Report It

REPORT ON STUDENTS’ INDUSTRIAL WORK EXPERIENCE

SCHEME (SIWES) TRAINING PROGRAMME

(APRIL 2012– AUGUST 2012)

AT

ADDAX PETROLEUM DEVELOPMENT (NIG) LIMITED

THE DRILLING DEPARTMENT,

32, Ozumba Mbadiwe street.

Victorial Island, Lagos

BY

RAJI ADEDOLAPO

(07CF05869)

DEPARTMENT OF CHEMICAL ENGINEERING

COVENANT UNIVERSITY

BEING A REPORT SUBMITTED TO THE DEAN, COLLEGE OF SCIENCE AND

TECHNOLOGY IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR GEC 429

DEAN CST: PROF. F. K. HYMORE

SEPTEMBER 2012.

DEDICATION

I dedicate this work to the Almighty GOD, my family & friends, my professors and lecturers

and to the chemical engineering department of Covenant University, Ota.

Adedolapo Raji Page 2

ACKNOWLEDGEMENTS

I wish to express my profound gratitude to the management and staff of Addax Petroleum

Development (Nigeria) Limited, Lagos, for giving me the opportunity to undergo this

intensive industrial training in the organization. I am also grateful to the entire staff of the

drilling department particularly the General Manager, Mr Horace Awi.

My special thanks to the OML 126/137 team, Mr Tayo Ajimoko for taking me under his

wing. Roy Hofsoy, Eleanor Okubor, Gbenga Aderobaki, Ugo Okoli, Chike Nwagu, Tokunbo

Ayodele and Tinuade Edu.

My deep appreciation to Olatunji Ayeni for all his help; Tony Lovering, Sheldon ‘sudds’

Sutherland, Fernando Villegas, Lucy Fajembola, Kehinde Ladejo, Dami Ajayi and John

Ogumike for making this experience splendid. Also a big thanks to the Asset management,

Production and HSE departments for all their help.

To my parents, thank you for all your care and support. Finally, I want to thank the school for

this great opportunity they have assisted in breaching the gap between practical and theory.


ABSTRACT

As the value of non-renewable hydrocarbon reserves and the cost of remedial work increases,

a renewed emphasis is being placed on proper well drilling and completion techniques.

Maximum reliability and productivity is essential. This report outlines the problems that can

arise from poor planning, engineering and execution of cement placement operations and the

importance of effective drilling mud engineering. These objectives are difficult to attain in

unconsolidated sand formations which are always subject to structural failure. This is why the

afore stated mechanisms are exceedingly crucial and is influenced by every completion

operation.


TABLE OF CONTENTS

DEDICATION……………………………………………………………………………….2

ACKNOWLEDGEMENTS…………………………………………………………………3

ABSTRACT………………………………………………………….……………………....4

COMPANY PROFILE ……………………………………………………………………..6

CHAPTER ONE: INTRODUCTION: PARTICIPATION / WORK DONE

1.0 INTRODUCTION: OVERVIEW OF ADDAX’s ASSETS…………………………7

1.1 PARTICIPATION /WORKDONE…………………………………………………...8

1.2 DRILLING OPERATIONS AND PROCEDURES………………………………….9

1.3 SCARABEO 3 RIG…………………………………………………………………..18

CHAPTER 2: EXPERIENCE GAINED

2.1 DRILLING ENGINEERING OPERATIONS FUNDAMENTALS………………….48

2.2 THE FUNDAMENTALS OF HOW THE RIG WORKS………………………………49

2.3 SAFETY AWARENESS……………………………………………………………….52

CHAPTER THREE: CHALLENGES ENCOUNTERED……………………………….53

CHAPTER FOUR: OBSEREVATIONS AND CONTRIBUTIONS …………………..54

CHAPTER FIVE: CONCLUSION …..............................................................................55

CHAPTER SIX: CHALLENGES FACED BY FIRM……………………………………56

REFERENCES……………………………………………………………………………...57


COMPANYS PROFILE

Addax Petroleum Corporation (Addax Petroleum) is an international oil and gas exploration

and production company focused on Africa and the Middle East. Addax has an asset base

consisting of a number of producing properties in Nigeria and Gabon, and exploration and

development properties and opportunities in West Africa and the Kurdistan Region of Iraq.

Addax Petroleum is a subsidiary of the Sinopec Group, one of the largest oil and gas

producers in China, the biggest oil refiner in Asia and the third largest worldwide.

Addax Petroleum's mission is to create value through successful exploration,

development and production of oil and gas resources whilst contributing to the socio-

economic development of its host societies and maintaining environmental

sustainability. The Company aims to grow its business through reinvestment and

strategic acquisitions in Africa, the Middle East and any other areas with proven

potential, supported by long-lasting relationships with all its stakeholders.

Addax Petroleum began operations in Nigeria in 1998 by signing two Production

Sharing Contracts (PSCs) with the Nigerian National Petroleum Corporation (NNPC).

Our average annual production was 8,800 barrels per day (bbl/d). Since this acquisition,

Addax Petroleum has driven its growth by acquiring oil properties deemed by others to

have limited remaining production potential and using its strong in-house technical and

operational expertise to grow reserves and production in a cost effective manner.

In Nigeria, Addax Petroleum’s producing assets include 11 field complexes with around

60 production wells in concession OML123, 2 fields with 20 producing wells in

concession OML 124 and 2 fields with 14 production wells in concession OML126.

Ongoing progress with Field Development Planning is expected to result in a significant

increase in our production, from the present combined 75.000 bbl/d from OML123,

OML124 and OML126 to over 85000 bbl. /d at the end of 2012.


CHAPTER ONE: INTRODUCTION (PARTICIPATION /WORKDONE)

1.0 INTRODUCTION: OVERVIEW OF ADDAX’s ASSETS

Addax Petroleum is an international oil and gas exploration and production company.

Addax currently operates in Nigeria (strictly exploration and production), JDZ, and

Cameroon, Gabon, Middle East, New Ventures, Petroleum reserves and other resources (oil

and gas).

In Nigeria, the company’s asset activities are OML124, OML 123 and OML 126/137.

OML 124

OML 124, Addax Petroleum’s sole onshore property in Nigeria, is located in Imo state

approximately 100 km north of Port Harcourt. OML 124 is Addax Petroleum’s smallest

Nigerian license area when measured by reserves and production. It contains two producing

oil fields, Ossu and Izombe, which are operated as a common production area. It contains

several identified exploration prospects in the central and south east parts of the property

respectively. The production facilities at OML 124 include the following:

Izombe Flow station

Gas compressors

Water injection pumps

Three flow lines from Ossu to the Izombe Flow station.

The rig operating on it was HPEB TNL 187.

OML 123

OML 123 is Addax Petroleum’s largest license area as measured by reserves and

production. It is located offshore approximately 60km south of the town of Calabar in the

south- eastern part of Nigeria. It contains eight producing oil fields (Adanga, Oron West,

North Oron, Ebughu and extensions, Adanga North Horst, Akam, Bogi and Mimbo. Two

undeveloped oil fields are Kita Marine and Antan and four appraised oil discoveries are

Inagha, Adanga East, Adanga West and Ebughu NE-A). The key production facility is a

knock Adoon FPSO which gathers produced crude oil production or well head platforms on

each field.


The rigs in operation in these fields include Adriatic IX, Seawolf Onome and High Island

VII.

OML 126/137

OML 126 and OML137 are two contiguous blocks located 90km offshore, south of Port

Harcourt. They represent Addax Petroleum’s largest Nigerian properties as measured by

area and also account s for the majority of the company’s recent production growth. The

southern half of OML126 has been completely surveyed by 3D seismic and contains two

oil producing oil fields (Okwori and Nda)., three underdeveloped oil discoveries and three

identified exploration prospects. OML 137 was surveyed by 3D seismic and contains

Ofrima North oil discovery and several potentially commercial natural gas discoveries

(Shokoloko, Toriye, Odum, Asanga, Ofrima and Udele West). They key production facility

is an FPSO which as a processing ability.

The rigs in operation include Transocean GSF 135 and Saipem Scarabeo 3 (this was the

team I was a part of).

1.1 PARTICIPATION /WORKDONE

The student industrial work experience scheme (SIWES) has expanded my horizon in oil and

gas engineering aspect of chemical engineering, due to my participation and work done

during the training period. However, during the course of SIWES programme, I was actively

involved in:

Attending daily drilling meetings, monitoring the performance of drilling operations

and accurate reporting of daily rig operations.

Giving a detailed report of the current operations on the rig, and also the forecast as

pertaining to the OML 126/137 rig (Scarabeo 3 rig).

Attend the weekly HSE meeting, turn in STOP (safety training observation program)

cards, and analyse and discuss safety issues and incidents as a team.

Assisted in Preparing monthly drilling project forecast using Microsoft Project and

ensured accurate saving and updating of the electronic daily drilling reports


Clearly reported decisions, recommendations and actions from drilling departmental

meetings. ,

Liaised with specialist contractors and suppliers such as cement companies or

suppliers of drilling fluids as well as coordinated and facilitated service awareness

sessions by service contractors to Addax

Assisted in the preparation of casing tally sheet and cementing calculations.

Provided short term well site drilling engineering support

Performed sample analysis tests with the mud logging crew and was able to describe

samples.

Well Engineering calculations and analysis to support Rig operations daily such as

Torque and Drag, Hydraulics, cement volume and displacement calculations, mud

volume calculations, Casing/Liner tallies and space-outs.

Facilitation and presentation of pre-spud Meetings and well drilling progress.

Monitoring and reporting well performance analysis, NPT, time, cost, and non-

conformance to management.

Knowledge management: capturing lessons learnt and incorporating them into Rig

operational procedures and drilling program. Learning about the procedures for

various operations through comprehensive discussion with the engineers, contractors

and drilling meetings.

1.2 DRILLING OPERATIONS AND PROCEDURES

As a result of the daily drilling meeting attended, I was able to better understand the

procedures involved in drilling operations, which include the:

DWOP (drilling well on paper): also known as drilling well optimization process or drilling

well on paper. It is the process showing a detailed well design of the drilling process, and

analysing each step of the process to generate ideas for improving performance and reducing

cost. The DWOP is usually designed by the drilling engineer.

However, it is important to note that the DWOP is an interactive session in which the

procedures and design are open to criticisms, and intelligent solutions are suggested and

considered for smooth operations.


In oil and gas drilling, after the rig has been moved to the location, and all the equipment

have been properly rigged up, the following procedures take place progressively.

Spudding: This involves starting the well drilling process by removing rock, dirt and other

sedimentary material with the drill bit. It is the first step of drilling a new well. It involves

drilling the hole with a large diameter bit, this hole however is referred to as the conductor

hole, usually a few hundred feet. The hole diameter could be (16-20)” inches for onshore

drilling, or (30-42)” for offshore drilling. However the particular hole diameter used when

spudding depends on the drilling program as designed by the drilling engineer.

• Running in hole and cementation of conductor casing

• Running in hole and cementation of surface casing

• Running in hole and cementation of intermediate casing

• Running in hole of production casing or liner

Running in hole and cementation of the conductor casing: This is the next phase after

spudding. In this phase, the conductor casing is run in hole, and it is usually within a few

hundred feet in depth from the surface, to the end of the hole section, and then cemented in

place.

Running in hole and cementation of the surface casing: After the surface hole has been

drilled, the surface casing is run in hole, with a casing hanger attached to the last string of

casing to hold it in place.

Running in hole the intermediate casing: This is usually the longest section in a wellbore.

The intermediate casing is a casing that runs through from the end of the surface casing deep

down, vertically or horizontally.

Running in hole the production casing: This is the last casing that is run into the wellbore,

depending on the type of completion; it is either run to the top of the pay zone, or across the

pay zone.


FIGURE 1.1 SCHEMATIC FROM CONDUCTOR TO PRODUCTION CASING.

1.2.1 CEMENTATION

This is a process that takes place at almost every section of the well. Usually takes place

after the casing has been run to the bottom of the hole. There are various types of cementing

which include:

• Primary cementing- casing and liner cementing

• Secondary cementing-Plug and squeeze cementing

Casing cementing: During cementation, the bottom plug is released ahead of the cement slurry. This bottom plug wipes the mud ahead of the cement slurry to minimize the contamination of the cement with the mud. The desired volume of


cement slurry is then pumped into the casing and a top wiper plug is released by pumping drilling fluid or completion fluid into the casing behind the top plug. When the bottom plug reaches the float collar, the diaphragm in the plug ruptures, allowing the cement slurry to be displaced to the guide shoe.

Liner cementing: Liners are attached to the last casing string and not all the way to

the top, usually with a more complex cementation than that casing

Plug cementing: The major function is to prevent fluid communication between an

abandoned lower portion of the well, and the upper part. When cementing the casing, a bridge

plug is placed below the cement plug to assist in forming a good hydraulic seal. It is usually

used for temporary or complete abandonment.

I had a natural flair for the cementing process and drilling fluids because of its relation to

chemical engineering and its great importance to the entire drilling operation. The most

important functions of a cement sheath between the casing and borehole are:

• To prevent the movement of fluids from one formation to another or from the formations to

surface through the annulus between the casing and borehole.

• To support the casing string (specifically surface casing)

• To protect the casing from corrosive fluids in the formations.

However, the prevention of fluid migration is by far the most important function of the

cement sheath between the casing and borehole.

FIGURE 1.2 DIAGRAM OF TOP AND BOTTOM PLUG.


FIGURE1.3 SCHEMATIC OF CASING CEMENTATION.

1.2.2 DRILLING FLUIDS

Drilling fluid (or drilling mud) is a circulating fluid to perform various functions in drilling

operations. Such functions include:

• Remove cuttings from well as well as maintain wellbore stability.

• Suspend and release cuttings

• Seal permeable formations while controlling formation pressures

• Minimizing formation damage and Ensure adequate formation evaluation.

• Cool, lubricate, and support the bit and drilling assembly

The three main categories of drilling mud are:


• Water-based mud: Here the water is the continuous phase, in which oil is present in

discontinuous droplets. The water used can be fresh water, sea water, brine etc., in

which brine is used in shale formations for shale inhibition.

• Oil-based mud: Here the oil (diesel or synthetic-base oil) is the continuous phase

with a trace amount of water, less than 5% of the mud composition.

Oil-based mud is generally more expensive than water-based mud, due to:

• Good rheological properties at high temperatures

• More inhibitive than WBM

• Effective against all types of corrosion

• Superior lubricating characteristics

• Permits mud densities as low as 7.5ppg.

However, the type of mud used depends on the formation and reservoir characteristics,

but it is crucial to use SOBM/POBM (synthetic/polymer oil-based mud) for high

temperature and pressure zones, due to their:

Increased lubricity

Enhanced shale inhibition

Greater cleaning abilities with less viscosity

Withstand greater heat without breaking down.

Note: Regardless of the mud type used to drill a particular well, it must be properly conditioned in terms of density, pH, viscosity, gel strength etc. before being used to drill a particular well.

Barite is used to increase mud weight, while bentonite is used to increase the viscosity.

1.2.3 COMPLETIONS

Completion is the process of making a well ready for production. This principally involves preparing the bottom of the hole to the required specifications, running in the production tubing and its associated down hole tools as well as perforating and stimulating as required. The types of completion include:


Open-hole completions: A well completion that has no casing or liner set across the pay zone or producing formation, therefore allowing the produced fluids to flow directly into the wellbore. This type of completion suffers the major disadvantage that the sand face is unsupported and may collapse.

Cased hole completion: This involves running casing or a liner down through the production zone, and cementing it in place. Connection between the well bore and the formation is made by perforating. Because perforation intervals can be precisely positioned, this type of completion affords good control of fluid flow, although it relies on the quality of the cement to prevent fluid flow behind the liner. As such it is the most common form of completion.

Tubingless Tubing completion Tubing completion Dual tubing

Completion without packer with annulus packer completion with packers

FIGURE1.4 UPPER COMPLETION METHODS.

1.2.4 TYPES OF OPEN-HOLE COMPLETIONS

Barefoot completions(no tubular across the reservoir phase or pay zone)

Predrilled liner and pre-slotted liner

Open- hole standalone screens

Open-hole gravel packs.

A perforation in the context of oil wells refers to a hole punched in the casing or liner of an

oil well to connect it to the reservoir. In cased hole completions, the well will be drilled down

past the section of the formation desired for production and will have casing or a liner run in

separating the formation from the well bore. The final stage of the completion will involve

running in perforating guns, a string of shaped charges, down to the desired depth and firing

them to perforate the casing or liner. A typical perforating gun can carry many dozens of

charges.


http://en.wikipedia.org/wiki/Completion_(oil_well)

http://en.wikipedia.org/wiki/Oil_reservoir

http://en.wikipedia.org/wiki/Oil_well

http://en.wikipedia.org/wiki/Casing_(oil_well)

http://en.wikipedia.org/wiki/Oil_well

FIGURE1.5 OPEN AND CASED-HOLE COMPLETION.

The disadvantage is that perforating can lead to "skin damage", where debris from the

perforations can hinder productivity of the well. In order to mitigate this, perforating is

commonly done underbalanced (lower pressure in the well bore than in the formation) as the

higher well bore pressure will cause a surge of fluids into the well at the point of perforating,

hopefully carrying the debris with it.


FIGURE 1:7 WIRELINE CONVEYED PERFORATION.

1.2.5 ARTIFICIAL LIFT

After completing a well, sometimes the reservoir pressure might not be high enough for the

well to flow, however various techniques are applied to artificially lift the well. They include:

• Gas lift

• Hydraulic fracturing

• Acidizing

Gas lift: Is one of a number of processes used to artificially lift oil or water from wells where

there is insufficient reservoir pressures to produce the well. The process involves injecting

gas through the tubing-casing annulus. Injected gas aerates the fluid to reduce its density; the

formation pressure is then able to lift the oil column and forces the fluid out of the wellbore.

Gas may be injected continuously or intermittently, depending on the producing

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


FIGURE 1:8: GAS LIFT MANDEREL

1.3 Scarabeo 3 Rig.

Scarabeo 3 rig is a semisubmersible rig, with 3 pontoons on which the rig floats.

A pontoon is a long, relatively narrow, and hollow steel float with a rectangular or round

cross section.

Semisubmersible rigs do not submerge to the point where their pontoons contact the sea

bottom. They are below sea level to maximize rig stability.

The rig has three legs labelled, the white, green and the red leg. The rig has 9 anchors, 3

anchors per leg for stability.


Fig 1.9- TRIP TO SCARABEO 3 RIG

GENERAL DATA

Table 1: Scarabeo General Data

1.3.1 RIG OVERVIEWA drilling rig has many pieces of equipment and most of it is huge. But a rig has only one

purpose: to drill a hole in the ground. Rig is a complex arrangement of mechanical/electrical

equipment used in the oil industry to drill oil wells, lower and cement casing, carry out

logging, well testing and for secondary well intervention (Work overs).

The type of rig selected for any drilling operation is highly important because it determines

the safety, efficiency and cost of the well.


Rigs can be generally classified into Land and Marine rigs

MARINE RIGS

Drilling Rigs used offshore are termed marine rigs. A common grouping system for marine

rigs is based on the bottom support of the rig on the seafloor. A bottom supported rig rests

on the seafloor. Floating rigs rely on ballast systems similar to shipping vessels for support

and do not rest on the seafloor. Rigs that fall into each category are as follows:

BOTTOM SUPPORTED FLOATING

1. Barges

2. Jackups

3. Platform

4. Self- contained

5. Arctic types

6. Submersible

Bottom supported unit

Barges- A drilling barge is used typically in 8-20ft of water. The barge is towed to the

location and sink on the bottom by flooding various vessel compartments. After drilling has

been completed, the flooded compartments are evacuated, which allows the rig to float so it

can be moved to the next location.

Jackups: A Jackup rig is perhaps the most widely used marine vessel for exploratory

drilling. The principal components are barge-type unit and three to five legs capable of

supporting the vessel when extended.The jackup is towed to the location and spotted over or

near the well site, depending on the rig type

Floating unit

Drillships: Floating rigs such as Drillship do not rest on the seafloor during drilling.

Drillships use a ship-type vessel as the primary structure to support the rig. Drill ships are

very mobile because they are self-propelled and have a streamlined hull, much like a regular

ocean-going ship.A drillship is a good choice for drilling remote locations. For one thing, it

can move at reasonable speeds under its own power. Anchors keep some drill ships on station

while drilling.


Semisubmersibles: Most semisubmersible rigs have two or more pontoons on which the rig

floats. A pontoon is a long, relatively narrow, and hollow steel float

with a rectangular or round cross section. Semisubmersibles rig do not submerged to the

point where its pontoon contact the sea bottom e.g. Scarabeo 3

1.3.2 THE SYSTEMS ON A RIG

Making a hole with a rotary rig requires qualified personnel and a lot of equipment.

The systems on the rig can be divided into four:

♦ Power System

♦ Hoisting System

♦Rotating System

♦Circulating System

Power System:

Every rig needs a source of power to run the hoisting, circulating, and, in many cases, the

rotating equipment required to make hole. Powerful diesel engines drive large electric

generators. The generators, in turn, produce electricity that flows through cables to electric

switch and control equipment enclosed in a control cabinet. From the control gear, electricity

goes through more cables to electric motors.

Scarabeo 3 uses the internal combustion engines as a prime power source.8 engines and 8

Generators.7 engines are always in use, but the other one is used in case of emergency. The

engine drives the Generator and the Generator provides electricity to the power plant.

Diesel engines are used because they do not have spark plugs. The bigger the rig, the deeper

it can drill and the more power it needs.

Hoisting System:

A rig’s job is to drill a hole; to do this job it must have a hoisting system. A typical hoisting

system is made up of the drawworks (or hoist), a mast or derrick, the crown block, the

travelling block, and the wire rope drilling line.

♦Drawworks: This is a hoisting mechanism on a drilling rig. It is essentially large winch that

spools off or takes in the drilling line and thus raises or lowers the drillstem and the bit.


Fig 1.10 Drawwworks

♦Blocks and Drilling Line

Drilling line is made from a very strong wire rope. Drilling line is stored on a reel (supply

reel). The line comes off a large reel-from the supply reel; it goes to astrong clamp called the”

deadline anchor. From the deadline anchor, the drilling line runs up to the top of the mast or

derrick to a set of large pulleys. This large set of pulleys is called the crown block.

The drilling line is reeved (threaded) several times between the crown block andanother large set of sheaves called the Travelling block.

♦Masts and Derricks: Masts and derricks are tall structural towers that support the blocks

and drilling tools. They also provide height to allow the driller to raise the drill string so crew

members can break it out and make it up.

Rotating Systems:

Rotating equipment turns the bit. Generally rigs can rotate the bit in one or three ways:

• Rotary table with a turntable

• Master bushing

• Bit

• Downhole motor

• Power drive

• Top drive system

• Drill string


• Rotary Steerable (Power drive)

Fig 1.11 Derrick

Turntable: This produces a turning motion that machinery transfers to the pipe and bit.

Master Bushing: A rotary table master bushing fits inside the turntable. The turntable rotates

the master bushing. The master bushing has an opening through which crew members run

pipe into wellbore.

Top Drive System:

This system does away with the Kelly and thus the Kelly drive bushing—a top drive also

called “Power Swivel” rotates the drill string and bit. The main advantage of a top drive over

a Kelly-and-rotary table system is that a top drive makes it safer and easier for crew

members.


Figure 1.11- A Top drive (TDS)

Downhole Motors:

Downhole motor rotates the bit and not the drill pipe. Drilling mud powers most

downhole motors. Crew members install the motor in the drillstring just above the bit.

To make a mud motor rotate the bit, the driller pumps drilling mud down the drill string as

usual.

.

Figure1.12- Mud motor

Rotary Steerable (Power drive): These are now used to be able to make changes in

inclination and azimuth while the drillstring rotates continuously. They produce a cleaner,

smoother wellbore while reducing drag, improving the transfer of weight to the bit and

increasing the rate of penetration. Powerdrive drills faster and more efficiently than

conventional steerable downhole motors.


Drillstring: Most of the drillstring is made up of drill pipe but crewmembers make up

enough drill collars to put the required weight on the bit. The amount of weight a bit requires

to drill efficiently varies considerably and depends on the type of bit and the type of

formation it is drilling.

Each end of each joint is threaded. One end has inside or female threads; the other has outside

or male threads. The female end is called the “box”, and the male end is called

the “Pin”. The threaded ends of drill pipe is called the “Tool joints”

Bits: A rig’s primary job is to rotate a bit on the bottom of the hole. The bit is the business

end of a drilling rig, because the bit drills, or makes the hole. There are two types of bit: the

Roller cone & Fixed-Head bit.

Figure 1.13a- A roller cone bit has teeth Figure 1.13b-Drill collars put weight on the bit

(Cutters) that roll, or turn, as the bit rotates.

Circulating Systems

One unique characteristic of rotary drilling is the pumping of drilling fluid to the bottom of

the hole to pick up cuttings made by the bit and lifts them to the surface for disposal.

Some formations swell in the presence of water and impede drilling, so the operating

company requires that the contractor use oil instead of water as a base for the mud.

Without circulation, drilling stops.


Drilling Fluids,

- Raises cuttings made by the bit to the surface.

-Cools and lubricates the rotating drill stem and bit.

- Keeps underground pressure in check.

CIRCULATING EQUIPMENT

Circulating equipment includes the mud pump, Discharge Line, Stand pipe, the Rotary hose,

swivel (or top drive), drill pipe, drill collars, bit, annulus, Return line, shale shaker, desilter,

desander, degasser, mud tanks, and sunction line.

The Process:

The mud pump takes mud from the mud tanks and sends it out a discharge line to a

standpipe. Mud flows out of the standpipe and into the rotary hose, which is connected to

the top drive. Mud goes through passageways inside the TDS. Once mud leaves the TDS,

mud flows down the drill stem, out the bit. It does a sharp U-turn and heads back up the hole

in the annulus, the mud carries the cuttings made by the bit.

Finally, the mud leaves the hole through a steel pipe called the mud return line and falls

over a vibrating, screen like device called the shale shaker.

The system circulates the mud over and over throughout the drilling of the well.

From time to time, however, crewmembers may add water, clay or other chemicals to make

up for losses or to adjust the mud’s properties as the hole drills into new and different

formations. Several pieces of auxiliary equipment keep the mud in good shape, these

equipment are:

Shale shakers: Sifts out the normal- sized cuttings. But sometimes, though, the bit creates

particles so small that they fall through the shaker with the mud. After the mud passes

through the shale shaker, the system sends the mud through;

Desanders: Remove fine particles or solids from mud.

Desilters: Remove fine solids from the mud; desilters remove solids that are even smaller

than those the desander removes.

Mud cleaners: Like desanders and desilters, also remove small solid particles from

the mud.

Degasser: This is used to removes small amounts of gas that enter the drilling mud as it

circulates past a formation that contains gas.


FIGURE 1.13 COMPONENTS OF A RIG CIRCULATION SYSTEM

1.3.3 CEMENTING OPERATION ON THE RIG

Generally, in the completion of the oil and gas wells, cement is used to isolate the wellbore,

preventing casing failure and keeping wellbore fluids from contaminating freshwater

aquifers.

In an Oil/gas well, the primary functions of cement are:

Provide optimum zonal isolation

Provide casing support and protection against corrosive fluids

Support the borehole.

Basic Ideas that can help ensure a successful cement job:

• Conditioning the drilling fluid: Modifying the flow properties of the drilling fluid to

optimize its mobility and drill cuttings removal.

• Using spacers and flushes: Spacers and flushes are effective displacement aids because

they separate unlike fluids such as cement and drilling fluid.


• Moving the pipe: Pipe rotation or reciprocation before and during cementing helps break

up gelled, stationary pockets of drilling fluid and loosens cuttings, trapped in the gelled

drilling fluid.

• Centralizing the casing: Centralizing the casing with mechanical centralizers across the

intervals to be isolated helps optimize drilling fluid displacement. In poorly centralized

casing, cement will bypass the drilling fluid by following the path of least resistance; as a

result, the cement travels down the wide side of the annulus leaving drilling in the narrow

side.

• Design cementing job on the basis of actual wellbore circulating temperatures.

Oil well cement is manufactured to API specification and is divided into 8 classes (A-H)

depending upon its properties.

Class G& H are basic well cements which can be used with accelerators and retarders to

cover a wide range of depths and temperatures. Additional chemicals are used to control

slurry density, rheology, and fluid loss, or to provide more specialised slurry properties.

Accelerators: Chemicals, which reduce the thickening time of slurry and increase the rate of

early strength development. E.g. Calcium chloride (CaCl2) Sodium chloride (NaCl) &

Seawater

Retarders: Chemicals, which extend the thickening time of slurry to aid cement placement.

E.g. Calcium lignosulphanate (sometimes with organic acids) or saturated salt solutions

Extenders: These materials are used to reduce slurry density for jobs where the hydrostatic

head of the cement slurry may exceed the fracture strength of certain formations. In reducing

the slurry density the ultimate compressive strength is also reduced and the thickening time

increased. E.g. Bentonite, pozzolan and diatomaceous earth..

Heavyweight additives: Heavyweight additives are used when cementing through over

pressured zones. These materials usually increase slurry density. E.g. Barite (barium

sulphate) hematite (Fe2O3) and sand.


Dispersants: Chemicals, which lower the slurry viscosity and may also, increase free water.

Dispersants are added to improve the flow properties of the slurry. Polymers (0.3 - 0.5 lb/sx

of cement), salt (1 - 16 lb/sx) and calcium lignosulphanate (0.5 - 1.5 lb/sxg).

Fluid-loss additives: Materials, which prevent slurry dehydration and reduce fluid loss to the

formation as well as premature setting. E.g. Carboxymethyl hydroxyethyl cellulose

(CMHEC)

Loss circulation control agents: Materials, which control the loss of, cement slurry to weak

or fractured formations.

Miscellaneous agents include Anti-foam agents, fibres, latex etc.

Casing and Cementing hardware

Guide shoes: A guide shoe is used to guide the casing through the hole, avoiding jamming

the casing in washed out zones, or in deviated wells.

Float collar: Is a one-way valve placed at one or two joints above the shoe. The float collar

provides the same functions as a float shoe by preventing fluid back flow into the casing:

mud backflow during running in hole and cement slurry backflow after cement displacement.

The distance between the shoe and float collars is called Shoe track.

Centralizers: They are used to centralise the casing within the hole to improve the cementing

process.


FIGURE 1.14 SCRATCHERS AND CENTRALIZERS

CEMENTING (Halliburton cementing unit)

Cementing companies stock many kinds of cement and have special equipment to transport it

to the well.

The cement is mix with water to form slurry-a thin, watery mixture that is easy to pump.

Many kinds of mixers are available to blend the water and cement into a uniform mixture as

the cement pumps move it down the casing.

Special high-pressure pumps move the slurry through very strong pipe, or lines, to a

cementing head, or plug container.

Cementing crew mounted the cementing head on the topmost joint of casing hanging in the

derrick. Just before the slurry arrives at the head, a crew member releases a rubber plug, a

bottom plug, from the cementing head. The bottom plug separates the cement slurry from any

drilling fluid inside the casing and prevents the mud from contaminating the cement. The

slurry moves the bottom plug down the casing. The plug stops, or seats, in the float collar.

Continued pumping breaks a membrane on the bottom plug and opens a passage. Slurry then

goes through the bottom plug and continues down the last few joints of casing. It flows

through an opening in the guide shoe and up the annular space between the casing and the

hole. Pumping continues until the slurry fills the annular space. As the last of the cement

slurry enters the casing, a crew member releases a top plug from the cementing head. A

top plug is like a bottom plug except that it has no membrane or passage. The top plug

separates the last of the cement to go into the casing from displacement fluid.

Continued pumping moves the cement, the top plug, and the displacement fluid down the

casing. Most of the cement slurry flows out of the casing and into the annular space.

Soon, the top plug seats on or bumps, the pump operates shuts down the pumps. Cement is

only in the casing below the float collar and in the annular space. Most of the casing

is full of displacement fluid.


FIGURE 1.15 CEMENT SILO

FIGURE 1.16 CEMENT MIXERS FOR ADDITIVES


FIGURE 1.17 CONTROL PANEL


FIGURE 1.18 GUAGE

1.3.4 CEMENT SHEATH PLACEMENT BEHIND THE 9-5/8” CASING

OF THE OKWORI WELLS

The above is a technical report I worked on for the Okwori wells (being drilled by the

Scarabeo 3 rig for OML 126/137). It investigates the operation and review s it to enhance

cement sheath placement for efficient cased hole completions. The entire report is lengthy,

for the sake of this report would review for the Okwori 22 well.

EXECUTIVE SUMMARY

In any successful primary cementing operation, the magnitude of displacement of the drilling

mud by the cement slurry in the annulus is very important else a good bond will not be

achieved. The importance of a good cement bond between the casing and the formation

cannot be over emphasized; it is a critical component of well architecture for ensuring casing

mechanical support, protection from fluid corrosion, and most importantly isolating

permeable zones at different pressure regimes to prevent hydraulic communication.

It became important to perform an investigation about the cementing operations on the OML-

126/137, after cement bond logs for different wells showed that there was bad bonding

especially in the sands. The OK-22, OK-24 HST and OK-25 wells from the OML-126 were

chosen for this study, while the Ofrima-4 was chosen from the OML-137 so as to investigate

if the petro-physical properties of the sands (porosity, permeability, wettability) had an


influence on the placement of the cement in the annulus, but cement placement was also

observed in the sandy region of this well, this thus narrowed this study towards the cement

placement practices. The Baker Atlas Segmented Bond Tool (SBT) was used for the

evaluation of the cement placement in these wells.

This technical report outlines the problems that can arise from poor planning, engineering and

execution of cement placement operations; it reviews the SBT logs of these wells and

possible reasons of cement placement problems. It aims to capture all the failure points

during cement placement operations and to increase the efficiency of the cased hole

completions, it then recommends that parameters like the circulation period (if there was

logging operations) should be increased, the drilling fluid should also be conditioned properly

alongside other recommendations to ensure good cement bonds.

BACKGROUND

Cement placement is a critical component of well architecture for ensuring casing mechanical

support, protection from fluid corrosion, and most importantly isolating permeable zones at

different pressure regimes to prevent hydraulic communication. It is also very necessary to

get good bonding behind the casing prior to perforation for Drill Stem Testing (DST) or

completion operations. The failure of cement placement could lead to immediate or later

problems of the well/s in question; this as we know was the cause of the single point failure

of the Macondo well.

The use of Cement Bond Logs (CBL) is very important so as to help inspect cement

placement and bonding behind the casing. The Cement Bond Log (CBL) gives a continuous

measurement of the amplitude of sound pulses from a transmitter to receiver. This amplitude

is maximum in unsupported pipe and minimum in well-cemented casing. The wave train can

be displayed as a Variable Density Log (VDL) where the positive and negative cycles of the

wave train are shaded black and white respectively. This was used to evaluate the cement

placement behind the 9-5/8” casing for the OML-126/137 wells used for this case study.

There are various reasons why there could be failure to having a good bond between the

casing and the formation. The classification based on this technical report was classed to be


either engineering based or operational based, or the investigations will be based on these

classifications reviewing all the possible routes of failure.

OPERATIONAL BASED FAILURES

The operational based problems can be defined as Rig site problems that tend to steer the

planned operations schedule from the original, they also could be problems that could arise

from the operator’s incompetence or lack or understanding of the operation. Some of these

problems include:

1. Cement unit failure

2. Human Error

3. Contaminants(Mix Water, Cement and Chemicals)

4. Incorrect Volume of Mix water and Chemicals

5. Spacer.

6. Poor Mud Characteristics

7. Poor mud circulation prior to cementing

8. Displacement rates.

9. Stress cracking of the cement sheath.

ENGINEERING BASED FAILURES

Engineering based failures are failures based on the design and simulation of the slurry, these

parameters, simulations and tests which are very important for engineering and simulation

purposes should be taken very important and should be reviewed in detail alongside the

practice. They include:

1. Ultrasonic cement analyzer and crush compressive cement simulation (UCA and

CCS).


2. Incorrect down-hole temperature.

3. Fluid loss.

4. Thickening time tests.

5. Fluid compatibility tests (Spacer, mud and cement).

6. Static gel strength.

7. Rheology

8. Foam mix and stability test.

9. Free fluid

10. Centralization program

INVESTIGATION AND STUDY

Five wells in the OML 126/137 were chosen for this study, details of the cementing

operations based on the records from the Daily drilling report, the geologic prognosis and

cement evaluation logs were used in analyzing the cementing operation. The wells considered

for the review include Okwori-22 (OML-126), Okwori-24HST (OML-126), Okwori-25

(OML-126) and Ofrima-4 (OML-137) .Their modes of operations were reviewed, and

possible sources of placement problems were highlighted.

OKWORI-22

The 12-1/4” hole section of the OK-22 well (see appendix a for well schematics) was drilled

to 9355ftMD/8530ftTVD with 48.33deg inclination and cased out with the 9-5/8”, L-80,

47ppf casing shoe was set at 9335ftMD/8528ftTVD (48.31deg inclination), the objective of

the 9-5/8” casing was to set the shoe below the OR-D and above the PI-A sands to isolate the

OR-A OWC, a good cement job was required to provide a good quality cement bond between

the formation and casing across the OR-A for potential future completion of the OR-A sands

(Cased hole completions). The following actual formation depths were made while drilling

the 12-1/4” hole section showing the top of the OR-A sands at 8253ftMD and its OWC at

8419ftMD.The figure below shows the predicted depths and actual sand depths.


TABLE 2: PROGNOSED AND ACTUAL SAND DEPTHS OF THE 12.25” HOLE SECTION OF THE

OK-22

It is worthy to highlight that between the termination of drilling the 12.25” hole and the

commencement of the cementing operation, there was a 65.75hrs of wireline logging

operations, two wireline runs (#1- Induction/Z-densilog/Compensated Neutron log/Gamma

ray log, #2-RCI log), after this logging operation a wiper trip assembly was RIH to tag 9344ft

(21ft fill) this fill was reamed out and BHA was ran back to bottom. Fifty (50bbls) of super

sweeps was pumped twice and circulated out with 790gpm.

It is also worthy to note that the casing running operation into a 12.53” gauged hole took

29.50hrs and there was 1.5 times bottoms up circulation with 455gpm prior to cementing

operations. The cement programme was designed such that 80bbls of 12.0ppg Tuned Spacer

was pumped this was followed by 117.4bbls of 15.8ppg Single slurry (10% excess) so as to

place the top of cement at 7765ft (500ft above the OR-A). This was performed and the

cement was displaced with 616bbls of sea water at 10bbl/min, the pump rate was slowed

down to 7bpm to bump plug with 5748strokes (622bbls). The final circulating pressure

observed prior to bumping the plug was 2454psi, the casing was pressure tested to 4000psi

for 10min, there were no losses observed during the cementing operation. This is shown at

the chart (figure 2) below:


FIGURE 1.19 OKWORI-22 9-5/8”CASING JOB CHART

To investigate the quality of cement sheath behind the 9-5/8” casing, an SBT log was ran, the

TOC was observed at 7600ft (7765ft-expected), but further inspection of the logs below

8420ft to 8490ft-OR-B sands) it was observed to be to have poor cement bonding (high

signal amplitude) with the OR-B sands but there was very good cement placement observed

(low signal amplitude) with the SBT logs at the region of interest (OR-A sands), figure 3

below shows the SBT log with the TOC at 7600ft.


Figure 1.20 SBT log showing TOC at 7600ft

The investigation as planned for this technical report which classed failures into Operational

based and Engineering based failures. This classification and the sub topics will be used as

anchor to investigate failures of the cement placement operations.

OPERATIONAL BASED ANALYSIS

1. Cement unit failure: There were no failures of the mixing and pumping unit reported

during this operation.

2. Human Error: The right volume of spacer and slurry were pumped and Halliburton

confirmed that the samples they received from offshore have the as planned

properties.

3. Contaminants: Halliburton also confirmed that from the samples they received there

was no contamination observed.

4. Mix-water and chemicals: Halliburton confirmed that the right amount of mix-water

and chemicals were used for the cementing operations.

5. Spacer: Adequate slurry was pumped ahead prior to the cement placement.


6. Mud characteristics: The Yield Point (YP) and Gel strength of the mud was reduced

as noticed from the Daily Mud report, the YP was reduced from 20lbs/100ft2 to

13lbs/100ft2, the Gel strength (10s/10m/30m gel) was reduced from 12/16/24lbs/100ft2

to 7/11/18lbs/100ft2.

7. Circulation prior to cementing operations: There were two bottoms up circulations

prior to logging operations, and there was logging operations for 65.75hrs, this

logging time might have deposited some of the weighing solids (Barite-which is a

cement contaminant) or some of the high gravity solids, this depending on the

thixotropic nature of the fluid, and if there was not enough turbulence to lift the solids

away from the walls of the formation we might not have been able to get good cement

around those areas where these solids have settled. There was further 29.50hrs of

casing running operations, and this should have increased time for the solids to settle

behind the casing, after landing the casing 1.5 times bottoms up was circulated at

455gpm (should we have increased the circulation rate and volume so as to have more

cleaning on the annulus?)

8. Displacement rates: The displacement rate was at 5bpm as simulated by the

OPTICEM, to ensure efficient mud displacement.

9. Casing test: The cement was tested when the cement was still green to prevent the

creation of micro-channels.

ENGINEERING BASED ANALYSIS

1. UCA and CCS simulations: This was performed prior to cementing operations, with

the slurry prepared with sample water from the rig location.

2. The right down-hole temperature (205degF) was used for the simulation, fluid loss

tests, thickening time tests and fluid compatibility tests were performed prior to

operation.

3. Centralization program: This was simulated prior to operations so as to obtain a 70%-

80% stand-off.

INFERENCE


1. The logging operation which occurred immediately after the 12-1/4” hole section lasted for

about 66hrs (time for high gravity solids to settle out in the well).

2. The wiper trip operations observed a 21ft fill, 2X 50bbls of super sweeps was circulated

after the reaming operations to bottom (was the circulation enough to clean the hole?).

3. The casing running operation lasted for 29.50hrs and 1.5 bottoms up with 455gpm (was

this circulation sufficient as well considering the time spent for logging and casing

operations?).

RECOMMENDATIONS

1. The CBL/USIT should be run in tandem and the section where to be completed

properly logged. This will enable us get a better view and analysis of the cement

placement behind the casing.

2. Prior to setting the seal assembly, the logging operation should be performed; this will

enable us to be able to perform remedial cementing after analysing the USIT/CBL

logs if not satisfied with the cement placement from the logs.

3. It should be considered having the samples sent from the Rig checked by the Addax

DE and Halliburton to confirm all the cement properties and annul any doubts of

human error.

4. If logging operations is performed in the hole section, there should be a longer

circulation time to ensure that the hole is properly cleaned prior to cementation.

5. The Yield Point and Gel strength should be properly specified in the Drilling

programme what it would be thinned down to prior to the casing operation to ensure

that the mud is properly displaced.

6. It is recommended that Halliburton involve a cementing expert in this investigation to

review the cementing practices and operations and advice appropriately for it is

mandatory that our cementing operations be improved to help the completions

strategies planned for the next phase of the Okwori field development.


APPENDIXWELL SCHEMATICS OF CASE STUDIES (Appendix a)

OKWORI -22 WELL INFORMATION AND SCHEMATIC

WELL NAME: OKWORI-22 ACTUAL WELL DATA

Surface Coordinates (UTM)

272891.97mE, 427809.25mN

Surface Coordinates (UTM) Lat. / Long.

3°52'04.767"N / 6°57'17.432"E

Projection System: WGS84 / UTM Zone 32 North

Country, License: Offshore Nigeria, OML 126

Prospect Area: Okwori Prospect

Well Classification: Development/Green well

Well Type: Deviated Well

Objective:Appraised the OR-A, PI-A, PI-B, PI-C and PI-D/E sands

and completed the PI-C Reservoir Sands.

Operator: Addax Petroleum Exploration Nigeria Ltd. (APENL)

Drilling Rig: Saipem Scarabeo 3

Elevation RT: 105ft Above MSL

Water Depth: 432ft Below MSL (537ft below RT)

Well TD (MD/TVD): 10,638ft / 9,385.8ft

Final Well Status: Completed the PI-C Sands.

AFE Number: D1126043

Actual Well Cost: $ 56,873,899

Actual Days Well: 66.29days

Final Rig Heading: 307.46deg

TABLE 4 OKWORI -22 WELL INFORMATION


OKWORI -22 WELL SCHEMATIC


1.3.5 MUD ENGINEERING UNIT (GEOFLUID&MI)

Drilling mud is one of the most important elements of any drilling operation. The mud has a

number of functions, which must all be optimised to ensure safely, and minimum hole

problems. Failure of the mud to meet its design functions can prove extremely costly in terms

of materials and time, and can also jeopardise the successful completion of the well and may

even result in major problems such as stuck pipe, kicks or blowouts.

There are basically two types of drilling mud. Water-based and oil based, depending on

whether the continuous phase is water or oil. Then there are a multitude of additives, which

are added to either change the mud density or change its chemical properties.

Drilling Fluid Functions

1. To cool and lubricate the bit and drill pipe

2. To control sub-surface pressures by providing hydrostatic pressure greater than the

formation pressure. This property depends on the mud weight, which, in turn, depends on the

type of solids added to the fluid making up the mud and the density of the continuous phase.

3. To remove the drilled cuttings from the hole.

4. To prevent the walls of the hole from caving.

5. To suspend the cuttings and weighting material when circulation is stopped

Drilling fluid Additives

There are many drilling fluid additives, which are used to develop the key properties of the

mud.

• Viscosifiers

• Filtration control materials

• Alkalinity and PH control materials

• Lubricating materials

• Shale stabilizing materials

• Lost circulation control materials

Drilling Mud Properties

The properties of a drilling fluid can be analysed by its physical and chemical attributes.

• Mud weight or mud density

• Viscosity


• Gel strength

• Yield point

Contaminations:

The vast majority of problems associated with drilling fluids can be directly attributed to the

detrimental effects of some type of contamination that enters the mud system. Contaminants

can be solid or liquid. E.g. NaCl,, Gypson, lime.

Role of Mud Engineer

• Takes inventory of mud chemical on the rig

• They formulate and mix the mud

• They carry out mud check and adjust mud properties according to drilling programme.

Role of mud engineer when tripping

• They monitor the trip tank

• Brings down the mud and reduces the viscosity of the mud for easy tripping

Role of mud engineer before cementing

• They assist the cementer in preparing spacer.

During Drilling

• They determine loses

MUD LOGGING UNIT

Mud Logging: This is the recording of information derived from examination and analysis of

formation cuttings made by the bit and of mud circulated out of the hole.

Formation Evaluation:

Determining whether a formation contains oil and gas falls under the realm of formation

evaluation. Formation evaluation includes the activities the operator does to test a formation

for hydrocarbons. The operator must not only know whether hydrocarbons exist, but also

whether they exist in ample amounts. A hole may penetrate a formation that contains

hydrocarbons.

Methods of formation evaluation include examining cuttings and drilling mud, well logging,

drillstem testing and coring.


Examining cuttings and drilling mud:

Several techniques are available to help the operator decide whether to complete the well.

One of the simplest is looking at the cuttings the drilling mud carries from the bottom of the

hole. The mud logger, use various kinds of detection equipment to spot hydrocarbons in the

drilling mud. An operator probably would not decide to complete or abandon a well using

only information from cuttings and mud returns. Careful examination of them, however, can

indicate whether the well is likely to produce. The mud logger analyse the lithology

description of the cuttings made by the bit to ascertain presence of hydrocarbon.

FIGURE 1.21 A handful of cuttings made by the bit.

Litholog: Measures and records the lithological description. Its records drilling

parameters like WOB, RPM etc. And also the kind of formation encountered e.g. shale or

sand.

Wireline Logs: Wireline logs are constant downhole measurements sent through the

electrical wireline used to help geologists, drillers and engineers make real-time decisions

about drilling operations. Wireline logs can measure resistivity, conductivity and formation

pressure, as well as sonic properties and wellbore dimensions.



A well-site log is interpreted to give information about the formations

CHAPTER 2

EXPERIENCE GAINED

The experiences gained during the course of the SIWES program include the following

Drilling engineering operations fundamentals (Rig Experience).

The Fundamentals of how the rig works.

Safety Awareness.

2.1 DRILLING ENGINEERING OPERATIONS FUNDAMENTALS.

Bit: the cutting element at the bottom of the drillstring, used for boring through

the rock.

Blow out: an uncontrolled flow of formation fluids into the atmosphere at

surface.

BOP: Blow Out Preventer. A valve installed on top of the wellhead to control

wellbore pressure in the event of a kick.

Bottom hole assembly (BHA: the part of the drillstring which is just above the

bit and below the drillpipe. It usually consists of drill collars, stabilisers and

variousother components.

Bottom hole pressure: the pressure either at the bottom of the borehole, or at

a point opposite the producing formation

Casing: large diameter steel pipe which is used to line the hole during drilling

operations.


Casing shoe: a short section of steel pipe filled with concrete and rounded at

the bottom. This is installed on the bottom of the casing string to guide the

casing past any ledges or irregularities in the borehole. Sometimes called a guide

shoe

Cement Slurry: A mixture of cement powder, water and additives which harden

to form a cement sheath or cement plug in a well.

Christmas tree: An assembly of control valves and fittings installed on top of

the wellhead. The Christmas tree is installed after the well has been completed

and is used to control the flow of oil and gas.

Cuttings: the fragments of rock dislodged by the bit and carried back to surface

by the drilling fluid.

Development well: A well drilled in a proven field to exploit known reserves.

Usually one of several wells drilled from a central platform.

Drag: The force required to move the drillstring due to the drillstring being in

contact with the wall of the borehole.

Drilling fluid: The fluid which is circulated through the drillstring and up the

annulus back to surface under normal drilling operations. Usually referred to as

mud.

Drill stem test (DST): a test which is carried out on a well to determine

whether or not oil or gas is present in commercial quantities. The downhole

assembly consists of a packer, valves and a pressure recording device, which are

run on the bottom of the drill stem.

Exploration well: A well drilled in an unproven area where no oil and gas

production

exists (sometimes called a "wildcat").

Kick: an entry of formation fluids (oil, gas or water) into the wellbore caused by

the formation pressure exceeding the pressure exerted by the mud column.

Mudlogging: The recording of information derived from the examination and


analysis of drill cuttings. This also includes the detection of oil and gas. This work

is usually done by a service company which supplies a portable laboratory on the

rig.

Torque: the turning force which is applied to the drillstring causing it to rotate.

Torque is usually measured in ft-lbs.

2.3 FUNDAMENTALS ON HOW THE RIG WORKS

Drilling an oil well is a massive project that involves teams of workers and specialists. Here

is a basic guide to the steps required to drill for oil.

1. Hire geologists to analyze the features of an area and see if it is likely to contain oil.

Geologists will analyze an area's surface features, terrain, and rock and soil types, as well as

the Earth's magnetic and gravitational fields. A number of methods are used to perform a

seismic survey, in which shock waves are sent through rock layers under the earth and later

analyzed. Hydrocarbons can be detected using electronic "noses" called sniffers.

2. Mark the targeted area for drilling. Place buoys around the area if it's in the water.

Use GPS coordinates to mark a designated spot when drilling on land.

3. Take the necessary legal steps. Obtain any permits, lease agreements, titles, etc.,

needed to drill in the area. Measure any impact the drilling will have on the environment.

4. Clear and level the designated area.

5. Ensure that a water source is nearby, as one is needed in the drilling process. If

there is no natural source of water, a well must be drilled.

6. Dig a reserve pit and line it with plastic. This pit will be used to dispose of rock

cuttings and drilling mud. Cuttings and mud will have to be trucked away from the site if

the drilling is being performed in an ecologically sensitive area.

7. Dig a rectangular pit, near the future spot of the drilling hole, to act as a workspace

for the drill crew. Dig any other necessary holes nearby for storing equipment.

Drill the Main Hole


1. Use a drill truck to drill a starter hole that is shallower and wider than the future

main hole. Line this hole with conductor pipe.

2. Drill the main hole with an oil rig, but stop before reaching the expected location of

the oil trap. Set the bit, collar, and drill pipe in the hole and attach the kelly and turntable

(the system that pumps the drilling mud). Start drilling, floating the rock cuttings out of

the hole.

You can drill hundreds or thousands of feet deep before reaching the oil trap. You will

need to add drill pipe and casing as you drill deeper.

3. Insert casing pipe into the hole.

4. Cement the hole to prevent collapse. Pump cement and drill mud through the casing

pipe with a cement slurry and a bottom plug. The cement will move through the casing

and fill the area between the outside of the casing and the actual hole. Let the cement

harden.

5. Stop drilling when the rock cuttings contain signs of oil sand from the reservoir

rock.Test rock samples, measure pressure, and lower gas sensors into the hole to

determine if the reservoir rock has been reached. Keep drilling if it has not.

Once You've Reached the Reservoir Rock

1. Lower a perforating gun to punch holes into the casing.

2. Run tubing into the hole for oil and gas to flow through to the top.

3. Seal the outside of the tubing with a "packer."

4. Control the oil flow. Connect a multi-valved structure (called a "Christmas tree") to the

top of the tubing.

5. Remove the rig when oil starts to flow.

6. Install a pump on the well head.


2.3 SAFETY AWARENESS. (SAFETY MEANS PROFESSIONALISM)

It’s always very good to be safety conscious on the rig like wearing personal protective

equipment like safety goggle, coverall, safety boot; hard hat etc. Sometimes flotation devices

like life jacket could be used depending on the area you are working.

An engineer well equipped.


I was required to submit daily safety observation cards on the rig. On the rig the culture is

‘’you see it, you own it’’. By so doing if you observe that one is not doing the right thing or

the task/operation the personnel is doing could pose a potential hazard on the personnel

involved, you are required to stop and correct the person. Then a documentation of such

observation is then submitted for review and during the next safety meeting it is discussed to

everyone so that people would be aware of such hazard thereby preventing future occurrence

by other personnel.

CHAPTER 3

CHALLENGES ENCOUNTERED

My mentors had limited time to put me through because they were always too

busy.

They had too many tasks at hand, this therefore limited the quality time they ought to

have spent teaching me and giving me various tasks.

Limited task due to sensitivity of operations/activities being carried out in both

office and on the rig.

Task such as drilling operation design, completion design, and rig operations were too

sensitive and hazardous thereby limiting my level of participation.

Too much to learn within a short period of time.

Especially on the rig, I had to stay extra hours and sleep say 4hrs out of 24hrs that

make up one day because most of the activities such as gravel packing, perforation,

casing run and cementing coincidentally occur at nights.


Cement surge-cannot taking suction after cement lead slurry has been pumped

downhole.

This occurred as a result of discharge line being plugged off. This operation had to be

manually done which was more stressful and time consuming.

Understanding the acronyms and abbreviations used in the industry.

At the beginning of the SIWES programme, a major challenge I encountered was

trying to decode the full meaning of different abbreviations I came across.

Inability to land casing hanger on wellhead after cementing.

I participated in the cementing job done and we had difficulty landing casing hanger

on wellhead due to differential sticking resulting.

CHAPTER 4

OBSERVATIONS AND CONTRIBUTIONS

During the course of my SIWES programme, after technically investigating and studying

company operations, and also being practically involved in the operations, the following

was observed:

Standard quality assessment and quality control (QAQC): As a company

procedure and ritual, the QAQC (quality assessment and quality control) department

always ensures that the best quality equipment and services rendered and always up to

specification.

Good Health Safety and Environment policy (HSE): At addax petroleum, safety is

not just a priority, it is the core value. I observed that safety is taken very seriously at

the offices, rigs and field as all workers must always wear the correct PPE (personal

protective equipment) when working. Before any job is to take place, the HSE officer


always ensures that all the risks are properly assessed and analyzed in order to ensure

a safe and smooth operation.

Very Conducive and friendly environment to work in: My department was full of

friendly individuals to work with and that were willing to share their knowledge and

help with mental problems. I was giving a work space with a computer as well as a

learning matrix and full access to the drilling.

During the course of the SIWES programme, I was privilege to offer my contributions in

some specific areas which include:

Health Safety and Environment: Under the safety section, I was given the task to:

Anchor the weekly HSE meeting: Anchoring the HSE meeting however involves

being the lead in the meeting, and taking everyone through the meeting to the

end, and also give my opinion on various HSE concerns. I also gave presentations

on various HSE topics.

Technical Report: I compiled a technical report on the cement sheath placement

behind the 9-5/8” casing of the Okwori wells. Its purpose was to review to enhance

cement sheath placement for efficient cased hole completions.

CHAPTER 5

CONCLUSION

It is very crucial and mandatory that all the proper steps and procedures are followed during

drilling and completion operations for the overall process to be successful, and also not

forgetting the importance of sand control mechanism, effective cement operation and

operative mud engineering in the completion process, so as to enhance maximum

productivity, and also reduce the cost of regular maintenance of both down hole and surface

equipment.

My internship experience was indeed superb and I would love to thank the school for such an

opportunity for students to see the practical application of most of what we are being taught

in school. It has given me a picture of what future demands are. I would love to encourage the

school and the industries to continue giving students this great opportunity.


CHAPTER SIX

CHALLENGES FACED BY INDUSTRY BASED FIRM

The SIWES programme exposed me to the various challenges that are encountered by the

company due to a variety of reasons.

Fishing: the process by which a fish is removed from the wellbore. A fish is any

object accidentally left in the wellbore during drilling or workover operations, which

must be removed before work can proceed. This halted drilling activities for days as

it simultaneously incurred cost for Addax.

Security Issues in The Niger delta: During my stay at Addax there was a case of

kidnapped Nigerian Oil workers as well as retaliations from the host community on


Addax’s land rig asset due to disagreements between parties in the community on

appropriation of funds.

Understaffing; There were many vacant positions in my department during my stay.

There were some reasons for the tardiness of the recruitment process but this put

many of the staff under pressure having to do extra work and make extra rig visits.

Too many Contractors-Addax has a lot of contractors and it does not have an

organized system to support their call offs, organized payments and tracking their

progress especially in the Lagos office.

Waiting on weather (WOW).

This was a major challenge both on the rig. It hinders setting of the cement slurry,

personnel transportation, equipment transfer from one place to another, offloading and

backloading from rig to vessel etc

REFERENCES

1. Nelms, L.T.: “Oil and Gas Reserves Evaluation,” PetroSkills, Tulsa, Oklahoma, 2930 USA (2005)

2. “Offshore Drilling and Completions Training Manual”. Drill Quip Inc, Houston, Texas 77040, USA

(1996).

3. Satter A., PhD: “Integrated Petroleum Reservoir Management”: Pennwell Publishing Company

4. Oyeneyin M.B., PhD: “Lecture Notes on Basic Petroleum Technology”. Shell Special Intensive

Training Programme (2004)

5. Society of Petroleum Engineers/World Petroleum Congress Reserves Definitions (1997)

6. Addax Petroleum S- Drive (database).
