Lyons W.C. (ed.). Standard handbook of petroleum and natural gas engineering.2001- Volume 1
Подождите немного. Документ загружается.
Rotary
Equipment
625
KELLY SQUARE
DRIVE BUSHING REMOVED
FROM TABLE
9"
27'
45",
+
2
30"
CUT-AWAY SHOWING
MASTER BUSHING
Figure 4-96.
Rotary table with square drive bushings and slips
[13].
Figure 4-97.
m+A
-4
Rotary table opening and square drive master bushing
[13].
626
Drilling and Well Completions
1
I
PIN
DRIVE
KELLY
BUSHING
9"
27'
45"
f
2'
30"
(7-131
PIN
DRIVE
MASTER
BUSHING
Figure
4-98.
Pin-drive master bushing
[13].
(text
continued
from
page
623)
The
API
requirements for rotary table openings for square drive master bushings
and the sizes of the square drive and pin-drive master bushings are specified in
API
Specification
7
[l].
Kelly
Bushings
The kelly bushing attaches the kelly to the rotary table.
It
locks into the master
bushing and transfers the torque produced by the table to the kelly. There are
two types of kelly bushings
[16]:
1.
Square drive kelly bushings (aligned with square drive master bushings)
2.
Pin drive kelly bushings (aligned with pin-drive master bushings)
Mud Pumps
627
MUD PUMPS
Mud pumps consume more than
60%
of all the horsepower used in rotary
drilling. Mud pumps are used to circulate drilling fluid through the mud circulation
system while drilling. A pump with two fluid cylinders, as shown in Figure
4-99,
is
called a duplex pump. A three-fluid-cylinder pump, as shown in Figure
4-100,
is called a triplex pump. Duplex pumps are usually double action, and triplex
pumps are usually single action.
Mud pumps consist of a power input end and a fluid output end. The power
input end, shown in Figure
4-101,
transfers power from the driving engine
(usually diesel or electric) to the pump crankshaft. The fluid end does the actual
work of pumping the fluid.
A
cross-section of the fluid end is shown in
Figure
4-102.
Pump Installation
Suction Manifold
The hydraulic horsepower produced by mud pumps depends mainly on the
geometric and mechanical arrangement of the suction piping. If suction-charging
centrifugal pumps (e.g., auxiliary pumps that help move the mud to the mud
pump) are not used, the pump cylinders have to be filled by the hydrostatic head.
Incomplete filling of the cylinders can result in hammering, which produces
destructive pressure peaks and shortens the pump life. Filling problems become
more important with higher piston velocities. The suction pressure loss through
the suction valve and seat is from
5
to
10
psi. Approximately
1.5
psi of pressure
is required for each foot of suction lift. Since the maximum available atmospheric
pressure is
14.7
psi (sea level), suction pits placed below the pump should be
Figure
4-99.
Duplex slush (mud) pump.
(Courtesy
National
Oilwell.)
628
Drilling and Well Completions
Figure
4-100.
Triplex slush (mud) pump.
(Courtesy National
Oilwell.)
Figure
4-101. Power end
of
mud pump.
(Courtesy
LTV
Energy Products
Company.)
Mud Pumps
629
eliminated. Instead, suction tanks placed level with or higher than the pump
should be used to ensure a positive suction head. Figure
4-103
shows an ideal
suction arrangement with the least amount of friction and low inertia.
A
poorly designed suction entrance to the pump can produce friction equiva-
lent to
30
ft of pipe. Factors contributing to excessive suction pipe friction are
an intake connection with sharp ends, a suction strainer, suction pipe with a
small diameter, long runs
of
suction pipe, and numerous fittings along the
Figure
4-102.
Cross-section of fluid end of mud pump.
(Courtesy
International Association
of
Drilling Contractors.)
SHORT
AND
DIRECT
___
WITH
NO
TURNS
SAME
SIZE
AS
Figure
4-1
03.
Installation
of
mud pump suction piping.
(Courtesy International
Association
of
Drilling Contractors.)
630
Drilling and Well Completions
suction pipe. Minimizing the effect
of
inertia requires a reduction of the suction
velocity and mud weight. It is generally practical to use a short suction pipe
with a large diameter.
When a desirable suction condition cannot be attained, a charging pump
becomes necessary. This is a common solution used on many modern rigs.
Cooling
Mud
Mud temperatures of
150'
can present critical suction problems. Under
low
pressure
or
vacuum existing in the cylinder on the suction stroke, the mud can
boil, hence decreasing
the
suction effectiveness. Furthermore, hot mud accelerates
the deterioration of rubber parts, particularly when oil is present. Large mud
tanks with cooling surfaces usually solve the problem.
Gas and Air Separation
Entrained gas and air expands under the reduced pressure of the suction
stroke, lowering the suction efficiency, Gas in water-base mud may also deteriorate
the natural rubber parts used. Gases are usually separated with baffles or by
changing mud composition.
Settling Pits
The normally good lubricating qualities of mud can be lost if cuttings,
particularly fine sand, are not effectively separated from the mud. Adequate
settling pits and shale shakers usually eliminate this trouble. Desanders are
used occasionally.
Discharge Manifold
A poorly designed discharge manifold can cause shock waves and excessive
pressure peaks. This manifold should be as short and direct as possible, avoiding
any sharps turns. The conventional small atmospheric air chamber, often
furnished with pumps, supplies only
a
moderate cushioning effect. For best
results, this air chamber should be supplemented by a large atmospheric air
chamber or by a precharged pulsation dampener.
Pump Operation
Priming
A
few strokes of the piston in a
dry
liner may ruin the liner. When the pump
does not fill by gravity or when the cylinders have been emptied by standing
too long
or
by replacement of the piston and liner, it is essential to prime the
pump through the suction valve cap openings.
Cleaning the Suction Manifold
Suction lines are often partly filled by settled sand and by debris from the
pits, causing the pump to hammer
at
abnormally low speeds. Frequent inspection
and cleaning of the suction manifold
is
required. The suction strainer can also
be a liability if
it
is not cleaned frequently.
Mud Pumps
631
Cleaning the Discharge Strainer
The discharge strainer often becomes clogged with pieces
of
piston and valve
rubber. This may increase the pump pressure that is not shown by the pressure
gauge beyond the strainer. The strainer should be inspected and cleaned
frequently to prevent a pressure buildup.
Lost Circulation Materials
Usually special solids, such as nut shells, limestone, expanded perlite, etc.,
are added to the drilling muds to fill
or
clog rock fractures in the open hole
of a well. Most of these lost circulation materials can shorten the life of pump
parts. They are especially hard on valves and seats when they accumulate on
the seats
or
between the valve
body
and the valve disc.
Parts Storage
Pump parts for high-pressure service are made of precisely manufactured
materials and should be treated accordingly. In storage at the rig, metal parts
should be protected from rusting and physical damage, and rubber parts should
be protected from distortion and from exposure to heat, light, and oil. In
general, parts should remain in their original packages where they are usually
protected with rust-inhibiting coatings and wrappings and
are
properly supported
to avoid damage. Careless stacking of pistons may distort
or
cut the sealing lips
and result in early failures. Hanging lip-type
or
O-ring packings on a hook or
throwing them carelessly into a bin may ruin them. Metal parts temporarily removed
from pumps should be thoroughly cleaned, greased, and stored like new parts.
Pump Performance Charts
The charts showing the performance of duplex pumps are shown in Table
4-38
[17].
The charts showing the performance of triplex pumps are shown in Table
4-39
[17].
A
chart listing the pump output required for a given annular velocity
is shown
in
Table
4-40
[18].
A
chart listing the power input horsepower required
for a given pump working pressure is shown in Table
441 [19].
Mud Pump Hydraulics
The required pump output can be approximated as follows
[20-221:
Minimum
Q
(gal/min):
Qi,
=
(30
to
50)
D,
or
where
D,
=
hole diameter in
in.
D
=
pipe diameter in in.
$
=
mud specific weight in lb/gal
(4-36)
(4-34)
(text
continued
on
pagp
644)
Table
4-38
Mud Pump Performance-Duplex Pumps
[17]
Pump Discharge Pressure (PSI) (Shaded Area);
Pump Discharge Volume (GalJStroke) (Based on
100%
Volumetric Efficieny)
a
E
-
Q,
w
w
Table
4-38
(continued)
NAWfACNWR
COWIINEWAL
EYSCO(DVPLOO
I
IYFR
SIIF
IINI
I
I
I
I
C-loo0
1wO
60
18'
3'
DC.Ioo0
OEIWO
1
1187
7Q
18''
3"
I I
I
I
I
I I
I I
b13S
1575
70
18' 3-112"
I
C-1650
1925
70
18"
3.1/2"
DC.16sO