Drilling Engineering – Fall 2012 Prepared by: Tan Nguyen Drilling Engineering – PE311...

Drilling Engineering – Fall 2012

Prepared by: Tan Nguyen

Drilling Engineering – PE311

Circulating System



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.

Circulating System in Drilling



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.

Auxiliary System

Drilling fluid maintenance system



Shale Shaker

Auxiliary 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.

Auxiliary System




http://www.youtube.com/watch?v=82VXx-tEpnQ

Auxiliary 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.

Auxiliary System

Well pressure control system



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.

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

BOPs



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.

Mud Pumps



Triplex pumps have three cylinders, and are generally single-acting pumps

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.

Triplex Pumps – 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

p, psi and Q, GPM

Pump Factor – Single acting

dr



Duplex Pumps – Double Acting

Duplex pumps have two cylinders, and are generally double-acting pumps



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.

Duplex Pumps – 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

Pump Factor – Double Acting



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

Example



1. Pump factor in units of gal/cycle at 100% volumetric efficiency

2. Flow rate in gal/min

3. Pump power developed

Example

Drilling Engineering – Fall 2012 Prepared by: Tan Nguyen Drilling Engineering – PE311...

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