q921 de1 lec 3 v1

Drilling Engineering 1 Course (1st Ed.)

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http://www.about.me/AlamiNia

mailto:[email protected]

http://www.about.me/AlamiNia

1. Introduction

2. Personnel at Rig Site

3. Rotary Drilling System

1. Power System

2. Hoisting System:A. Introduction

B. The Block & Tacklea. 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.

Fall 13 H. AlamiNia Drilling Engineering 1 Course: 5

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.


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.


energy consumption by the engines

Heating values of fuels

The energy consumed by the engines comes from burning fuels.

The engine transforms the chemical energy of the fuel into work. 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,


Fuel TypeHeating

Value(BTU/lbm)

Density(lbm/gal)

Diesel 19000 7.2

Gasoline 20000 6.6

Butane (liquid)

21000 4.7

Methane (gas)

24000 –

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.


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.


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:


output power

For T in ft lbf and N in RPM we have:

that is


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.


Calculation of the output power and the overall efficiency

A diesel engine gives an output torque of 1740 ft lbfat 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?


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:


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.


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.


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 doublesFall 13 H. AlamiNia Drilling Engineering 1 Course: 20

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 drawworksFall 13 H. AlamiNia Drilling Engineering 1 Course: 21

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.


Brake belts and magnification linkage of drawworks


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


The Block & Tackle

Fast lineThe 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.


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.


Forces acting in the block–tackle


Ideal Mechanical advantage

The mechanical advantage AM of the block–tackleis 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:


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.


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.


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


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

q921 de1 lec 3 v1

Technology

output power

mechanical power

power supply

power p

power system performance

common unit of power

alaminiadrilling engineering

total power requirements