Hatem Naga Training Book - Heavy Oil

7/29/2019 Hatem Naga Training Book - Heavy Oil

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Table of Contents

1.1.HISTORY ................................................................................................................................ 1

OPEC .......................................................................................................................................... 1

FOUNDATION OF OPEC ............................................................................................................... 1

OPEC MISSION ............................................................................................................................ 1

STATISTICS ON THE WORLD CURRENT CRUDE OIL RESERVES ....................................................... 2

1.2.GEOLOGY .............................................................................................................................. 3

ROCKCHARACTERISTICS ............................................................................................................. 3

Porosity ................................................................................................................................... 3

Permeability ............................................................................................................................ 3

EXPLORATION OF HYDROCARBONS ............................................................................................. 4

Exploration methods ............................................................................................................... 4

Exploration risk ...................................................................................................................... 4

1.3.RESERVOIRS ....................................................................................................................... 5

DEFINITION .................................................................................................................................. 5OIL TRAPS .................................................................................................................................... 5

DRIVE MECHANISM ...................................................................................................................... 6

1.4.OVERVIEW ON DRILLING RIGS ................................................................................... 7

DEFINITION .................................................................................................................................. 7

TYPE OF RIGS ............................................................................................................................... 7

Offshore-based drilling rigs .................................................................................................... 7

Onshore-based drilling rigs .................................................................................................... 9

RIG PERSONNEL ......................................................................................................................... 10

RIG COMPONENTS ..................................................................................................................... 11

DRILLING RIG SCHEMATIC......................................................................................................... 12


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1.5.WELL COMPLETION ...................................................................................................... 15

CASING ...................................................................................................................................... 15

Function of Casing ................................................................................................................ 15

Types of Casing ..................................................................................................................... 16CEMENTING ............................................................................................................................... 18

Definition .............................................................................................................................. 18

Function of Cementing .......................................................................................................... 18

COMPLETING THE WELL ............................................................................................................. 18

2.1.ARTIFICIAL LIFT SYSTEMS ......................................................................................... 19

DEFINITION ................................................................................................................................ 19

PURPOSE OF ALS ....................................................................................................................... 19

2.2.OIL-WELL BEHAVIOR.................................................................................................... 20

OVERVIEW ON MOST WELLS BEHAVIOR.................................................................................... 20

DECLINE CURVE ........................................................................................................................ 20

2.3.ENHANCED OIL RECOVERY ........................................................................................ 21

DEFINITION ................................................................................................................................ 21

CLASSIFICATIONS OF

EORT

ECHNIQUES.................................................................................... 21

2.4.TYPES OF ARTIFICIAL LIFT SYSTEMS..................................................................... 22

SUCKERROD PUMP.................................................................................................................... 23

PROGRESSIVE CAVITY PUMP (PCP) ........................................................................................... 26

ELECTRIC SUBMERSIBLE PUMP (ESP) ........................................................................................ 28

SUBSURFACE HYDRAULIC PUMP ................................................................................................ 30

GAS LIFT .................................................................................................................................... 33

2.5.SELECTING AN ARTIFICIAL LIFT METHOD .......................................................... 35

3.1.OVERVIEW ON HEAVY OIL.......................................................................................... 37

DEFINITION ................................................................................................................................ 37

CLASSIFICATION OF OIL TYPES.................................................................................................. 37

REASONS OF STRONG DEMAND ON HEAVY OIL .......................................................................... 38


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3.2.HEAVY OIL PRODUCTION ............................................................................................ 39

HEAVY OIL PRODUCTION TECHNIQUES ..................................................................................... 39

Thermal Recovery Techniques .............................................................................................. 40

Emerging Techniques............................................................................................................ 42

3.3.OVERVIEW ON WEATHERFORD HEAVY OIL PROJECT ..................................... 43

WEATHERFORD HEAVY OIL SYSTEM SCHEMATIC ..................................................................... 43

3.4.HEAVY OIL PROJECT MAIN OPERATIONS ............................................................. 43

SHIPMENT OPERATION............................................................................................................... 45

LAB TESTING OPERATION .......................................................................................................... 46

QUESTIONS & ANSWERS ...................................................................................................... 47


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List of Abbreviations

Abbreviation Stands For:

API American Petroleum Institute indicates the measure of oil weight (API

gravity)

OPEC Organization of Petroleum Exporting Countries

HC Hydrocarbons

WHP Well head pressure

WHT Well head temperature

BHP Bottom Hole Pressure

BHT Bottom Hole Temperature

CT Casing temperature

CP Casing pressure

bbl Barrel

bpd Barrels per day

Psig Pounds per square inch gauge

Psia Pounds per square inch absolute

SCFD Standard cubic feet per day

BS&W Basic Sediments and Water

TDS Total Dissolved Solids

WC Water cut

SC Sand cut

GOR Gas Oil Ratio

GLR Gas Liquid Ratio

OWC Oil Water contact

GOC Gas Oil Contact

ESD Emergency Shut-down

BOP Blowout Preventer

SRP Sucker rod pump

PCP Progressive cavity pump

ESP Electric Submersible Pump

SPM Strokes Per Minute (of a positive-displacement pump)

SCBA Self Contained Breathing Apparatus

SABA Supplied Air Breathing Apparatus


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PLV Permissible limit value (H2S)

UEL Upper Explosion level (H2S)

LEL Lower Explosion level (H2S)

BO Barrel Oil

BW Barrel WaterBOPD Barrel Oil per day

BWPD Barrel Water per day

LNG Liquefied Natural Gas

LPR Liquefied Petroleum Gas


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Abstract

This book is an overview on Oil Field Foundation and also emphasizes on the Heavy Oil

production. It is mainly oriented to the beginners in Oil Filed as it shows an overview on most

used systems and operations without going through the deep technical details. Weatherford

Kuwait has recently started a Heavy Oil project. This project comes as a contemporary response

to the world Oil Field changes. There are huge, well-known resources of heavy oil, extra-heavy

oil, and bitumen around the world that havent been extracted yet. Technologies that upgrade

value, drive down costs, and reduce environmental impacts will have the greatest effect on

increasing the production of heavy oil.


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Chapter 1 Foundation of Oil Field

1.1.History

OPEC

Foundation of OPEC

The Organization of the Petroleum Exporting Countries (OPEC) is a permanent,

intergovernmental Organization, created at the Baghdad Conference on September 1014,

1960.

The five Founding Members were:

Iran

Iraq

Kuwait

Saudi Arabia

Venezuela

The five Founding Members were later joined by nine other Members: Qatar (1961);

Indonesia (1962) suspended its membership from January 2009; Libya (1962); United Arab

Emirates (1967); Algeria (1969); Nigeria (1971); Ecuador (1973) suspended its membership

from December 1992-October 2007; Angola (2007) and Gabon (19751994). OPEC had its

headquarters in Geneva, Switzerland, in the first five years of its existence. This was moved to

Vienna, Austria, on September 1, 1965.

OPECs Mission

The mission of OPEC is:

Coordinate and unify the petroleum policies of its members

Ensure the stabilization of oil markets in order to secure an efficient,

economic and regular supply of petroleum to consumers

Ensure a steady income to producers and a fair return on capital for the

investor


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Statistics on the world current crude oil reserves

The shown figure shows OPEC share of world crude oil reserves in 2010.According to

current estimates, more than 80% of the world's proven oil reserves are located in OPEC

Member Countries, with the bulk of OPEC oil reserves in the Middle East, amounting to 65% of

the OPEC total. OPEC Member Countries have made significant additions to their oil reserves in

recent years, for example, by adopting best practices in the industry, realizing intensive

explorations and enhancing recoveries. As a result, OPEC's proven oil reserves currently stand at

well above 1,190 billion barrels.


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1.2. Geology

1.2.1. Rock Characteristics

Porosity

Porosity is the amount of void space in a rock, in

other words, its how much water a material can hold.

Permeability

Permeability is how well water can flow through a material, thats controlled by how

large the pores are, and how well connected they are.

Unit of measuring Permeability:

Permeability is measured in Darcy.

< 1 mD : Poor

1 mD < < 10mD : Fair

10 mD < < 100 mD : Good

100 mD < < 1000 mD : Very Good

Darcys Law

Darcy's law is a simple proportional relationship between the instantaneous

discharge rate through a porous medium, the viscosity of the fluid and the pressure drop

over a given distance.


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1.2.2. Exploration of Hydrocarbons

Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum

geologists and geophysicists for hydrocarbon deposits beneath the Earth's surface, such as oil

and natural gas. Oil and gas exploration are grouped under the science of petroleum geology.

Exploration Methods

Visible surface features such as oil seeps, natural gas seeps provide basic evidence of

hydrocarbon generation. However, most exploration depends on highly sophisticated

technology to detect and determine the extent of these deposits using exploration geophysics.

Areas thought to contain hydrocarbons are initially subjected to a gravity survey, magnetic

survey, and passive seismic or regional seismic reflection surveys to detect large scale features

of the sub-surface geology.

Finally, when a prospect has been identified and evaluated and passes the oil company's

selection criteria, an exploration well is drilled in an attempt to conclusively determine the

presence or absence of oil or gas.

Exploration Risk

Oil exploration is an expensive, high-risk operation. Offshore and remote area

exploration is generally only undertaken by very large corporations or national governments.

Typical shallow shelf oil wells cost USD$10 30 million, while deep water wells can cost up to

USD$100 million plus. These factors require the efficiency of the exploration results to be very

high to minimize the total cost and risk.

ExplorationMethods

Surface Data

Magnetic, Gravity,Electromagnetic surveys

Seismic Survey (sunar)2D,3D,4D


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1.3. Reservoirs

Definition

A porous and permeable underground formation containing an individual and separatenatural accumulation of producible hydrocarbons (oil and/or gas) which is confined by

impermeable rock or water barriers.

Most reservoir rocks are limestones, dolomites, sandstones, or a combination of these.

An oil reservoir generally contains three fluids gas, oil, and water with oil the dominant

product. In the typical oil reservoir, these fluids occur in different phases because of the

variance in their gravities. Gas, the lightest, occupies the upper part of the reservoir rocks;

water, the lower part; and oil, the intermediate section.

Oil Traps

Oil traps are usually formed as a result of sudden rock movements which causes spaces

where oil is trapped. The next figure shows the different types of traps.


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Drive mechanisms

A virgin reservoir may be under sufficient pressure to push hydrocarbons to surface. As

the fluids are produced, the pressure will often decline, and production will decrease. Some

techniques can be used in this case to maintain the pressure as will be shown in the next section

of Enhanced Oil Recovery techniques. Artificial drive methods may be necessary too.

Gas cap drive

In reservoirs already having a gas cap (the virgin pressure is already below bubble

point), the gas cap expands with the depletion of the reservoir, pushing down on the liquid

sections applying extra pressure.

Aquifer (water) drive

Below the hydrocarbons may be a ground water aquifer. Water is compressible to a

small degree. As the hydrocarbons are depleted, the reduction in pressure in the reservoir

causes the water to expand slightly which will push up on the hydrocarbons, maintaining

pressure till a certain limit when the water pressure is less than the pressure needed to

push the oil column to the surface.


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1.4. Overview on Drilling Rigs

Definition

A drilling rig is a machine which creates holes (usually called boreholes) or shafts in theground. Drilling rigs are massive structures housing equipment used to drill water wells, oil

wells, or natural gas extraction wells.

They sample sub-surface mineral deposits, test rock, soil and groundwater physical

properties, and also can be used to install sub-surface fabrications, such as underground

utilities, instrumentation, tunnels or wells. Drilling rigs can be mobile equipment mounted on

trucks, tracks or trailers, or more permanent land or marine-based structures.

Major components of the rig include the mud tanks, the mud pumps, the derrick or mast,

the drawworks, the rotary table or topdrive, the drillstring, the power generation equipment

and auxiliary equipment.

Types of Rigs

Rigs are classified into Offshore and Onshore rigs as will be shown through the next

classification

Offshore-based drilling rigs:

1. Jack-up platform

Jack-up platforms (or jack-ups) are

platforms that can be jacked up above the sea

using legs that are lowered, much like jacks. They

usually have 3 or 5 legs. These platforms are

typically used in water depths up to 400 feet (120

m), although some designs can go to 550 ft (170

m) depth.

They are designed to move from place to

place, and then anchor themselves by deployingthe legs to the ocean bottom using a rack and

pinion gear system on each leg.


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2. SemiSubmersible PlatformThese platforms have hulls (columns and

pontoons) to allow the structure to float, but of weight

sufficient to keep the structure upright. Semi-

submersible platforms can be moved from place to

place.

They are anchored but their structure does not

touch the sea bed. Semi-submersibles can be used in

water depths from 200 to 10,000 feet (60 to 3,000

m).They are sometimes referred to as a floater.

3. Drillship

A drillship is a vessel that has been fitted with apparatus for drilling. They are often used

for exploratory drilling of new oil or gas wells in deep water but can also be used for scientific

drilling (mud sampling or techtonic plate

surveys).

Most drillships are fitted with a

dynamic positioning system to maintain

position over the well. They can drill in

water depths up to 12,000 ft (3,700 m).

4. Fixed Platform

A fixed platform is a type of offshore platform used

for the production of oil or gas. These platforms are built on

concrete and/or steel legs anchored directly onto the

seabed, supporting a deck with space for drilling rigs,

production facilities and crew quarters. Such platforms are

designed for very long term use


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Onshore-based drilling rigs:

1. Drilling Rig

Land-based drilling rigs generally consist of engines, a

drawworks, a mast (or derrick), pumps to circulate the

drilling fluid (mud) under various pressures, blowout

preventers, drill string and related equipment. Rock cuttings

are carried to the surface by the circulating drilling fluid.

The intended well depth, bore hole diameter and

drilling site conditions are the principal factors that

determine the size and type of rig most suitable for a

particular drilling job.

2. Workover Rig

Land-based workover rigs (commonly referred to as well servicing rigs) consist of a

mobile carrier, engine, drawworks and a mast. The primary function of a workover rig is to act as

a hoist so that pipe, sucker rods and down-hole equipment can be run into and out of a well.

Land-based workover rigs are easier to

move between well sites and different

geographical areas of operations than

drilling rigs.

Typically, the rigs are self-

propelled and have less auxiliary

equipment to move. Because of size and

cost considerations, workover rigs are

used for these operations rather than

the larger drilling rigs.


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Rig Personnel

All rigs operate on a 24 hours round the clock operation divided into two twelve hour

shifts with a full crew on each. The drill crew on an offshore rig typically consists of an:

OIM (offshore installation manager): Is the senior person in charge of the offshore

platform has both marine and oilfield experience.

Company Man (representative of the oil company): Is the production companys

senior representative on site.

Tool/Tour Pusher: Is the senior drilling person on site.

Drilling Engineer: Is a drilling technical specialist.

Medic: The person who looks after injured personnel on site.

Driller: (may also be called Toolpusher) may report to Toolpusher.

Assistant Driller: Reports to the Driller or Toolpusher.

Derrick Man: Works up high on the derrick, handles the top end of the drill pipe

sections and fluid circulation Equipment. He works on the Monkey Board.

Rig Electrician: Responsible for connecting and maintaining electrical equipment on

the rig site.

Material Coordinator: Ensure adequate and safe supplies of equipment and goods are

brought to site.


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Rig Components

This article lists the main components of a petroleum onshore drilling rig. Offshore

drilling rigs have similar elements, but are configured with a number of different drilling systems

to suit drilling in the marine environment.

It can be mainly divided into 3 categories:

Hoisting System

Rotating System

Circulating System

Hoisting System main components:

Derrick

Travelling Block, Crown Block & Drill Line

Drawworks

Rotating System main components:

Top Drives

Power Swivels

Swivels

Rotaries and Drives

Circulating System main components:

Surface piping & Standpipe

The kelly (rotary) hose The drillpipe & drill collars

The bell nipple

The flowline

The mud-cleaning equipment & mud tanks

The centrifugal pumps


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Drilling Rig Schematic

The shown figure shows an overview on the three previously mentioned systems in

details and the function of each of its components:

1. Mud tank: is often called mud pits and

stores drilling fluid until it is required down

the wellbore.

2. Shale shakers: separates drill cuttings from

the drilling fluid before it is pumped back

down the wellbore.

3. Suction line (mud pump): is an intake line

for the mud pump to draw drilling fluid from

the mud tanks.

4. Mud pump: is a reciprocal type of pump

used to circulate drilling fluid through the

system.

5. Motor or power source

6. Vibrating hose: is a flexible, high pressure

hose (similar to the Kelly hose) thatconnects the mud pump to the stand pipe.

7. Draw-works: is the mechanical section that

contains the spool, whose main function is

to reel in/out the drill line to raise/lower the

traveling block.

8. Standpipe: is thick metal tubing, situated

vertically along the derrick that facilitates the flow of drilling fluid and has attached to it

and supports one end of the Kelly hose.

9. Kelly hose: is a flexible, high pressure hose that connects the standpipe to the Kelly.

10.Goose-neck: is a thick metal elbow connected to the swivel and standpipe that supports

the weight of and provides a downward angle for the Kelly hose to hang from.


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11.Traveling block: is the moving end of the block and tackle. Together, they give a

significant mechanical advantage for lifting.

12.Drill line: is thick, stranded metal cable threaded through the two blocks (traveling and

crown) to raise and lower the drill string.

13.Crown block: is the stationary end of the block and tackle.

14.Derrick: is the support structure for the equipment used to lower and raise the drill

string into and out of the wellbore.

15.Monkey board: is the structure used to support the top end of the stands of drill pipe

vertically situated in the derrick.

16.Stand (of drill pipe): is a section of 2 or 3 joints of drill pipe connected together and

stood upright in the derrick. When they are pulled out of the hole, instead of laying

down each joint of drill pipe, 2 or 3 joints are left connected together and stood in thederrick to save time.

17.Pipe rack (floor): is a part of the drill floor (#21) where the stands of drill pipe are stood

upright. It is typically made of a metal frame structure with large wooden beams

situated within it. The wood helps to protect the end of the drill pipe.

18.Swivel (On newer rigs this may be replaced by a top drive): is the top end of the kelly

that allows the rotation of the drill string without twisting the block.

19.Kelly drive: is a square, hexagonal or octagonal shaped tubing that is inserted through

and is an integral part of the rotary table that moves freely vertically while the rotary

table turns it.

20.Rotary table: rotates, along with its constituent parts, the kelly and kelly bushing, the

drill string and the attached tools and bit.

21.Drill floor: is the area on the rig where the tools are located to make the connections of

the drill pipe, bottom hole assembly, tools and bit. It is considered the main area where

work is performed.

22.Bell nipple: is a section of large diameter pipe fitted to the top of the blowout

preventers that the flow line attaches to via a side outlet, to allow the drilling mud to

flow back to the mud tanks.


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23.Blowout preventer (BOP) Annular type: are devices installed at the wellhead to prevent

fluids and gases from unintentionally escaping from the wellbore. #23 is the annular

(often referred to as Hydril named after a manufacturer), and #24 is the pipe rams and

blind rams.

24.Blowout preventer (BOP) Pipe ram & blind ram

25.Drill string: is an assembled collection of drill pipe, heavy weight drill pipe, drill collars

and any of a whole assortment of tools, connected together and run into the wellbore

to facilitate the drilling of a well. The collection is referred to singularly as the drill string.

26.Drill bit: is a device attached to the end of the drill string that breaks apart the rock

being drilled. It contains jets through which the drilling fluid exits.

27.Casing head or Wellhead: is a large metal flange welded or screwed onto the top of the

conductor pipe and is used to bolt the surface equipment such as the blowoutpreventers (for well drilling) or the Christmas tree (oil well) (for well production).

28.Flow line: is large diameter pipe that is attached to the bell nipple and extends to the

shale shakers to facilitate the flow of drilling fluid back to the mud tanks.

Additional equipment on the rig:

Drilling fluids

Cool & lubricate drilling bit

Control corrosion

Remove cutting from the well

Facilitate cementing and completion

Minimize reservoir damage

Elevators

Used to hold and pull drill pipe or casing

Reamers

Installed above drill bit to enlarge hole size


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1.5. Well Completion

This is considered as one of the most important stages after the drilling process as once a

well is drilled and has been confirmed that commercial quantities are present for extraction; the

well is completed.

Well Completion steps:

Installing the well Casing and Cementing

Completing the well

Installing the well head

Installing the lifting equipment

1.5.1. Casing

Definition

It is the process of lining the hole with steel pipes once it is drilled.The well designer

must design casing to withstand a variety of forces, such as collapse, burst, and tensile failure, as

well as chemically aggressive brines.

The operation during which the casing is put into the wellbore is commonly called

"running pipe." Casing is usually manufactured from plain carbon steel that is heat-treated tovarying strengths, but may be specially fabricated of stainless steel, aluminum, titanium,

fiberglass and other materials.

Function of Casing

The main objectives of casing are:

Prevents the collapse of the borehole

Prevents fracturing of the upper zones and so additional pressure occurs

Facilitates attaching surface equipments (Production tree, Lifting

systems,.)

Restricts production to the well

Provides a well of known diameter for future operations


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Types of Casing

The number of casing layers we use depends on the unique characteristics of the

subsurface and can vary from well to well. Depending on a wells design, well construction can

have between two and four main components. These components include conductor, surface,

intermediate and production casings.

Conductor Casing

Conductor casing is typically the first (and largest diameter) pipe installed during

construction and usually extends between 25 and 45 meters (approximately 80 to 150 feet)

below surface. Conductor casing is inserted into the surface hole and cemented in place along

its full length to ground surface.

Its two primary purposes are:

Holding back any unconsolidated surface sediments

Isolation of shallow groundwater from the contents of the hole

Surface Casing

After the conductor casing is installed and cemented, the hole is drilled deeper and

surface casing is installed and cemented in place. Surface casing can be set anywhere up to 600

meters (approximately 2,000 feet) or more. It is also cemented all the way from the bottom of

the hole to ground surface.

Its two primary purposes are:

Well control

Completely isolating the well

from groundwater aquifers as

surface casing is installed with

the deepest local

groundwater aquifers in mind

and regulated accordingly


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Intermediate Casing

After the surface casing has been set and properly cemented, drilling of the intermediate

hole and installation of intermediate casing begins. In some cases, depending on the unique

characteristics of the subsurface, intermediate casing may not be needed.

Its primary purpose is:

Isolation of any abnormally-pressured subsurface rock formations from

causing instability

Production Casing

Production casing is the final length of steel pipe used in wellbore construction.Production casing typically runs the entire depth of the well and may be cemented in place all

the way to ground surface.

Its primary purpose is:

Isolation of the zone containing natural gas from other subsurface

formations

Pumping hydraulic fracturing fluids into the producing formation without

contacting other formations along the wellbore


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Chapter 2 Artificial Lift

2.1. Artificial Lift Systems

Definition

Any system that adds energy to the fluid in the well having an objective of improving

production of the wells with low reservoir pressure

Purpose of ALS

At first, reservoirs are always at elevated pressure because of underground forces. The

next diagram shows briefly the different types of the reservoirs which was discussed in details in

the reservoirs section as this is an important factor in the choice of the applied artificial lift

system.

Driving forces in reservoirs

Water Drive Reservoir Gas Drive Reservoir

In this case, the reservoir In this case, the reservoir

is connected to a water aquifer obtains its energy either from

that provides the driving gas cap or gas breaking out

mechanism of solution

Through time the reservoirs pressure differential becomes insufficient for the oil to flow

naturally upwards, As a result Artificial Lift systems are used to pump the oil to the surface to

facilitate the production operation.

One of the reasons of why this occurs is that by time when the oil in the reservoir

decreases the percentage of water coming out increases which is heavier than oil and so

increases the pressure formed by the water/oil column till it exceeds the reservoir pressure.

These calculations vary according to the depth of the reservoir and density of the fluid.


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2.2. Oil-Well Behavior

Overview on most Wells Behavior

Most wells produce in a predictable manner called Decline Curve, as production

increases at the beginning for a short period till it reaches its peak at a certain time and then it

starts to decline slowly for a long time.

The time each well takes to decline till it stops production differs from one well to

another as we can find some wells that produce for more than 100 years while others produce

for just few years.

Decline Curve

Oil well production curves typically end in an exponential decline. At natural rates, oilwell production curves appear similar to a bell curve, a phenomenon known as the Hubbert

curve. The typical decline is a rapid drop in production, and eventually a leveling off to a point at

which they no longer produce profitable amounts.

The next figure shows a typical Decline Curve of a given well:

Analysis of Decline Curve

Decline curve analysis is a graphical procedure used for analyzing declining production

rates and forecasting future performance. A curve fit of past production performance is doneusing certain standard curves. This curve fit is then extrapolated to predict potential future

performance.

Decline curve analysis is a basic tool for estimating recoverable reserves. Conventional

or basic decline curve analysis can be used only when the production history is long enough that

a trend can be identified.


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2.3. Enhanced Oil Recovery

Definition

Enhanced Oil Recovery (EOR) is a generic term for techniques for increasing the amountof crude oil that can be extracted from an oil field. Using EOR, 30-60 %, or more, of the

reservoir's original oil can be extracted compared with 20-40% using primary and secondary

recovery.

Classifications of EOR Techniques

Enhanced oil recovery is achieved by gas injection, chemical injection, microbial injection,

or thermal recovery (which includes cyclic or continuous steam, steam flooding)

1. Gas Injection

Gas reinjection is presently the most-commonly used approach to enhanced

recovery. In addition to the beneficial effect of the pressure, this method sometimes aids

recovery by reducing the viscosity of the crude oil as the gas mixes with it.

Gases used include CO2, natural gas or nitrogen.

2. Chemical injection

The injection of various chemicals, usually as dilute solutions, has been used to

improve oil recovery.

Injection of alkaline or caustic solutions into reservoirs with oil that has organic

acids naturally occurring in the oil will result in the production of soap that may lower the

interfacial tension enough to increase production. Injection of a dilute solution of a water

soluble polymer to increase the viscosity of the injected water can increase the amount of

oil recovered in some formations.

3. Thermal methods

In this approach, various methods are used to heat the crude oil in the formation to

reduce its viscosity and/or vaporize part of the oil. Methods include cyclic steam injection,steam drive and in situ combustion. These methods improve the sweep efficiency and the

displacement efficiency.

These methods will be discussed in details in the Heavy Oil section.


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2.4. Types of Artificial Lift Systems

The figure below shows the different types of Artificial Lift systems and the book will go

through each of them in details through the next section.

Artificial LiftTypes

Pump Types

Rod Pumps

Progressive CavityPump (PCP)

ElectricSubmersible Pump

(ESP)

SubsurfaceHydraulic pump

Gas Method Gas Lift


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Mechanism of Operation

The surface operation is mainly transferring energy for pumping the well from prime-

mover to sucker rod string. In doing this, it must change the rotary motion of prime-mover to

reciprocating motion of sucker rod. And it must reduce the speed of prime-mover to suitablepumping speed.

This type of lifting uses a positive displacement pump that is installed in the tubing near

the bottom of the well and this pump goes through a cycle to attain the lifting of the fluid to the

surface.

The pumping cycle starts with the lifting of the traveling valve (TV) at the bottom of the

stroke, the TV is closed and the standing valve (SV) is opened. This lifts the fluid above the TV

and allows fluid to enter the pump through the SV. At the top of the stroke when the TV starts

down and is opened and the SV is closed. The fluid that is now in the pump is trapped there by

the closing of the S V and TV moves under the fluid by being open. The TV and SV are ball and

seat type valves that are in cages to restrict the movement of the ball.


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Mechanism of operation

Downhole pump is mainly formed of a rotor than rotates inside a stator which is

attached to the production tubing.

As the rotor starts rotating, a series of sealed cavities are formed and moves on from the

inlet till the discharge end of the pump which results in a positive displacement flow.

Factors that affects the production rate:

Size of the cavities

Rotational speed of the rotor

Differential pressure across the pump

Analysis of PCP system

As any system the PCP has strong points and weak points. These points are always the

key for the choice of the appropriate Artificial Lift System that can be used in different

reservoirs. The next points show some of the advantages and disadvantages of the PCP system.

Advantages of PCP:

Quiet operation

High system efficiency

Portable, lightweight surface equipment

Simple installation with minimal maintenance costs

Pumps oils and waters with solids

No internal valves to clog or gas lock

Disadvantages of PCP:

Limited lift capabilities at high depths


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Mechanism of operation

At first, the fluid flows into the perforations into the system. This fluid passes past the

motor to aid its cooling process. Afterwards, the flow enters through the intake and passes

through the gas separator till it reach the centrifugal unit.

The centrifugal unit consists of multi-stage rotating impellers which have a function of

adding pressure to the fluid column and builds up pressure till the fluid reaches the surface of

the well.

Analysis of ESP System

As any system the ESP has strong points and weak points. These points are always the

key for the choice of the appropriate Artificial Lift System that can be used in different

reservoirs. The next points show some of the advantages and disadvantages of the ESP system.

Advantages of ESP:

High efficiency at high production rates

Can be applied to deviated wells

Minimum surface equipment requirements

High volume and depth capacity

Disadvantages of ESP:

Poor ability to pump sand

High cost in case of downhole equipment maintenance


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In the operation of a hydraulic lift system, crude oil or water (power fluid) is taken from

a storage tank and fed to the surface pump. The power fluid, now under pressure built up by the

surface pump, is controlled by valves at a control station and distributed to one or more

wellheads. The power fluid passes through the wellhead valve and is directed to the downhole

pump.

In a piston pump, power fluid actuates the engine, which in turn drives the pump,

and power fluid returns to the surface with the produced oil, is separated, and is piped to the

storage tank.

A jet pump has no moving parts and employs the Venturi principle to use fluid under

pressure to bring oil to the surface.

Analysis of Hydraulic Pump System

As any system the Hydraulic Pump System has strong points and weak points. These

points are always the key for the choice of the appropriate Artificial Lift System that can be used

in different reservoirs. The next points show some of the advantages and disadvantages of the

system.

Advantages of Hydraulic Pump System:

Jet Lift

No moving parts

High volume capability

"Free" pump

Multiwell production from a single package

Low pump maintenance

Piston Lift

"Free" or wireline retrievable

Positive displacement-strong drawdown

Double-acting high-volumetric efficiency

Good depth/volume capability (+15,000 ft.)


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Disadvantages of Hydraulic Pump System:

High initial capital cost

Complex to operate

Only economical where there are a number of wells together on

a pad.

If there is a problem with the surface system or prime mover,

all wells are off production.


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2.4.5. Gas lift

Components of Gas Lift System

This system consists mainly of two main parts. The first part is the surface equipments

while the second part is the downhole equipments. The whole system is illustrated in the nextfigure that shows the various components of the system.

The surface equipments consist of:

A gas source

A surface injection system including piping, compressors and needed valves

A surface processing system

The downhole equipments consist of:

A downhole gas lift equipments as mandrels and valves


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In a typical gas lift system, compressed gas is injected through gas lift mandrels and

valves into the production string. The injected gas lowers the hydrostatic pressure in the

production string to reestablish the required pressure differential between the reservoir and

wellbore, thus causing the formation fluids to flow to the surface.

Essentially, the liquids are lightened by the gas which allows the reservoir pressure to

force the fluids to surface.

Gas may be injected continuously or intermittently, depending on the characteristics of

the well and the arrangement of the gas-lift equipment.

Analysis of Gas Lift System

As any system the Gas Lift system has strong points and weak points. These points are

always the key for the choice of the appropriate Artificial Lift System that can be used in

different reservoirs. The next points show some of the advantages and disadvantages of the

system.

Advantages of Gas Lift:

Has few moving parts

Controls production rates from surface

Handles sandy conditions well

Works for both horizontal and deviated producing wells

Disadvantages of Gas Lift:

Not feasible if no source of gas present

High initial capital purchase cost

Maintenance intensive


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The next table compares between the previously mentioned Artificial Lift Systems and

shows when each of them is applicable on the desired well:

OperatingParameters

Rod pump PCPHydraulic

PistonESP

HydraulicJ et

Gas lift

TypicalOperating Depth

100 to 11000ft

2000 to4500 ft

7500 to 10000 ft 12000 ft5000 to10000 ft

5000 to10000 ft

MaximumOperating Depth

16000 ft 6000 ft 17000 ft 15000 ft 15000 ft 15000 ft

TypicalOperating

volume

5 to 1500BFPD

5 to 2200BFPD

50 500 BFPD100 to 30000

BFPD300 - 4000

BFPD

100 -10000BFPD

MaximumOperatingVolume

6000 BFPD 4500 BFPD 4000 BFPD 40000 BFPD>15000BFPD

30000BFPD

TypicalOperatingTemperature

100 - 350 F[40-177 C]

75 - 150 F[24-65 C]

100 - 250 F[40-120 C]

150 - 280 F[65-138 C]

100 - 250 F[40-120 C]

100 - 250

F[40-120

C]

Typical WellboreDeviation

0 - 20 deglanded pump

N/A0 - 20 deg

landed pump0 - 20 deg

landed pump0 - 20 deghole angle

0 - 50deg

MaximumWellboreDeviation

0 - 90 deglanded pump

0 - 90 deg< 15

deg/100 ft

0 - 90 deg< 15 deg/100 ft

0 - 90 deg0 - 90 deg

< 24deg/100 ft

70 deg,short tomediumradius

Corrosionhandling

Good toExcellent

Fair Good Good ExcellentGood toexcellent

Gas handling Fair to good Good Fair Fair Good Excellent

Solids handling Fair to good Excellent Poor Fair Good Good

Fluid gravity > 8 API < 35 API > 8 API > 10 API > 8 API> 15 API

ServicingWorkover or

pulling rigWorkover or

pulling rigHydraulic or

wirelineWorkover or

pulling rigHydraulic or

wireline

Wirelineor

workoverrig

Prime mover Gas orelectric

Gas orelectric

Multi-cylinder orelectric

Electricmotor

Multi-cylinder or

electric

Compressor

Offshoreapplications

Limited Good Good Excellent Excellent Excellent

Systemefficiency

45% - 60% 40% - 70% 45% - 55% 35% - 60% 10% - 30%10% -30%


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Chapter 3 Heavy Oil Project

3.1. Overview on Heavy Oil

Definition

Heavy oil, extra-heavy oil, and bitumen are unconventional oil resources that are

characterized by high viscosities (i.e. resistance to flow) and high densities compared to

conventional oil.

Generally, there is no exploration phase for heavy oil projects in the conventional sense.

The main challenge in heavy oil is not in finding resources, but in the ability for an oil company

to extract, recover, produce, and sell heavy crudes.

Classification of Oil Types

In comparison with heavy oil, light or conventional oil flows naturally and can be pumped

without being heated or diluted. Light oil is characterized by an API gravity of at least 22, and

extra-heavy oil has an API gravity of less than 10.

Light oil

Also known as "conventional oil," light oil has an API gravity of at least 22 and a

viscosity less than 100 centipoises (cp).

Heavy Oil

Asphaltic, dense (low API gravity), and viscous oil that is

chemically characterized by its content of asphaltenes (very

large molecules incorporating most of the sulfur and perhaps

90% of the metals in the oil). Although variously defined, the

upper limit for heavy oils has been set at 22API gravity and a

viscosity of less than 100 cP.

Extra Heavy Oil

It is the heavy oil having an API gravity of less than 10.


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3.2. Heavy Oil Production

Heavy oil Production Techniques

The next diagram shows the classification of production techniques of Heavy Oil. Each ofthese systems will be discussed in details through the next section.

Heavy OilProduction

Systems

ThermalRecovery

Cyclic SteamSimulation

CHOPS

SAGD

Emerging

Vapor Extraction

VAPEX

THAI


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Thermal Recovery Techniques

Thermal methods typically involve the injection of steam or hot water into the reservoir

to improve the mobility of the heavy oil and provide a displacement mechanism. Thermal

methods provide some of the highest recovery factors, but they also have the largest potentialcapital expenditure and operating costs.

1.Cyclic Steam Simulation (Huff & Puff)

Cyclic steam stimulation is a thermal recovery method, is a three-stage process involving

several weeks of steam injection, followed by several weeks of "soaking," followed by a

production phase where the oil is produced by the same wells in which the steam was injected.

As production declines, the injection phase is restarted.

Function of Steam Simulation

Makes the oil more mobile by reducing its viscosity

Creates cracks and channels through which the oil can flow to the wellbore


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2. CHOPS

Cold heavy oil production with sand (CHOPS) is a technique for extracting difficult heavy

crude oil where sand is used as a means enhancing the productivity of the oil well.

Thats because Canadian oil companies discovered that if the sand filters are removedfrom the wells, and as much sand as possible is produced with the oil, the production rates

improved considerably.

3.SAGD

It is a technique that involves the drilling of two horizontal wells, one at the bottom of

the formation and another about 5 meters above it. The upper well injects steam into the

reservoir. The resulting heat melts the bitumen which allows gravity to assist it to flow to the

lower well, and the bitumen is pumped to the surface.

SAGD is cheaper than Cyclic Steam Simulation, allows very high oil production rates, and

recovers up to 60% of the oil.


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Emerging Techniques

It is a second classification of the techniques used in oil recovery and this section will

emphasize on two types of them.

1.VAPEX

It is similar to SAGD, but instead of steam, hydrocarbon solvents are injected into the

upper well to dilute the bitumen and allow it to flow. It is much more energy efficient than

steam injection and some partial upgrading of the bitumen to crude oil occurs right in the sands.

This method is new and more expensive than the above but oil companies are experimenting

with it.

2.THAI

It is a new and experimental method where a vertical air injection well is combined with

a horizontal production well. To begin the process, bitumen around the toe of the horizontal

well is heated with steam. Once this approximately three-month heating cycle in a bitumen

reservoir is complete, the steam is shut off and air is injected into the vertical well to create a

combustion reaction in the reservoir.


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3.3. Overview on Weatherford Heavy Oil Project

Weatherford Heavy Oil System Schematic

The next figure shows the design of Weatherford system that is used in the heavy oil

project. The next section will discuss in details each component of the system and the

mechanism of the system.


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Lab Testing Operation

Oil Sample Test

It is a test done to the oil sample whether it is taken from the extracted oil (wellhead

sample) or from the holding tank (shipped sample). This test is done using the centrifuger device

to show the percentage of each of the oil and water and solids in the sample.

Water Sample Tests

Salinity Test

It is performed using the Refractometer to show the percentage of NACL in thetested water sample.

TDS (total dissolved solids) Test

It is performed using the TDS meter to show the percentage of the rest of solids in

the sample.

PH Test

The pH test measures the H+ ion concentration in liquids and substances. Allmeasured liquids or substances are given a pH value on a scale that a range from 0 to

14.This makes it neutral, acidic or basic.


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Questions & Answers

Q1: What is the porosity and permeability?

Porosity: it is the amount of void space in a rock, in other words, its how much water a

material can hold.

Permeability: it is how well water can flow through a material, thats controlled by how

large the pores are, and how well connected they are.

Q2: Define Viscosity.

It is a measure of the resistance of flow due to internal friction when one layer of fluid is caused to

move in relationship to another layer.

Q3: What is the unit of permeability?

Permeability is measured in Darcy.

< 1 mD : Poor

1 mD < < 10mD : Fair

10 mD < < 100 mD : Good

100 mD < < 1000 mD : Very Good

Q4: How to measure the salinity?

Salinity is measured using a Refractometer.

Q5: State Darcys law.

Q6: When do we use SRP, PCP?

It mainly depends on three factors which are reservoir, hole and operation considerations and

nature as shown in section (2.4, 2.5) in details

Q7: What is the function of the Steam Injection?

Improving the amount of oil recovered by heating the oil to higher temperatures to decrease its

viscosity so that it more easily flows through the formation toward the producing wells.


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Q24: What is the meaning of Oil Saturation and Dead oil?

Dead oil is oil at sufficiently low pressure that it contains no dissolved gas or a relatively thick oil or

residue that has lost its volatile components.

Oil Saturation is expressed as the fraction, or percent of the total pore volume occupied by the oil

Q25: List three methods for oil recovery.

CHOPS, SAGD, Cyclic Steam Simulation and VAPEX

Hatem Naga Training Book - Heavy Oil

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Transcript of Hatem Naga Training Book - Heavy Oil