Q922+de1+l03 v1

Drilling Engineering 1 Course (2nd Ed.)

1. Introduction
2. Personnel at Rig Site
3. Rotary Drilling System

1. Power System
2. Hoisting System:
A. Introduction
B. The Block & Tackle
a.

Mechanical advantage and Efficiency

power supply
The power system of a rotary drilling rig has to
supply power to all the other systems.
the system must provide power for
pumps in general, rig light, air compressors, etc.

Since the largest power consumers on a rotary drilling
rig are
the hoisting, the circulation system, and the rotary system,
these components determine mainly the total power
requirements.

During typical drilling operations,
the hoisting and the rotary systems are not operated
at the same time. Therefore the same engines can be used to
perform both functions.
Spring14 H. AlamiNia


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power system
Drilling rig power systems are classified
as direct drive type (internal combustion engines supply
mechanical power to the rig )
and electric type.

In both cases,
the sources of energy are diesel fueled engines.

Most rigs use
1 to 3 engines to power the drawworks and rotary table.

The engines are usually rated between 400 and 800 hp.
As guideline, power requirements
for most onshore rigs are between 1,000 to 3,000 hp.
Offshore rigs in general use much more power.


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power system performance
The performance of a rig power system is
characterized by
the output horsepower,
torque,
and fuel consumption for various engine speeds.

These three parameters are related by the
efficiency of each system.



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energy consumption by the engines
 The energy consumed by the engines comes
from burning fuels.
 The engine transforms the chemical energy
of the fuel into work.

Heating
values of fuels
Heating
Density
Fuel Type Value
(lbm/gal)
(BTU/lbm)
Diesel
19000
7.2
Gasoline 20000
6.6
Butane
21000
4.7
(liquid)
Methane
–
24000
(gas)

 No engine can transform totally the chemical
energy into work.
 Most of the energy that enters the engine is
lost as heat.

 The thermal efficiency Et of a machine is
defined as the ratio of the work W
generated to the chemical energy consumed

 to perform this calculation, we must use the
same units both to the work and to the
chemical energy.
 1 BTU = 778.17 lbf/ft,



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thermal efficiency
Engines are normally rated by the power P
they can deliver at a given working regime.
Power if defined as the rate work is performed,
that is work per unit of time.
If ˙Q is the rate of chemical energy consumed by the machine
(chemical energy per unit of time),
we can rewrite the expression for the thermal efficiency as:

To calculate ˙Q we need to know the type of fuel and
the rate of fuel consumption in mass per unit time.
Consumption of gaseous fuels is given in mass per unit time.
consumption for liquid fuels is given in volume per unit time.
we need to know the density of the fluid.


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output power
A system produces mechanical work when the sole
result of the process could be the raising of a weight
(most time limited by its efficiency).
P is power, and v the velocity (assuming F constant).

When a rotating machine is operating (for example,
an internal combustion engine or an electrical motor),
we cannot measure its power,
but we can measure its rotating speed (normally in RPM) and
the torque at the shaft.
This is normally performed in a machine called dynamometer.


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output power
The expression relating power to angular velocity
and torque is:
ω is the angular velocity (in radians per unit of time)
T is the torque.

A common unit of power is the hp (horse power).
One hp is the power required
to raise a weight of 33,000 lbf by one foot in one minute:



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output power
For T in ft lbf and N in RPM we have:

that is



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mechanical horsepower Correction
When the rig is operated
at environments with non–standard temperatures
(85F=29C) or
at high altitudes,
the mechanical horsepower requirements
have to be corrected.
The correction should follow
the American Petroleum Institute (API) standard 7B-llC:
Deduction of 3% of the standard brake horsepower for each
1000 ft of altitude above mean sea level.
Deduction of 1% of the standard brake horsepower for each
10F rise or fall in temperature above or below 85F.


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Calculation of the output power
and the overall efficiency
A diesel engine gives
an output torque of 1740 ft lbf
at an engine speed of 1200 RPM.
 If the fuel consumption rate was 31.5 gal/hr,
what is the output power and
the overall efficiency of the engine?



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the output power and
the overall efficiency
The power delivered at the given regime is:

Diesel is consumed at 31.5 gal/hr. From Table we have:

Converting to hp, results in:

The thermal efficiency is:


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Typical hoisting system
The hoisting system is used
to raise, lower, and suspend
equipment in the well
 (e.g., drillstring, casing, etc).

It is consists of:
 derrick (not shown)
 draw works
 the block-tackle system
 fast line (braided steel cable)
 crown block
 traveling block
 dead line (1” to 13/4=3.25”)
 deal line anchor,
 storage reel,
 hook.



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The Derrick
The derrick or mast is a steel tower.
If the tower is jacked up, it is called mast.
If the tower is erected on the site, it is called derrick.

Derricks are rated by the API according
to their height (to handle 2, 3, or 4 joints) and
their ability to withstand wind and compressive loads.

The derrick stands above the derrick floor.
The derrick floor is the stage where several surface drilling
operations occur. At the derrick floor are located
the drawworks, the driller’s console, the driller’s house (or
“doghouse”), the rotary table, the drilling fluid manifold, and
several other tools to operate the drillstring.

The space below the derrick floor is the substructure.


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Substructure and Monkey Board
The height of the substructure
should be enough to
accommodate the well control
equipment.
At about 3/4 of the height of the
derrick is located a platform called
“monkey board”.
This platform is used to operate the
drillstring stands during trip
operations.
During drillstring trips, the stands are
kept stood in in the mast, held by
“fingers” in the derrick rack near the
monkey board.
Stand of doubles



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drawworks
The drawworks provides
hoisting and
braking power
required
to handle the heavy
equipment in the borehole.
It is composed of
 a wire rope drum,
 mechanical and
hydraulic brakes,
 the transmission,
 and the cathead

 (small winches operated by
hand or remotely to provide
hoisting and pulling power to
operate small loads and
tools in the derrick area).
a typical onshore rig drawworks



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Reeling in and out
The reeling–in of the drilling line
is powered by an electric motor or Diesel engine

the reeling–out
is powered by gravity
To control the reeling out,
mechanical brakes and
auxiliary hydraulic or magnetic brakes

are used, which dissipates the energy required to reduce
the speed and/or stop the downward movement of the
suspended equipment.



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Brake belts and magnification linkage
of drawworks



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Drawworks schematics
 The drawworks take
power from Diesel
engines or electrical
motors, and an
assembly of gears
and clutches
reduces the rotary
speed to power the
drum and the
various catheads.
 the drum surface
has a helical groove
 to accommodate
the drilling line
without causing
excessive stress
and stain.
 helps the drilling
line to lay neatly
when reeled in



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The Block & Tackle
Fast line

 The drilling line coming from the drawworks, called fast line, goes
over a pulley system mounted at the top of the derrick,
 called the crown block,

 and down to another pulley system
 called the traveling block.

block-tackle

 The assembly of crown block, traveling block and drilling line

The number of lines n of a tackle

 is twice the number of (active) pulleys in the traveling block.

The last line of the tackle

 is called dead line
 and is anchored to the derrick floor, close to one of its legs.

Below and connected to the traveling block is a hook to
which drilling equipment can be hung.


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block-tackle system calculations
The block-tackle system
provides a mechanical advantage to the drawworks, and
reduces the total load applied to the derrick.

We will be interested in calculating
the fast line force Ff (provided by the drawworks)
required to raise a weight W in the hook, and
the total load applied to the rig and
its distribution on the derrick floor.



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Forces acting in the block–tackle



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Ideal Mechanical advantage
The mechanical advantage AM of the block–tackle
is defined as the ratio of the load W in the hook
to the tensile force on the fast line Ff :

For an ideal, frictionless system,
the tension in the drilling line
is the same throughout the system, so that W = n Ff .
Therefore, the ideal mechanical advantage is equal to
the number of lines strung through the traveling block:



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efficiency of a real pulley
In a real pulley, however, the tensile forces in the
cable or rope in a pulley are not identical.
If Fi and Fo are the input and output tensile forces of the
rope in the pulley, the efficiency of a real pulley is given
by the following ratio:

We will assume that all pulleys in the hoisting
system have the same efficiency, and we want to
calculate the mechanical advantage of a real pulley
system.


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total load W
If Ff is the force in the fast line, the force F1 in the
line over the first pulley (in the crown block) is
given by
The force in the line over the second pulley (in the
traveling block) is
Using the same reasoning over and over, the force
in the ith line is
The total load W acting in the hook is equal to the
sum of the forces in each line of the traveling block.



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Block–tackle overall efficiency
AM=the real mechanical advantage
The overall efficiency E of the system
of pulleys is defined as the ratio of
the real mechanical advantage to the
ideal mechanical advantage
A typical value for the efficiency of
ball–bearing pulleys is = 0.96.
Table shows the calculated and
industry average overall efficiency for
the usual number of lines.
if E is known, the fast line force Ff
required to rise a load W can be
calculated


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1. Jorge H.B. Sampaio Jr. “Drilling Engineering
Fundamentals.” Master of Petroleum
Engineering. Curtin University of Technology,
2007. Chapter 2

1. Hoisting System:
A. The Block & Tackle
a.

Hook Power

B. Load Applied to the Derrick

2. Drilling Fluid Circulation System
A. Mud Pumps

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