CHAPTER 2
OFFSHORE OIL AND GAS DEVELOPMENT PROJECTS
2.1
Introduction
This chapter discusses the typical phases and activities involved in offshore
oil and gas development. The aim of this chapter is to provide an understanding and
appreciation of the activities and sequences of the events involved in the upstream oil
and gas development projects.
An understanding of the engineering activities and their relationship are
important in formulating the most appropriate delivery system for the project.
2.2
Offshore Oil and Gas Activities
By and large, Malaysia hydrocarbon reserves are located offshore, primarily
in the east cost of Peninsular Malaysia and also offshore of Sarawak and Sabah. In
order to realise the benefits of the hydrocarbons underneath the ocean, the
hydrocarbon must be extracted, processed and eventually marketed to consumers.
7
According to Graff (1981), oil operation conducted offshore can be broken
into five main areas, namely, exploration, exploration drilling, development drilling,
production operation and transportation. Walsh (2003) also identified four distinct
phases in the life cycle of offshore oil and gas fields, namely, exploration,
development, production, decommissioning / abandonment.
Therefore, in general, it can be said that offshore oil and gas development can
be summarised into three stages, namely, exploration, development and production.
2.2.1
Exploration
The exploration phase consists of activities involved in locating oil-bearing
strata within the ground underneath the ocean. Geologist and geophysicist are the
experts involved in the activities.
Geophysicist uses methods of remote data
gathering such as seismic exploration and instrumentation for measuring gravity
fields and make interpretation as to the possible presence of oil-bearing strata. He
will systematically survey the ground structure underneath the ocean, and when an
area thought to be favourable is found, sample cores are drilled for further
investigation. The Geologist then studies surface formations and core samples to
describe the geometry of the earth’s fault and strata and identifies the areas that may
contain oil-bearing strata.
Once it is decided that an area may contain oil-bearing strata, an exploratory
drilling need to be carried out in order to confirm or deny the presence of
hydrocarbon. The formation can yield gas or oil, or both. The exploratory drilling
also provides information on quantity and quality of the hydrocarbon. As such,
further analysis could be done to determine whether the reserves are commercially
feasible to develop.
8
2.2.2
Development Phase
The development of the offshore oil and gas fields begins when it is decided
that the fields contain producible amount of oil or gas. It is during this stage that
decisions are made on the types of facilities that are required to process the extracted
mixture of oil, gas and water and to transport the crude hydrocarbon products to
onshore for further processing. These facilities, such as, the necessary drilling and
production equipment, are normally contained on large permanent offshore
platforms. The types of offshore platforms commonly used for offshore oil and gas
development are discussed later in this report.
During this stage, much of the Oil Company’s efforts will be concentrating
on the planning and managing the contracts for the design, procurement of materials
and construction of the required platforms.
A project team will be set up to
undertake the tasks. The offshore platforms are normally constructed in fabrication
yard for cost savings and to facilitate construction. Once completed, the platforms
will then be transported offshore by barge to the final location for installation.
Developing oil and gas fields presents many difficulties and considerable
expense particularly in the offshore development. The less stable environment and
violent weather conditions pose unique problems for offshore development activities
has led to the development of specialised equipment and techniques. As such, a
proper project management strategy are evaluated and developed from the outset to
ensure that all the resources are appropriately expended.
2.2.3
Production Phase
Once all the platform facilities are successfully installed, hook-up and
commissioned, the facilities are then ready to be start-up and the production and
9
operation phase will begin. The extracted hydrocarbon will be processed from the
offshore platforms and transported onshore, through pipelines or ships, for further
processing and refining before they become consumable products. The facilities will
continue to produce and transport the crude hydrocarbon until it is no longer
economic, normally after 15-20 years. Then, the platforms will be decommissioned,
dismantled and removed from their locations.
2.2.4
Summary of Offshore Oil and Gas Activities
Phase 1
EXPLORATION
 Locating the oil
bearing strata
underneath the ocean
Phase 2
DEVELOPMENT
 Design, Construct,
Transport, Install,
Hook-up and
Commissioning the
facilities for extracting
the hydrocarbon from
underneath the ocean
Phase 3
PRODUCTION
 Extracting, processing
and transporting
hydrocarbon from
underneath the sea to
onshore for further
processing and
refining.
Figure 2.1: Summary Phases of Offshore Oil and Gas Activities
As earlier discussed, oil and gas formations are found deep underneath the
earth. In Malaysia, the oil and gas fields have been mostly found at offshore
locations. In order to realise the benefits of hydrocarbon underneath the ocean, the
fields must be developed. The main three phases of the offshore oil and gas activities
can be diagrammatically summarised as shown by Figure 2.1 above.
10
2.3
Offshore Oil and Gas Development Projects
The offshore oil and gas development projects take place during the
‘Development Phase’ of the overall oil and gas activities. The main objective of
such development projects is to provide offshore facilities for extracting, processing
and transporting the hydrocarbon onshore for further processing. The facilities to be
provided for that purpose are normally the offshore platforms and sub-sea pipelines.
This report will concentrate on the provision of offshore platforms. Types and
functions of the offshore platforms are discussed later in this Chapter 2.
Like other engineering and construction projects, a typical offshore oil and
gas development project covers a whole range of activities from its inception up to
ultimate realisation i.e. production of the oil and/or gas.
Traditionally, typical
offshore development projects will cover, inter-alia, the following activities:
Stage 1:
Design of Offshore Platforms
Stage 2:
Procurement of long lead materials and specialist equipment
Stage 3:
Construction of Offshore Platforms
Stage 3:
Transportation and Installation Offshore Platforms
Stage 4:
Offshore Hook-up and Commissioning of Offshore Platforms
Before we could discuss the above activities, it is essential that we understand
the types, functions and components of the offshore platforms.
2.4
Offshore Platforms
The range of offshore platform is very great.
In general, the offshore
platforms use in the oil and gas development projects can be firstly divided into two
11
types, namely, the steel template platforms and the concrete gravity platforms. Then,
they can be further sub-divided according to construction or their functions. To date,
all the platforms constructed and installed offshore Malaysia are of steel template
type.
According to Graff (1981), economics control the specific choice of
platforms to be placed at a given offshore location. In deep water (approaching 400ft
or 122m), a self-contained platform would be most advantageous. Self-contained
platform combines all functions on one multilevel structure.
On the other hand, in shallow water development, it is advantageous to
separate the functions and have several separate platforms. These platforms can be
collectively divided into the following functional types:
2.4.1
1.
Drilling Platforms
2.
Production platforms
3.
Quarters Platforms
4.
Flare / Vent Platforms
5.
Heliport and Bridges
6.
Self-contained Platforms
Drilling Platforms
Drilling platforms are used for production drilling. Generally, the drilling
derrick and substructure, drilling mud, primary power supply and mud pumps are
placed on the platform. The drilling crew quarters, remaining equipment, and
supplies are located on the tender barge moored adjacent to the platform. The two are
usually connected by a long walkway or gangway.
12
2.4.2
Production Platforms
A production or processing platform is basically a platform for separating the
oil-gas-water mixture of the produced crude hydrocarbon into crude oil, natural gas
and water; and treating each of these by simple in the field processes, prior to
transporting the product onshore for further processing.
The processing facilities on a particular production platform may vary
depending on what is to be done with the crude oil and/or natural gas, whether the
they are to be off-loaded into tankers or pumped ashore through pipeline. Sometimes
there are facilities on the platform for injecting pressurised water into the oil bearing
strata within the earth to improve the production.
If the products are to be transported offshore via pipelines, there should be
two pipelines from the platform to shore, one for crude oil and one for natural gas.
The platform must also have two sets of metering and shipping equipment. Pumps
send the crude oil through strainers, then through meters and into liquid pipeline.
Compressors send the natural gas through strainers, then meters and into gas
pipeline.
For each system, there are meter calibrations or test-loops, recording
instruments and sphere launchers to force cleaning devices through the pipelines.
These cleaning devices or better known as pigs, are spheres of hard rubber,
somewhat larger in diameter than the pipeline through which they are to pass. They
are inserted into the pipeline through by-pass loop in the line and are forced along the
pipeline through by the pressure of the compressed gas or liquid behind them.
If they is no gas pipeline the natural gas is usually burned off through a flare
tower remote from the production facilities on the platform. For some self-contained
platforms, the flare tower is part of the deck. However, when water depths permit it
is safer to mount the flare tower on a separate jacket remote from the treatment plant.
13
Apart from the above processing facilities, production platform also include
equipment for separation of the natural gas from the liquid mixture and water.
Usually, some of the separated gas is used to power the gas turbine generators. The
pumps and compressors on platforms are normally electric driven.
2.4.3
Quarters Platform
The living accommodation for offshore workmen is commonly known as
‘quarters’ platform. For economic reasons, in deepwater, about 100 m deep, the
quarters are made as an integral part of the single platform.
In more shallow water, the living quarters may be separated from the drilling
or production activities as a matter of crew safety. The living-quarters platform is
normally, connected to the drilling or production platform and is connected by a
bridge. The quarters platform are typically equipped with the facilities, such as,
bedrooms, dining hall, kitchen, change room, radio room, hospital room, laundry
room.
2.4.4
Flare / Vent Platforms
The function of vent platform is to release the access gas and/or hydrocarbon.
Like the quarters platform, the may be separated from the drilling or production
platform activities, in shallow water development. In this instant, they are normally
installed more than one kilometre away from the main platform. The access gas
and/or hydrocarbon are release through sub-sea pipeline connecting the main
platform with the vent platform.
14
On the other hand, in deeper water, the vent towers are integrated with the
main platform. In this instant, the vent towers could reach as high as one hundred
meter above the top deck of the platform.
2.4.5
Bridge and Helideck
A bridge or catwalk serves as a link between two neighbouring offshore
platforms for pedestrian movement. However, in most instances, a bridge may also
serve as supporting structure for pipeline and utility cables linking the platforms.
Bridges are normally found in shallow water complex where various types of
platforms are installed and connected together. In deeper water, self-contained
platform will be more likely used.
Helideck would be required if the offshore crew are to be transported via
helicopters. Helideck are normally constructed on top of living quarters. Graff (1981)
suggested that, when the distance to offshore location is approximately 50 miles (80
km) or less, offshore crews are transported by boat. When the distance is more than
50 miles, helicopters are used.
Graf (1981) further listed the following advantages of using helicopters for
transportation of work crew to offshore platforms:
1.
Considerable time saving and, therefore, reduction in cost. A
helicopter cuts travel time to about one-sixth of that by boat.
2.
Transfer between boats and the offshore platform are sometimes
impossible in high seas. Helicopters reliability and capability in the
weather are much better.
15
3.
Boat-delivered crews sometimes arrive seasick and ill-prepared for
work – not so for helicopter transported crew.
4.
Supervisors and specialist can hop quickly from shore to platform and
back, accomplish their job more efficiently.
5.
Emergency repair parts can be obtained more quickly; geological
specimen can be more rapidly taken to shore for analysis.
6.
Injured man can be flown to hospitals on shore.
7.
Rapid evacuation of the platform is possible in the event of an
emergency or severe storm.
2.4.6
Self-Contained Platforms
Self-contained platform, as its name suggest, is a large multiple decked
platform, with adequate strength and space to support the entire drilling rig, its
auxiliary equipment, living quarters, and vent / flare tower. It also has the facilities to
stock enough supplies and materials to last through the longest anticipated bad
weather when supplies cannot be brought in.
There are two types of self-contained platforms, namely, the template type
and the tower type. The different between the two types is the way the piles are
driven.
The ‘template type’ platform consists of a large multi-level deck structure
supported by long piles driven deep into the ocean floor. The template, also known
as jacket, is a three-dimensional welded frame of tubular members and is used as a
guide for driving piles through the hollow legs of the jacket. The jacket also holds
the piles together so that they act as a single unit against all lateral forces.
16
Early template structures had many legs and a multiplicity of horizontal and
diagonal braces. More recently, with the availability of very large tubular, the trend
is toward the eight piles type of platform. The jacket legs are not vertical. They
actually battered out. Normally, the battering is about one in seven or eight for the
legs on the long sides and one in ten for legs in the narrow dimension of the jacket.
The ‘tower type’ template platforms is characterised by relatively few large
diameter, non-battered legs and fewer diagonal braces of larger sizes than those used
in regular template type structures. The tower type jacket was conceived to eliminate
the need to launch the structure from the barge; it can be floated to location using
buoyancy of its larger-diameter legs.
17
Figure 2.2: Typical Steel-Piled Self-Contained Drilling/Production Platform.
Source: Introduction to Offshore Structures, W.J. Graff
18
2.5
Components of Offshore Platforms
Figure 3-2 shows the schematic design of a self-contained platform indicating
the various components. Generally, there are three major components of steel
templates platforms, namely, the Jacket, Piles and Topsides Facilities.
2.5.1
Jacket
Jacket is also known as substructure. It is the bottom section that submerged
below the sea level. It is the most critical to the entire platform, as it has to carry all
the dead loads of the platform as well as live loads. As such, most of the design effort
is spent on this component. It comprises of large diameter tubular legs framed
together by a large number of smaller tubular members called braces.
Jacket legs are not vertical. From end elevation, the legs are battered out to
provide a larger base for the jacket at the mud-line and thus assist in resisting the
environmentally induced overturning moments.
Depending on the type of platform, the appurtenances of a jacket include the
boat-landing, riser protection frame, launch runners, drilling conductor guides and
riser guides and clamps.
19
2.5.2
Piles
The Jacket structure is fixed to the sea bed using piles. The pile foundations
used offshore by the oil and gas industry are designed for loading conditioned
substantially greater than those onshore. Large lateral forces on the combined jacket
and pile structural system, imposed by waves and wind required that the piles to
penetrate the great distances into the earth underneath the ocean. The penetrations in
range of 76 – 122 m are common. As the piles usually installed through the jacket
legs, the total pile length may easily exceed 183 – 244 m.
The piles also vary in wall thickness. The largest wall thickness occurs in the
area of highest bending stress from a short distance above the mud-line to a
considerable depth below the mud-line. The cross-section of the piles is also thicker
at its tip as it serves as a driving shoe.
2.5.3
Topsides Facilities
The type and size of the topsides will very much depend on the function of
the platform. If the platform is a drilling platform, the topsides would have the
drilling facilities. A Quarters Platform would have living-quarters module etc. A selfcontained platform would have all the facilities like Power Generation and Utility
module, Quarters module, Production module, Drilling modules as well as the
Helideck and Flare Tower.
In principle, all topsides structures are made of three-dimensional steel
elements. The primary load-carrying members may be classified as plate girders, box
girders or trusses.
20
Topsides facilities can be categorised into two groups, namely, integrated
topsides and modular topsides. In the integrated deck system the all the equipment,
piping and electrical facilities are readily installed, hook-up and commissioned
during the construction of the deck. The advantage of integrated system is that all the
commissioning work can be carried out onshore, thus, minimise the offshore
duration. Nevertheless, due to its heavy weight, the deck would require a heavy
lifting barge to install the topsides. In the absence of heavy lifting barge, the
integrated deck could be installed by ‘float-over’ method.
In the modular system, the facilities are constructed in individual smaller
modules. It will normally consist of Module Support Frame, power generation
module, utility module, production module and quarters module. The modules are
then assembled, hook-up and commission offshore during the installation. The
advantage of this system is that heavy-lift barge would not be required. However, the
main disadvantage is that the offshore work would require longer duration and likely
to be more expensive.
2.6
Sequence of Activities in Offshore Oil and Gas Development Projects
As discussed earlier, the offshore oil and gas development project involved
design, fabrication, transportation, installation, hook-up and commissioning of
offshore platforms for extracting and processing hydrocarbon. In most instances, it
will also include the installation of sub-sea pipelines for transportation of oil and gas
to onshore facilities for further processing.
The offshore oil and gas development projects activities can be broken-down
into the following:
a)
Design Platform (Substructure and Topsides)
b)
Procurement of Specialist Equipment and long-lead materials
21
c)
Fabricate Platform (Substructure and Topsides)
d)
Transport Platform (Substructure and Topsides) to offshore location
e)
Install Platform (Substructure and Topsides) at offshore location
f)
Hook-up and Commissioning of Platform
Figure 2.3 below, shows a typical schedule for offshore oil and gas
development projects. The schedule is based on the traditional method, which
indicates the relationship and sequence of activities involved.
Figure 2.3: Typical Schedule for Offshore Oil and Gas Development Project
2.6.1
Design of Offshore Platforms
Offshore oil and gas platforms are specialised and uniquely developed
structures to serve special purpose. The concept and design of offshore platforms are
based almost entirely on the method of installation of the structure at the offshore
location i.e. either by lifting or float-over.
22
The structural aspects of offshore platform are designed to withstand the
environmental and operational loads. In addition, they must also be designed to
withstand the forces imposed on them during fabrication, load-out, transportation to
offshore location, and launching or lifting from the barge into final position.
Other engineering disciplines of the platforms are also need to be designed
during the design stage. They are:
2.6.2

Piping

Mechanical Equipment

Electrical

Instrumentation

Fire and gas.

Architectural
Construction of Offshore Platforms
Upon substantial completion of the detailed design, the construction or
fabrication phase will commence. The offshore platforms are normally constructed
in ‘fabrication yard’ for cost savings and to facilitate construction. Once completed,
the platforms have to be transported offshore by barge to the final location. List of
major fabrication contractors registered with PETRONAS are:
1.
Penang Shipyard Sdn. Bhd.
2.
HL Engineering Sdn. Bhd.
3.
Malaysia Shipyard and Engineering Sdn. Bhd.
4.
Sime Sembcorp Sdn. Bhd.
5.
Ramunia Fabricators Sdn. Bhd.
23
6.
Brooke Dockyard and Engineering Sdn. Bhd.
The sequences of the construction will very much a reflection of the offshore
installation sequence. Typically, the fabrication sequence will be as follows:
2.6.2.1
(a)
Jacket and piles
(b)
Topsides modules
Jacket and Piles Fabrication
The substructure’s fabrication will normally start first, followed by the
topsides fabrication. The substructure construction is mainly built-up of steel. Its
fabrication will begin with the procurement of long lead-time steel materials from
steel mill or supplier. Steel plates for rolling or forming thick-walled tubular are
ordered in specific dimensions to produce the required tube sizes with minimum
waste.
Prior to beginning the fabrication of the jacket, two parallel skid runners or
beams must first be constructed perpendicular to the quayside and extending far
enough away from the quay edge to accommodate the height of the jacket. The skid
runner must be placed on very firm foundations capable of supporting the final jacket
weight without imparting detrimental differential deflections on the surface as it
slides on its way to the launch barge during load-out. The jacket legs are then placed
on levelled pedestal or blocks in proper position for installing the braces. As many of
the jacket components as possible are fabricated lying horizontally on the ground.
Each major planar or bent across the narrow dimension of the jacket is fabricated flat
on the ground.
The first two panels to be built are the two that have parallel launch trusses
attached to the sides of the jacket legs. Upon completion these two panels are rotated
upright and placed on the skids of the skid beams. This position causes the
24
substructure, when completed, to lie on its sides with the legs that contain the parallel
launch trusses mated with the skid beams embedded in the ground of the fabrication
yard.
The skid beams are faced with heavy timbers before the first two panels are
put in position. The first panel is held in position with guy wires; the second is also
held by guy wires before installation of the braces between braces begins. The braces
are held in place by cranes. The joints are connected by welding. At this position, the
fitters and welders will be working from scaffolding or out of baskets supported by
cranes. If the full length of the panel is too heavy to be rotated into the vertical
position all in once, then it broken down into sections, and rotated section by section.
The sections are then rotated into vertical positions and welded end-to-end.
Fabrication of the jacket braces started as soon as the steel tubulars are
available. The fabrication work is normally done on special racks. The pipes are
place on the racks and the specified distance between the end patterns is measured
off. As the fabrication of the braces is completed, they will be marked and move
nearer to the substructure fabrication area. They are now ready to be lifted and
assembled onto the overall substructure.
While the jacket is being fabricated, many smaller ancillary structures are
also being fabricated, such as, conductor guide and framing, piles guides, boat
landings, walkways, buoyancy tanks, piping component for the decks, pipeline riser
guides, handrails, lifting eyes, stiffener rings for the jacket etc. Upon completion of
these items, they will be assembled onto the jacket structure.
The fabrication of pile sections is relatively straight forward. Piles are made
of high strength large steel plates, up to 75mm thick. The plates are rolled to form
large diameter tubulars about 3m long each. These tubulars are then jointed end to
end to form pile sections.
The fabrication of pile sections is normally carried out on a horizontal
rotating rack. The racks contain rollers so that tubular pieces can be rotated relative
to each other. Each sections must not be jointed together with the longitudinal weld
25
align to each other. Upon completion, the pile sections are marked and put in storage
until time for loadout to transportation barge for offshore installation.
2.6.2.2
Fabrication of Topsides Modules
The construction of the topsides modules begins with the fabrication of the
Module Support Frame (MSF). Modules Support Frame is the structural portion that
is attached to the substructure by stabbing cones. The topsides facilities will then be
installed on the deck of the MSF.
The structural members of facility modules may be fabricated in many ways.
Generally, the structural members will be fabricated and assembled as much as
possible. Then, the members will be blasted and painted.
Once most of the structural members are erected and painted, the major
equipment, piping spool and other utilities will be installed and incorporated within
the structural shell.
2.6.3
Transportation and Installation
Once all the fabrication of all the major components i.e. jacket including
appurtenances, piles and topsides facilities have been completed, they are then ready
to be transported to the final location for installation.
In Malaysia, all the components are normally transported to offshore by
barges. At fabrication yard, a completed jacket is normally loaded out onto
26
transportation barge by skidding. In recent time, load out by boggy are relatively
common. Other components, such as piles and topsides modules are normally loaded
out by lifting onto the barges. There will be a total of four transportation barges i.e.
one barge for the jacket, one barge for the piles and appurtenances, one barge for
module support frame and the final barge for the facilities modules.
Upon completion of the loadout operation, the components will then be
appropriately secured to the barges. This is called seafastening. As soon as all the
activities of seafastening of the structures to the barges completed and certified by
the Marine Warranty Surveyor, the barges and its cargoes may start the journey to
the final offshore location.
Typically, the journey to the offshore location will take about one week. On
arrival at the final location, the Jacket will first to be installed. The jacket will be
launched from the barge. It will then be up-ended using crane or derrick barge. At
this position, the jacket legs will slowly be filled up with water and the jacket slowly
submerging into the ocean.
Once the bottom of the jacket reached the sea bed, the jacket will be levelled
and the piling to its final position will commence. The piles will be driven by a large
hammer one by one until they reached at the desired penetration. After all the piles
are driven, the areas between the piles and the insides of the guides will be grouted.
The grout produces a permanent bond between the piles and the jacket, which creates
a single, rigid structure. The pile ends extending out of the tops of the jacket legs are
cut off to ensure that the topsides facilities on top will be levelled.
Once the jacket installation is completed, the topsides facilities will be
installed. The Module Support Frame will be the first to be installed. It will be lifted
from the transportation barged and installed on top of the jacket. The four points
which the MSF’s columns jointed to the jacket legs are known as the docking points.
Once properly aligned, they will be welded together. The facilities modules will then
be lifted one by one and installed on top of the module support frame.
27
2.6.4
Offshore Hook-up and Commissioning
Once all the modules are installed, the utilities and services of all the modules
are linked to each other. This activity is termed as hook-up. All the equipment and
system are then commissioned. Check and test that they are functional. It is also
during this period that all defects and incomplete work are repaired and made
complete. Upon completion, the platform is ready for start-up and to be handed over
to the operation team.