on the two faces of the piston alternate from suction to discharge.

– The pressure seal between piston and liner must be effective, although the piston must still be able to slip freely inside the liner.

– The liner packing makes a pressure seal between the two ends outside the liner.

• Valve seats must be absolutely pressure-tight to prevent leakage.

• The pump valves must be free to move vertically the required distance, and the resilient inserts must form a positive seal on the seats.

– Pump output capacity is changing according to the well construction.

– Different pumps may have different pressure ratings for the same liner diameter, depending on their mechanical design and input horsepower rating.

– Pressure ratings are determined by the load on the piston rod, which is the product of the pressure multiplied by the area of the piston exposed to fluid pressure.

– With large liner diameters, low-pressure and high-volume output are obtained.

– Small liners permit high-pressure, low-volume fluid delivery.

• Most rig pumps run at essentially constant speed for a given engine throttle setting.

•When the load of the engine or the discharge pressure from the pump for a given liner size becomes too great, a smaller liner must be used: output volume is less for a smaller liner than for larger sizes at the same speed.

• Theoretical pump delivery for all kinds of reciprocating piston pumps is:

Where:

Q – theoretical pump delivery, m3�s-1

Ac– piston area (or inside liner cross section area), m2

s – piston stroke length, m

i – number of cylinders

nk

– number of piston strokes, s-1

Ak

– piston rod cross section area, m2

z=1 for single-acting pump

z=2 for double-acting pump

( )[ ]1−⋅−⋅⋅⋅⋅= zAzAnsiQ kck

• Real pump delivery (Qs) is smaller than

theoretical due the inertia of mud columnin the intake line, slow valve opening and closure and wearing out of piston seals, and can be calculated as:

Where:

ηv

– volumetric pump efficiency (0,88 to 0,90) for double acting pumps, while for single-acting pumps with thesupercharging centrifugal pump it equals 1,0.

Q Qs v= ⋅η

• Overall pump efficiency is fromη=0,77 to 0,88:

� ηh

is hydraulic pump efficiency; ηh=p/p

h,

• Where:

p – pressure at the pump output, Pa

ph– pressure at the piston, Pa

• ηh=0,95 to 0,97.

η η η η= ⋅ ⋅v h m

� ηm

mechanical pump efficiency; ηm=N

i/N,

� Where:

N – power at the pinion gear axis, W

Ni– power that pistons transfer to the mud N;

� ηm=0,90 to 0,95.

Pump delivery

a) single-acting triplex pump,

b) double-acting, duplex pump

• Theoretical power needed to drive the pump is:

• Real power Ns

at the pulley, sprocket, that means on the powered axis of the pump is calculated as:

N Q p= ⋅

ηN

N s =

Pump

delivery

• Hydraulic power that can be achieved is:

Nh= p⋅Q/η

h

Where:

Nh– hydraulic power, W

p - pressure, Pa

Q – pump delivery, m3s-1

ηh

– hydraulic pump efficiency

For assumed hydraulic pump efficiency of 90%, and overall mechanical efficiency of 80%, hydraulic output power is considerably less than installed:

Nh=0,9⋅0,8⋅N

m=0,72⋅N

m

Where:

Nm– installed motor power, W

Piston

movement

inside cylinder

Single-acting mud pump schematic

Double-acting mud pump schematic

( ) ϕϕ 22

sin2

cos1 ⋅⋅

+−⋅=o

rr L

RRx

Where:

x – piston distance from the “dead point”, m

Rr– crankshaft radii, m

Lo– rod length, m

ϕ- angle of crankshaft movement, °

Linear piston velocity equals to the first derivation of the path (x) over the time (t):

⋅

⋅+⋅⋅== ϕϕω 2sin

2sin

o

rr L

RR

dt

dxv

Where:

v – piston velocity, m⋅s-1

ω – angle velocity, s-1

Piston acceleration equals to second derivation of path over the time:

⋅+⋅== ϕϕω 2coscos2

L

RR

dt

dvak

Where:

ak – piston acceleration, m⋅s-2

Efficient operation

• The suction lane from the mud tank to the pump should be of large diameter, short and straight.

• Changes in size and direction of the line should be avoided if possible to keep losses to a minimum.

• Valves should open fully and should be the same size as or larger than the suction opening of the pump.

• A suction pulsation dampener, or desurger, reduces hydraulic hammer.

Supercharging pump

• Centrifugal supercharging pumps increase suction line pressure.

– The increased pressure produces higher pump volumetric output and allows higher-speed operation, and smoother discharge pressure.

– The centrifugal pump should have a fluid capacity that is at least equal to that of the reciprocating pump at maximum speed and largest liner size.

Discharge piping

• Discharge piping should be kept as simple as possible. – Every elbow, tee, bend, valve

not opening fully, or change in pipe size may create points of reflection for water-hammer or hydraulic knock that can cause severe vibrations.

– Long-radius bends are better than right-angle turns.

– All sections of the line should be firmly anchored to a rigid structure, and high-pressure hose ends should be tied securely against the possibility of their whipping free in case of a break.

– Piping should be welded rather than screwed.

Pulsation

dampener

• Pulsation dampener absorbs discharge pressure variations and thus reduces pear pressures and permits smoother volumetric pump output. – This action minimizes

vibrations in the discharge line and the rotary hose and gives a more constant flow rate through bit nozzles.

– It should be installed as near to the pumps as possible.

– Nitrogen charging pressure in dampener must be held to the manufacturer’s recommendations.

1) lower plate2) body3) cover plate4) diaphragm5) diaphragm insert6) stabilizer7) screw8) pad9) charging valve10) valve shield11) pressure gauge12) valve cover13) screw14) stud bolts15) nut16) cover plate seal17) lower plate bolts

Pressure relief valve

• A pressure relief valve should be installed in the discharge line immediately next to the pump. – Its primary purpose is to protect the pump

when the discharge line, another part of the hydraulic system, or bit nozzle becomes plugged.

– A shear-type relief valve at a setting too close to a operating pressure will release pressure too frequently.

– Automatic-reset relief valves that can be adjusted to the pressure relief setting desired are available.

– Any relief valve must be placed in front of the discharge screen, or strainer and must not have a shutoff valve between it and the fluid end, since otherwise it cannot protect the pump.

PISTON• Failed piston will allow fluid to pass from

one side to the other. • Pressure in the bypasses or washed-out

area exerts a force that pushes the piston against the liner wall on the opposite side.

• When the piston is forced against the liner the flange of the piston body wears away and appears to be flat.

• Any flatness or out-of-round condition increases the clearance between the piston flange and the liner bore and shortens the expected life of a piston.

• A piston costs only one-fourth to one-sixth the price of liner.– If a leaking piston is used until it fails,

the liner as well as the piston may have to be replaced.

• The piston must be made up with the proper torque, for too little torque causes the piston to work loose and permits fluid to wash between the rod and the taper.

– Proper torque is very important on the API-HP taper to ensure that the joint is pre-stressed properly.

– The flange of the piston increases in diameter approximately0,0508 to 0,1016 mm as the piston is forced up the taper.

mm)4,6(

4/1 ′′

Liners

• Pistons and liners are so closely related that they must be considered together. – Liner life depends on piston clearance and

operating pressure, the effects of corrosion, and the effects of erosion by sand and silt in the fluid

– Piston and liners life can be increased with the use of corrosion-resistant liners when corrosion problems exist.

– Sand and small abrasive particles in mud cause excessive wear of pistons and liners; desanders and desilters pay for themselves by extending liners life.

– Clearance between the liner and piston body should be less than 0,762 to 1,194 mm for high pressures. • A clearance of 1,016 mm will result in a piston

life no more than half the piston life that can be expected from new parts with a clearance of0,254 mm.

– Whenever a new liner is put into a pump, a new piston should be installed too.

Construction of liners

• Standard steel liners are either induction hardened or carburized.– After hardening, the

bore is usually honed to a smooth surface.

• Chrome iron liners (centrifugally casted) are premium liners that exhibit superior resistance to abrasion and corrosion.– Finally they can be

processed as unique part or can be of bimetal construction (inside high-quality sleeve in steel body; can also be produced from ceramics.

Centrifugal pumps• A centrifugal pump transfers

energy to a liquid through action of a rotating impeller. – The liquid, taken into the suction

line of the pump, is directed against an impeller rotated by a drive shaft.

– The shaft is driven by electric motor or through drive belts from some other prime mover.

– As the impeller spins inside the housing, its guide vanes hurl the liquid outward from the axis of rotation.

– Because the housing is enclosed, the liquid is forced out the discharge line at a pressure much higher than that on entering the pump.

OUTLET

IMPELLER

VANE

INLET

• A single-stage centrifugal pump with semi open impeller is the type usually employed in drilling rig service.

DRIVE

SHAFT

DISCHARGE

OUTLET

STUFFING

BOX

SUCTION

INLET

IMPELLER

HOUSING

IMPELLER

Reserve pit• Reserve pits have little to do

with fluid circulation, except for the special occasion when mud is circulated through them. – They are used chiefly as a

depository for waste fluid, cuttings, and trash that accumulates as a well is drilled.

– Usually there is no provision for fluid transfer from the reserve pit to the active system.

– In fact due to environmental protection purposes, they are abandoned in modern drilling process, and the so called “closed systems” are used.

– Cuttings and waste are collected in barges and hauled away for disposal.

Steel

tanks• The advantage they offer is that

their volume is known, they can be easily cleaned, and they make possible a positive pressure for the suction of the pumps

• They should be large enough to provide an adequate settling area if settling is desired.

• They should also have sufficient capacity to contain the mud volume required in working system when drill pipe is on bottom at total depth and have a reasonable reserve of mud in case of lost circulation or the unloading of mud by gas kick;– recommended reserve volume is

about 20% of the entire well volume.

• According to fluid flow from the well, tanks are arranged as follows:1. shaker tank with sand trap;

2. reserve tank;3. reserve mud pit (tanks); and4. suction tank.

• From the suction tank, mud goes directly to the mud pumps.

• The tanks are usually provided with stirrers and mud guns for agitating the mud.

• Two or more jet siphons are installed to permit removal of surplus mud that may accumulate in the tanks.

• If a degasser is used, the common arrangement is to take suction out of the second compartment of the shaker tank and return the degassed mud to the next tank.

• If desanding and desilting units are used, they are operated downstream from the sand trap and degasser.– Degasser, desander and desilter equipment may be mounted on the shaker tank and reserve tank, with built-in piping for the pumps.

– Solids control equipment should always be placed in an order according to size of particles removed.

• The shaker tank is usually provided with at least two compartments and arranged with one or more vibrating screen shale shakers. – Slugs are pumped into the drill string before trips to empty

the drilling fluid, preventing contamination of crew and rig floor.

– Mud mixing pumps and hopper are housed on a skid.

– Mud and chemicals are stored in the mud house, close to the mixing unit.

BULT

STORAGE

TANKS

MUD

TANKS

PADDLE

AGITATORS

SUCTION

LINE

RESERVE

TANKS

DESANDER

(DESILTER)

MUD MIXING

HOPPER

• Drilling fluid returning from the well bore contains drilled cuttings, sand, and other particles from the hole.

• This solid material must be removed before the fluid is returned to circulation.

• If the drilling fluid is low-viscosity mud, a large settling pit can be used to cause most of the solids to settle out by gravity separation.

• But a more satisfactory arrangement is to use high-capacity vibration screen shakers for screening the large particles, and sometimes small ones, also.

• The screened mud then flows into the mud tanks for further conditioning prior to being pumped back into the well.

• The material that remains on top of the screening surface is the oversized material; the material passing through the screen is the undersized material. – The most commonly used shaker screens have relatively

large openings for removing large cuttings

– Since many fine particles adhere to the coarser ones and are therefore discharged, a spray of water should not be used on the shaker screen if the maximum amount of drilled material is to go to waste.

• The solids in mud can be divided into two groups:

(1) low gravity (drill solids and bentonite; density around 2600 kg�m-3) and

(2) high gravity (barite; density 4200 kg�m-3).

• The low gravity solids are further divided into nonreactive and reactive groups.

– Nonreactive solids consist of sand, chert, limestone, dolomite, some shales and mixture of many minerals.

– When larger of 10 to 15 micrometers they can be abrasive to pump parts.

Shale shakers

• The material that remains on the top of the screen surface is the oversized material; and those passing through is undersized material.

• The sand trap compartment below vibrating screen shale shaker is used to catch the larger particles passing over screens or holes in it.

• The bottom of the sand trap should be sloped so that the particles settle toward the cleanout openings.

• High-capacity vibrating screen shakers are used for screening the larger particles, and sometimes small ones, also.

Sizes of solids and shaker screen

• All materials not passing through 74 micrometerscreen openings, are classed as sand, regardless of their nature.

• Below 200 mesh (or 74 micrometers) particles are classed as silt or colloid.

PARTICLE SIZE

SCREEN

OPENINGS micrometer inch

1540 0,0606 12x12 1230 0,0483 14x14 1020 0,0403 16x16 920 0,0362 18x18 765 0,0303 20x20

SCREENS FOR LABORATORY

TESTING

210 0,00827 U.S.S number 60 147 0,00579 U.S.S. number 100 74 0,00291 U.S.S. number 200

Desanders or desilters

• A whirling motion is impaired to the fluid, much like that of a water spout. – A short pipe, called a vortex finder, extends down into the cone body from the top.

– It forces the whirling stream to start downward toward the small end of the cone body.

– The larger, heavier particles are thrown outward toward the wall of the cone, while the finer, lighter particles, which move outward more slowly, are not separated but remain as part of the fluid mud.

– The larger particles and a small amount of fluid move to the bottom of the cone and pass out through the apex.

– The remainder of fluid, containing small particles, reverses direction and passes back up inside the cone of fluid, leaving by way of the vortex finder.

Liquid discharge

Vortex

finder

Inlet

Adjustable valve or

variable openning

Solids discharge

Apex

(1) Pressurized

slurry enters

tangentially

(2) Slurry rotation

develops high

centrifugal forces

(3) Liquid moves

inward and upward

as spiral vortex

(4) Suspended

solids are driven

toward wall and

downward in

accelerating

spiral

• Pressure is a critical factor in obtaining maximum efficiency in desanding and desilting with cone-shaped centrifuges.

• If the pressure is not sufficient, solids do not separate well from mud.

• If there is too much pressure, the service life of the units is drastically reduced. – Most desanders operate at

about 2,4�105 Pa (35 psi), and most desilters at 3,1�105 Pa (45 psi); measured at the equipment (not at the pump).

DESANDER DESILTERBARITE

SALVAGE

FEED

DISCARD DISCARD SAVE

SAVE SAVE DISCARD

Desanders

• A hydro cyclone, or cone-shaped centrifugal separator, that has no moving parts with diameter of 152,4 mm (6") to 304,8 mm (12”).

• It imparts a whirling motion to the fluid sent through it thereby activating sufficient centrifugal force to separate various particle size.

Although not greatly efficient, it is fairly simple and inexpensive to operate and has a relatively high capacity.

They should be fed with centrifugal pump to obtain steady pressure.

Desilters

• Good desilters, properly operated, reject all material of sand size, a high percent of solids larger than 10 to 20 micrometers and decreasing percentage of materials down to 2 to 3 micrometers.

• Desilters used for drilling mud have cones of 76,2 mm (3”), 101,6 mm (4”) or 127,0 mm (5”) diameter, and the number depends on the amount of total fluid that is circulated in the well.

•Desilters should be run at all times when unweighted water-base muds are used.

•They prepare the system by removing a large percentage of undesirable drilling solids.

•The best location for a desilter is where it will take suction downstream from the shale shaker and the desander.

Mud cleaners

• They use a combination of desilting hydrocyclones and a very fine mesh vibrating screen to remove drilled solids while returning valuable mud additives and liquids back to the active mud system.

• After the drilling fluid has passed through a shale shaker to remove large cuttings, the mud is pumped into the cyclones on the mud cleaner. – They clean the mud and discharge

the fine solids and the liquid phase into next tank downstream.

– The solids discharged are deposited onto the fine screen mounted below.

– Drill solids larger than the screen openings are discharged to a waste pit, and the solids small enough to pass through the screen and the liquid film around them are discharged into the next tank downstream.

– The size of the particles separated by a mud cleaner depends on the efficiency of the desilting cones and the mesh of the screen.

Feed manifold

Mud from

hole

Drilled solids

discharge

spout

Oversized

particles

Waste pit

Discharge

manifoldUndersized

particles and

liquid

Hydrocyclones

Barite and

liquid

discharge

spout

Medium-sized

particles

Pit or

compartment

Screen holes

Screen surface

Overflow ells

Decanting

centrifuge

• Decanting centrifuge is used primarily with weighted muds to recover weighting materials and reject viscosity-producing fines(size 2 to 5 micrometers).

– It is very efficient and is capable of making a sharp cut of fine material, depending on the density of the solids.

– Thus it is very useful as a super-desilter to remove drilled solids from unweighted oil-base muds, since it discards the coarse solids as a semidry sludge with minimum loss of the valuable liquid phase.

– When a weighted mud is being processed to remove and save a barite, the mud is diluted with water as it enters the machine, to reduce viscosity and allow efficient separation of solids.

Degassers

• Gas and mud flowing from a well during a kick can be very dangerous.

• The gas must be vented at a safe distance from the well, and the liquid mud should be returned to the mud tanks to prevent waste.

• Several types of degassers may be employed:– mud-gas separators,

– vacuum degassers, and

– others.

Mud-gas

separators

• They consist a vertical vessel arranged to vent free gas from the upper end and discharge less foamy mud from the bottom. – Free gas from the mud is

taken from the separator through the pipe connection near the top of the unit and led off to a point where it can be safely vented or flared.

– Liquid mud is taken from the unit near the lower end, then through a riser and horizontal line to the shale shaker and mud tanks.

– Working pressure of the separator is up to 6,89�105 Pa (100 psi).

• Standard production separator can be used as well.

• The idea is to allow fluid to flow and disperse over the plates due the gravitation and so help the gas to leave the fluid.

1) Feed in flange

2) Feed in line

3) Scatterer

4) Scatterer pipe

5) Scatterer plates

6) Discharge line

Vacuum degassers

• Mud enters the degasser through an riser pipe at the right end of the machine because vacuum is applied to the vapor space of the vessel by the vacuum pump mounted on the unit. – The top of the pipe is sliced away in a horizontal plane so that the

mud can spill over the sides and down an inclined plane extending the full length of the feed pipe and sloping downward.

– As the mud streams down the inclined plane, the vacuum in the vapor space causes the gases to leave the mud and to be withdrawn from the tank by the vacuum pump.

– The degassed mud flows to the bottom of the vessel for exit. – The mud flows from the bottom of the vessel through the tube at the

left of the machine into the second mud tank. – S hydraulically operated jet is located in this downspot.

• Mud at high velocity is pumped through this jet to lower the mudpressure here below the mud pressure in the degasser.

• In this way the mud is made to flow from the degasser in spite of the vacuum in it.

• The mud enters the degasser through the pipe of 203,2 mm (8”) diameter, on the right side, because of the under-pressure due the work of vacuum pump.

• There is a vacuum of 0,22�105 to 0,41�105 Pa depending on the mud density.

• Degasser my handle mud containing lost circulation material at circulation rates exceeding 2,27 m3 of mud in the minute.

• It is more effective for thin mud than for thick.

(1) connection, (2) valve, (3) and (6) manometers, (4) level control, (5) wash out connection, (7) water catcher, (8) vacuum pump, (9) and (16) connecting elements, (10) chock valve, (11) water wash down plug, (12) mud wash down plug, (13) feed in, (14) buoy, (15) ejecting line connection, (17) and (18) ejecting line, (19) pressure line, (20) degasser house

System of gas separation

MUD WITH GAS + FREE GAS

MUD WITH GAS

CLEAN MUD

GAS

FREE

GAS

TO THE

FLARE

CHOOKE

MANIFOLD

VIBRATOR

GAS

SEPARATION

Jet hopper

• The principle of the venturi tube downstream from the jet nozzle makes

mixing effective .

– The principle is that, as velocity of the fluid flow is increased through the construction, the pressure is decreased.

– The butterfly valve used between the hopper and the jet-nozzle housing should be kept close while mixing is not in progress to minimize aeration of the fluid passing through the mixer.

– The high fluid velocity through the nozzle lowers the static pressure in the housing to below atmospheric-that is, a vacuum is created, and therefore material placed in the hopper is sucked into the stream of fluid, where it becomes mixed with the fluid.

CENTRIFUGAL

PUMP

BUTTERFLY

VALVE

VENTURI PIPE

MIXING HOPPER

Jet siphon • Jet siphons are used for transferring mud, sand, or cuttings from a mud tank to reserve pit.

– They use regular drilling mud or water pumped through the smaller pipe to stuck fluid into the larger pipe for removal from the tank.