Drilling Engineering – Fall 2012
Drilling Engineering – PE311
Circulating System
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Circulating System in Drilling
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Circulating System in Drilling
The drilling mud travels up the stand pipe and through the rotary hose, and then
downward through the kelly or top drive system, drill pipe and bottomhole assembly
by the mud pumps. It exists the drill string through the bit nozzles and picks up drill
cuttings from the bottom of the hole. It then carries the cuttings up the annulus, past
the blowout preventers, and through the mud-return line to the shale shaker. At the
shale shaker, the larger cuttings are screened out and diverted to a "reserve pit"
(actually a waste pit). Desanders, desilters and centrifuges may be used to filter out
smaller particles. The mud flows into a settling tank or pit and finally, it returns
through the sump to the suction pit to repeat the circuit.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Auxiliary System
Drilling fluid maintenance system
There are two types of auxiliary systems associated with the basic circulating
system: the drilling fluid maintenance system and the well pressure control system.
The drilling fluid maintenance system includes the shale shaker (a set of rotating or
vibrating screens, which removes the larger drill cuttings from the returning mud and
serves as the sampling point for drill-cuttings analysis); mud guns and mud-pit
agitators for maintaining a uniform content of mud solids; cone-type desanders,
desilters, and centrifuges to remove contaminants that would not otherwise settle
out; and a mud-gas separator and vacuum degasser for removal of entrained gases.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Auxiliary System
Drilling fluid maintenance system
Shale Shaker
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Auxiliary System
Drilling fluid maintenance system
Desilters and Desanders: The desilters/desanders must be equipped with
centrifugal pumps capable of providing sufficient pressure to the hydrocyclones to
allow them to operate in the desired pressure range.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Auxiliary System
Drilling fluid maintenance system
http://www.youtube.com/watch?v=82VXx-tEpnQ
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Auxiliary System
Well pressure control system
The main components of the well pressure
control system is the blowout preventers
(BOPs), which are located under the rig
floor on the casing head. A blowout
preventer is a large, specialized valve
used to seal, control and monitor oil and
gas
wells.
Blowout
preventers
were
developed to cope with extreme erratic
pressures
and
uncontrolled
flow
emanating from a well reservoir during
drilling.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
BOPs
A ram-type BOP uses a pair of opposing steel
plungers, rams. The rams extend toward the
center of the wellbore to restrict flow or retract
open in order to permit flow. The inner and top
faces of the rams are fitted with packers
(elastomeric seals) that press against each
other, against the wellbore, and around tubing
running through the wellbore. Outlets at the
sides of the BOP housing (body) are used for
connection to choke and kill lines or valves.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
BOPs
Pipe rams (Annular preventer) close around a drill
pipe, restricting flow in the annulus between the
outside of the drill pipe and the wellbore, but do not
obstruct flow within the drill pipe.
Blind rams which have no openings for tubing, can
close off the well when the well does not contain a
drill string or other tubing, and seal it.
Shear rams cut through the drill string or casing with
hardened steel shears.
Kill line: permits mud to be pumped down to the
annulus to restore a pressure balance
Choke line: Annular pressure relief lines
http://www.youtube.com/watch?v=kBQdTv7bspM
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Mud Pumps
The mud pumps are the heart of the
circulating system, providing power
to move the fluid at the required
pressure and volume. Mud pumps
are either duplex (two-cylinder) or
triplex
(three-cylinder).
Triplex
pumps are by far the type most
commonly used on modern rigs.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Triplex Pumps – Single Acting
Triplex pumps have three cylinders, and are generally single-acting pumps
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Triplex Pumps – Single Acting
As the plunger (A) moves to the right, the fluid is compressed until its pressure exceeds the
discharge pressure, and the discharge check valve (B) opens.
The continued movement of the plunger to the right pushes liquid into the discharge pipe.
As the plunger begins to move to the left, the pressure in the cylinder becomes less than that
in the discharge pipe, and the discharge valve (B) closes.
Further movement to the left causes the pressure in the cylinder to continue to decline until it
is below suction pressure. At this point the suction check valve (C) opens.
As the plunger continues to move to the left, the cylinder fills with liquid from the suction.
As soon as the plunger begins to move to the right, it compresses the liquid to a high enough
pressure to close the suction valve (C), and the cycle is repeated.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Pump Factor – Single acting
The volume displaced by each piston during one complete pump cycle is given by
The pump factor for a single-acting pump having three cylinders becomes
The flow rate
Where N is the number of
stroke per unit time
Hydraulic power
Dp, psi and Q, GPM
Prepared by: Tan Nguyen
dr
Drilling Engineering – Fall 2012
Duplex Pumps – Double Acting
Duplex pumps have two cylinders, and are generally double-acting pumps
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Duplex Pumps – Double Acting
Duplex pumps are double-acting, with two cylinders. Each of the two cylinders is
filled on one side of the piston at the same time that fluid is being discharged on the
other side of the piston. With each complete cycle of a piston, mud is discharged at
twice the volume of the cylinder minus the volume of the piston rod.
When the piston moves to the right, the liquid in the cylinder to the right of the piston
(E) is discharged, and the cylinder to the left of the piston (F) is filled.
When the direction of the piston is reversed, the liquid in F is discharged, and the
cylinder at E is filled with suction fluid.
Thus, liquid is pumped when the piston moves in either direction.
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Pump Factor – Double Acting
On the forward stroke of each piston, the volume displaced is given by
On the backward stroke of each piston, the volume displaced is given by
Thus, the total volume displaced per complete pump cycle by a pump having two
cylinders is given by
The flow rate
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Example
Consider a triplex pump having 6-in liners and 11-in strokes operating at 120
cycles/min and a discharge pressure of 3000 psig. Compute
1. Pump factor in units of gal/cycle at 100% volumetric efficiency
2. Flow rate in gal/min
3. Pump power developed
Prepared by: Tan Nguyen
Drilling Engineering – Fall 2012
Example
1. Pump factor in units of gal/cycle at 100% volumetric efficiency
2.
Flow rate in gal/min
3.
Pump power developed
Prepared by: Tan Nguyen