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Department of Petroleum Engineering and Applied Geophysics

TPG4140 Natural gas

Gorgon Natural Gas Project

Lucia COLOMBO Marie CURSAN

Lorenzo DELLORTO Carlo PICCINELLI

Luca RIBOLDI

Trondheim, November 2010.

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Abstract This report deals with the description of Gorgon Project. This is about a natural gas field

discovered in the Eighties about 130 km off the north-west coast of Australia. It is peculiar

for its huge dimension, about 40 Tcft of gas resources, and because of the infrastructure that

are under construction to develop the field. It will have a LNG treatment plant characterized

by three trains capable of producing 15 millions tonnes per year totally. All the facilities will

be developed on Barrow Island, 85 km off the coast, so there will not be any offshore

infrastructure : this will reduce all the costs and risks linked to that. Moreover, it will have a

Capture and Carbon Storage System, in order to cut off the emission of greenhouse gases

produced in LNG gas treatment. Thanks to the great dimension of this project, lots of new

jobs will be created and the global australian economy will grow up. Apart from the technical

challeges that this project has to face with, there is also the environmental aspect, which is

fundamental : Barrow Island is a Class A Natural Reserve and for this reason it has to be

preserved, in order to prevent any change and avoid any risk on the living species.

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List of Contents Introduction .........................................................................................................................................1 1. Gorgon Plant Overview...............................................................................................................2

1.1 Project history and overview ..................................................................................................21.2 Onshore and offshore infrastructures .....................................................................................31.3 Subsea infrastructures.............................................................................................................4

2 Geology..........................................................................................................................................5

2.1 Regional Geology of the Northern Carnarvon Basin Outline ................................................52.2 The Greater Gorgon Project ...................................................................................................52.3 The Gorgon Field....................................................................................................................62.4 Carbon Dioxide storage ..........................................................................................................6

3 Gas Processing and LNG Production ........................................................................................8

3.1 Inlet Processing.......................................................................................................................83.2 Acid gas removal and CO2 compression ................................................................................93.3 Dehydration and mercury removal .........................................................................................93.4 Liquefaction process.............................................................................................................103.5 Fractionation.........................................................................................................................103.6 End flash, nitrogen rejection.................................................................................................113.7 Power and thermal facilities .................................................................................................113.8 LNG storage and loading......................................................................................................11

4 Environmental concerns............................................................................................................12

4.1 Environmental Significance of Barrow Island .....................................................................124.2 Quarantine Expert Panel .......................................................................................................124.3 Construction Dredging Environmental Expert Panel ...........................................................134.4 Marine Turtle Expert Panel ..................................................................................................134.5 Environmental Approval ......................................................................................................144.6 Atmospheric Emissions ........................................................................................................14

5 Gorgon Project Economy..........................................................................................................16

5.1 Economic growth - National and local benefits ...................................................................165.2 Innovative Marketing Approach...........................................................................................175.3 Downstream contracts ..........................................................................................................185.4 The Gas Market Australia opportunities ...........................................................................19

Conclusions ........................................................................................................................................20 References ..........................................................................................................................................21 Bibliography ......................................................................................................................................23 Appendices .........................................................................................................................................38

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List of Tables Table 2.1 - Greater Gorgon fields reserves.........................................................................................24Table 2.2 - Key elements of the Proposed Gorgon Development ......................................................24 List of Figures Figure 1.1 - Main structures of Gorgon plant.....................................................................................25Figure 1.2 - Subsea equipments .........................................................................................................26Figure 2.1 - Structural elements of the Northern Carnarvon Basin and adjacent basins, oil and gas accumulations and selected wells .................................................................................................27Figure 2.2 - The Greater Gorgon Project fields..................................................................................28Figure 2.3 - Geography of Gorgon Field and Barrow Island .............................................................29Figure 2.4 - Gorgon classification ......................................................................................................30Figure 2.5 - Geo-sequestration of CO2 ..............................................................................................30Figure 3.1 - Location of the gas treatment plant in the Barrow Island...............................................31Figure 3.2 - Gas Treatment Plant Block Flow Diagram.....................................................................32Figure 3.3 - Slug Catcher ...................................................................................................................33Figure 3.4 - MEG regeneration loop ..................................................................................................33Figure 3.5 - Acid Gas Removal Unit (AGRU)...................................................................................34Figure 3.6 - Acid Gas Removal and CO2 Injection System Block Flow Diagram............................34Figure 3.7 - APCI 5 MTPA Refrigeration Cycle ...............................................................................35Figure 3.8 - C3MR Process ................................................................................................................35Figure 4.1 - Greenhouse Gas Emissions Efficiency Improvements...................................................36Figure 5.1 - National Gross Domestic Product and WA Gross State Product ...................................36Figure 5.2 - Employment trend ..........................................................................................................37 List of Appendices Appendix 1 - Gorgon Subsea Development.......................................................................................38Appendix 2 - Geology of DUPUY formation and CO2 Storage ........................................................39

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Introduction: With a rapid increase in the demand for energy and hydrocarbons it is important to find new

ways to cover the world primary energy supply. As an alternative to oil, natural gas is more

energy intensive and far less polluting which makes it more attractive, also because of less

CO2-emission. Further the use of LNG is predicted to rise in the years to come, due to its

attitude to be easily stored and economically transported over long distances.

The Gorgon gas project is a petroleum project in Western Australia, in the Northern

Carnarvon Basin , involving the development of the Greater Gorgon gas fields, subsea gas-

gathering infrastructure, and a liquefied natural gas (LNG) plant on Barrow Island. The

project also includes a domestic gas component. It is currently under construction.

This report would provide a complete description of the Gorgon gas project. An explanation

of every aspect of the field, how they are connected and developed and the several challenges

to overcome; pointing out the importance of a plant that once completed will become

Australia's fourth LNG export development.

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1. Gorgon Plant Overview

1.1 Project history and overview

Oil was discovered on Barrow Island in commercial quantities in 1964 by West Australian

Petroleum Pty Ltd (WAPET), and the first oil field was established shortly after. In 1995,

there were 430 wells producing oil and natural gas across most of the southern half of the

island. The site has been Australia's leading producer of oil. More than 200 exploration wells

have been drilled in the Barrow sub-basin over the past 35 years, including West Tryal Rocks

in 1972, and Spar in 1976 - both discovered by West Australian Petroleum (WAPET) which

had been a pioneering company in the development of the Western Australian petroleum

industry.

WAPET discovered Gorgon in 1981 with the drilling of the Gorgon 1 well. Later discoveries

included Chrysaor (1994) and Dionysus (1996). The Jansz-Io gas accumulation, discovered in

January 2000, contains an estimated 566 billion cubic meters of recoverable reserves. The

project received preliminary environmental approvals from the West Australian government

in September 2007 and from the Federal Minister for the Environment in the following

month. The project developers then submitted revised plans to cover an expansion in the size

of the project. Final environmental approval was received from the state government on 11

August 2009. On 26 August 2009, the Federal Environment Minister announced that the

expanded project on Barrow Island had been given conditional environmental approval

(Department of Resources, Energy and Tourism, 2008). The first LNG production is expected

in 2014.

The foundation development of the project includes:

Gas production from sub-sea facilities in the Gorgon, Io and Jansz fields located in the

Greater Gorgon Area, 130 200km from the coast in waters up to 1350 meters deep.

Sub-sea pipelines from these fields to Barrow Island.

A 6 MSm3 per day domestic gas plant and a pipeline from the island, 70 km offshore, to

join Western Australias onshore domestic gas supply.

Three Liquefied Natural Gas (LNG) trains, each capable of producing five million tonnes

annually on Barrow Island.

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LNG shipping facilities to handle about three shipments each week for international

markets.

Greenhouse gas management through CO2 injection into a deep geological formation

beneath Barrow Island.

1.2 Onshore and offshore infrastructures

The main infrastructures of the Gorgon plant are shown in Figure 1.1. Terrestrial

infrastructures associated with the Gorgon Gas Development consist of the following: [1]

Construction Village. Administration and Operations Complex. The permanent Utilities Area located within the Gas Treatment Plant. The Utilities Corridors between the Utilities area and users within the Gas Treatment Plant and between the Utilities area and the Construction Village, also servicing the Administration

and Operations Complex.

Road Upgrades, including road between WAPET landing and Town Point, and from Town Point to the Airport (via the Construction Village), and road along the feed gas pipeline

system route.

Airport Modifications, consisting of extension of the existing runway to the south and associated vegetation clearing.

Communications, consisting of a microwave communications tower and associated communications infrastructure to be installed on Barrow Island.

Onshore water supply infrastructure, consisting of a seawater demineralisation (reverse osmosis) plant, associated treated water and brine storage tanks, and treated water pumps and

delivery piping to end users within the Gas Treatment Plant.

LNG 2.1 kilometres jetty: it is a structure at the interface between onshore activities and sea transport. This jetty will allow ships to safely approach, vessels to safely depart and will

permit the transportation of goods and personnel. For these reasons, a particular attention is

paid on this jetty. Its design will either be a traditional piled structure or an alternative option

currently under consideration.

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1.3 Subsea infrastructures The development of the Gorgon Field is a great challenge. First of all, the nature surrounding

the Barrow Island has to be protected in order to prevent any kind of damage in the territory

and to the species that are living on. Secondly, the project deals with a subsea gas-gathering

system located from about 200 to 1300 meters deep that will deliver the well-gas to the

treatment unit on Barrow Island. In this case, the main innovation is due to the fact that all the

offshore facilities will be in the seafloor with no initial need for any permanent surface

facilities. The elimination of platform reduces the safety risks associated with helicopters by

avoiding the need for personnel to be permanently based offshore, or periodically required to

visit the platform. It also avoids emissions associated with operation on the platform and

significantly reduces overall capital costs by improving the international competitiveness and

overall viability of the project.

Up to 25 subsea wells will be drilled in the Gorgon field throughout its life. Subsea

equipments are shown in Figure 1.2. Each group of wells will use well jumpers to connect

them to cluster manifolds with between one and eight wells. Intrafield flowlines will then

transfer fluids to the export feed gas pipeline. Each production well will have a subsea

horizontal tree (7x 2) that provides containment and control. This will be installed prior to

installing the well completion. The reservoir section will be drilled with an 8.3/4 open hole

section and then lined with a 7 liner (Appendix 1). In addition to the line hanger, the liner

will feature a liner top packer. Once the completion is installed and pressure tested to satisfy

well integrity requirements, the reservoir will be perforated using guns deployed on wireline.

[2]

The production fluids (gas, water and some condensate, with production chemicals) will then

be piped to Barrow Island via a 70 km subsea feed gas pipeline(s). Feed gas pipelines will be

corrosion resistant alloy (CRA) clad carbon steel or carbon steel. . The total well flow rates

could range from less than 13 Sm3/s to more than 110 Sm3/s (40340 million standard cubic

feet per day (MMscfd)), with flow reducing over time as reservoir pressure declines [3].

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2 Geology

2.1 Regional Geology of the Northern Carnarvon Basin Outline The Northern Carnarvon Basin is the southernmost of the late Paleozoic to Cenozoic basins

comprising the Westralian Superbasin that underlies the northwestern continental margin of

Australia. It is bounded to the northeast by the Roebuck and Offshore Canning basins, to the

southeast by the cratonic Pilbara Block, to the south by the Southern Carnarvon Basin, and to

the northwest by the Argo, Cuvier and Gascoyne abyssal plains. The basin is predominantly

offshore, covering an area of approximately 535000 km2 in water depths of up to 3500 m.

Structural elements of the Northern Carnarvon Basin and adjacent basins, oil and gas

accumulations and selected wells are shown in Figure 2.1.

As one of Australias most explored and a prospective basin, the Northern Carnarvon Basin

has ready access to established oil and gas exploration, production and support infrastructure.

Projects developed to date include: Barrow Island (oil); the North West Shelf Venture

incorporating the North Rankin (gas), CossackPioneer FPSO (oil and gas), Goodwyn (gas)

and Angel (gas) production facilities; Airlie Island (oil); Varanus Island (gas and oil);

Thevenard Island (oil and gas); MutineerExeter FPSO (oil); StybarrowEskdale FPSO (oil

and gas); Enfield FPSO (oil), and; Vincent FPSO (oil). The newest and largest natural gas

project is the greater Gorgon project [4].

2.2 The Greater Gorgon Project Greater Gorgon refers to a grouping of several gas fields, including Gorgon, Chandon,

Geryon, Orthrus, Maenad, Eurytion, Urania, Chrysaor, Dionysus, Jansz/Io, and West Tryal

Rocks, situated in the Barrow sub-basin of the Carnarvon Basin.

The fourteen Greater Gorgon gas fields have gas reserves of 1,250 BCM with Gorgon, Jansz

and Io containing 80 percent, as we can see in Table 2.1. All fields except Gorgon are in deep

water further offshore and have 60 percent of the gas reserves. 60 percent of the fields have

gas reserves of less than 100 Bcm. 75 percent of condensate reserves are in Gorgon and Clio

[5]. A clear disposition of every field in the Greater Gorgon Project is shown in Figure 2.2.

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2.3 The Gorgon Field The Gorgon field, on which we are focusing, is centered about 130 kilometres (81 mi) off the

north-west coast of Western Australia, where the water depth is approximately 200 m (660ft).

In fact, as mentioned above, it is the only field in shallow water (other fields depth can be up

to 1300 meters). The gas processing part of the project is located on Barrow Island. Location

of some of the Greater Gorgon gas fields in relation to Barrow Island and the adjacent

coastline. Barrow Island lies off the Pilbara coast, 85 kilometres (53 mi) north-north-east of

Onslow and 140 kilometres (90 mi) west of Karratha. The largest of a group of islands which

include the Montebello and Lowendal Islands, it is 25 kilometres (16 mi) long and 10

kilometres (6.2 mi) wide, covering 235 square kilometres (91 sq mi) [6]. The geography of

the Gorgon field and the Barrow Island is shown in Figure 2.3.

Other fields in the group lie to the north, such as Jansz-Io, which covers an area of 2,000

square kilometers (770 sq mi), in a water depth of 1,300 meters (4,300 ft). The Gorgon and

Jansz-Io gas fields, are said to contain 40 trillion cubic feet (1.110^12 m3) of natural gas and

may have a lifespan of 60 years. While the natural gas in the Jansz field contains less than 1%

carbon dioxide, the Gorgon field gas contains 15 mol% CO2, 3 mol% N2 and 25 ppmv H2S.

This CO2 will be produced with the hydrocarbon gases as the fields are developed. Gas

composition is shown in Table 2.2. Typical values for pressure and temperature are 455 bar

and 161 C at a reservoir datum depth of 4000 m true vertical depth. The temperature and

pressure classification of Gorgon is shown in Figure 2.4.

2.4 Carbon Dioxide storage The total area occupied by the CO2 Injection System outside the Gas Treatment Plant site will

be approximately 6.6 ha. reservoir of carbon dioxide (CO2) will be disposed of by injection

into the Dupuy Formation more than 2000 m below Barrow Island to limit the greenhouse gas

emissions and atmospheric pollutant associated with the Gorgon Gas Development and Jansz

Feed Gas Pipelines production of LNG. The CO2 injection process is described in the Draft

EIS/ERMP (Chevron Australia 2005). The CO2 geology sequestration is shown in Figure 2.5.

These include: [7]

CO2 compression facilities located within the Gas Treatment Plant boundary.

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An above-ground pipeline (approximately 10 km long in an 8 ha basement) between the Gas Treatment Plant and the three to four CO2 injection drill centres to the north.

Approximately eight to nine CO2 injection wells directionally drilled from the three or four CO2 injection drill centres north of the Gas Treatment Plant site.

Observation wells, required to monitor the sub-surface spread of the CO2 plume. Four pressure management water wells, required to manage pressure in the Dupuy formation.

Four pressure management water injection wells for the reinjection of water produced from the lower Dupuy formation by pressure management wells. The water will be reinjected into

the Barrow Group from a vertical depth of 1200 1600 m.

Four shallow drilled anode wells required for each CO2 drill centre for the purposes of cathodic protection. Additional anode wells will be drilled for cathodic protection purposes

for the pressure management wells and the pressure management water injection wells (one

anode well pair per water producer/ injector pair). An anode well will also be required for

each stand alone observation well.

Monitoring activities, including the acquisition of seismic data will be undertaken as part of

ongoing reservoir performance management. Seismic data acquisition is expected to be

repeated a number of times throughout the life of the Gorgon Gas Development, in order to

map the extent of the CO2 plume as it migrates. Differences between the data obtained during

the baseline seismic monitoring and repeat seismic monitoring will be used to map the extent

of the CO2 plume over time.

The terrestrial components of baseline seismic monitoring will use two vibration sources:

subsurface explosives and vibroseis. Approximately 1300 shot holes will be drilled for the

placement of subsurface explosives. These will be drilled at 100 m intervals along lines

spaced 500 m apart. The placement of explosives below the surface karst limestone layer will

be done by drilling the holes to a depth of approximately 15 m below sea level. Purpose-built

drill rigs that have a combination of both sonic and air percussion drilling technology will be

used, reducing the need to use drilling fluids. The charges will be four kg each and double

detonators will be used. Vibroseis will be undertaken in the lower lying, flatter terrain areas

where good ground coupling is attainable and the effect of karst limestone is minimal. The

vibroseis source lines will be spaced approximately 500 m apart, and the vibrator points will

be every 12.5 m along these lines [8].

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3 Gas Processing and LNG Production The Gorgon Gas Treatment Plant is not out of the ordinary. Concerning the gas processing

part the novelty of this project does not rely on the development of new technologies but on

the huge LNG production capacity. It is the first time that such a huge quantity of LNG is

planned to be produced. This project represents a new step in the world gas processing

development.

The Gas Treatment Plant will be located near Town Point (see Figure 3.1) on the east coast of

Barrow Island. The Gas Treatment Plant will produce LNG for international export, domestic

gas for use on the Australian mainland and hydrocarbon condensate (light oil). The block flow

diagram of the plant is quiet classic. This later is shown in Figure 3.2. Note that in order to

reduce the impact on the island (also referring to the QMS), all the components will be pre-

fabricated and assembled off-site into transportable parts. Here it is a description of the main

processing units.

3.1 Inlet Processing The inlet processing facility consists of two slug catchers. These units are designed to

segregate the each different feed gas into three different phases (gas, condensate and water).

The two different feed gases are the Gorgon and the Jansz one. This separation unit provides

steady flow rates to the downstream units. A slug catcher is shown in Figure 3.3.

After separation, the most of the gas is sent to the acid gas removal units while a side stream

of the reduced pressure gas phase of the Jansz slug catcher is sent to the domestic gas

(DomGas) plant to be processed and exported. Gorgon plant will produce 300 terajoules of

domestic gas per day. The DomGas is not going to be explained in this report. Nevertheless it

is important to remember this domestic gas will play a vital role in meeting future energy

needs fro Western Australia. Thus the DomGas plant must have played a very important role

in the project acceptance.

Condensates are sent to stabilization columns. Stabilization consists in stripping lighter

hydrocarbons by using distillation principles. This stabilised condensate stream is then mixed

with the condensates provided by the LNG fractionation train before being stored and

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exported. There are four condensate storage tanks of 35.000 m each. Contrary to the LNG

production, the light-oil production is not out of ordinary. To get a comparison, at Melkoya

platform one tank of 75.000m is used.

The aqueous phase is sent to the Mono-Ethylene Glycol (MEG) unit. This unit consists in

regenerating MEG by removing water and salts in order to reach lean MEG specification. The

MEG loop process is shown in Figure 3.4. MEG is injected in the well-gas in order to prevent

hydrate formation by reducing the water freezing temperature in the pipe. The MEG unit is

designed by Aker Solutions [9].

3.2 Acid gas removal and CO2 compression Carbon dioxide (CO2) and hydrogen sulphide (H2S) need to be removed before the

liquefaction unit for two main reasons. The first one is to meet the LNG product

specifications. And the second one is to prevent acid gas from freezing out in the cryogenic

section. Activated Methyl Di-ethanol Amine (MDEA) technology is used. There are three

Acid Gas Removal Units (AGRUs) in parallel. Each AGRU processes 33% of the feed gas.

Each AGRU consists in one absorber column and a MDEA regenerator system. An AGRU is

shown in Figure 3.5.

One of the main characteristic of the Gorgon project is the environmental concern. That is

why after the AGRU, the acid gas containing around 99.7 mole % of CO2 is compressed and

injected into the subsurface Dupuy Formation. The CO2 injection unit is divided into two

equal parts A and B in order to still provide the injection system in case of shut down of one

part. The AGRU and injection system is shown in Figure 3.6.

3.3 Dehydration and mercury removal Before the liquefaction units, water and mercury also need to be removed. If the gas is not

dried before entering in the cryogenic part, water can freeze out and cause blockages of lines

and equipments. Due to its extreme dryness capacity, a molecular sieve column is used to dry

the gas. Indeed, molecular sieve is much more efficient than glycol unit. It can remove much

more water. Usually glycol units are used in gas processing plants whereas molecular sieves

are used in LNG plant. The reason is that no water is tolerated into the liquefaction part due to

the cryogenic temperatures.

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Remove mercury is to prevent corrosion issues in the heat exchangers. Indeed corrosion

happens if mercury is in contact with aluminium. Mercury adsorbers with non-regenerable

packed beds and adsorbers after filters are used to ensure a good removal of mercury [9].

3.4 Liquefaction process The liquefaction process is the Air Products and Chemicals Incorporated (APCI) Split-MR

Propane Pre-Cooled Mixed Refrigerant (MR) Process. This APCI 5MTPA refrigeration cycle

is shown in Figure 3.7 (Chevron Australia, September 2009). A simplified sketch of the

liquefaction process is shown in Figure 3.8 [10]. This process is not a new discovery. In fact

most of the worlds LNG is produced by using the C3MR process.

Before entering in the main cryogenic heat exchanger (MCHE), the pre-treated gas needs to

be cooled down in order to remove the heavier hydrocarbons that can freeze out due to the

very low temperature. For this purpose, propane refrigerant is used to pre-cool the gas. This

pre-cooled gas is then fed into the scrub column which separates the gas from the

condensates. The heavier hydrocarbons and aromatics are sent to the fractionation unit. This

propane pre-cooling part is also used to pre-cool the mixed refrigerant which will provide the

liquefaction energy. The medium used to cool down the propane is ambient air. It can be

wondered why ambient air was chosen as cooler instead of sea water. One answer can be that

the low cost investment and the easy availability of air-cooling came first. Even if air cooler is

bigger and lower efficient than water cooler it is still the most used in LNG plants.

To provide enough energy, each liquefaction train has refrigeration compressors driven by

Frame 7 gas turbines. This gas turbine is ideal for plants that require high efficiency and

shaft speed for direct coupling to the generator[11].

3.5 Fractionation The fractionation unit consists in a succession of distillations in order to recover ethane and

propane from the gas allowing sufficient refrigerant make up to be produced in the

fractionation unit. The condensates are sent to condensate storage tanks.

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3.6 End flash, nitrogen rejection The liquefied natural gas is sub-cooled after the MCHE and flashed off in the nitrogen

rejection column. This end flash has two main uses. The first one is to remove Nitrogen and

some Methane in order to meet the LNG specifications and specifically the required heating

value. The second one is to provide enough fuel gas to run the gas turbines.

3.7 Power and thermal facilities The main ancillary system is the power generation provided by five Frame 9 gas turbines

generators. With all five gas turbines running the maximum power output of the power

generation plant is 550 MW. This plant is used to generate power for electrical consumers in

the gas treatment plant, the administration area, etc. The estimated total electrical power

required is 416 MW [9]. Therefore, the Gorgon project uses the N+1 operating philosophy,

one gas turbine more than required.

At the liquefaction plant, everything is done to optimize the energy and the thermal heat

recovery. There is a Waste Heat Recovery Unit (WHRU) in order to recover the heat

available from the gas turbine exhausts. This recovered heat is then sent to lots of heat

consumers in the gas treatment plant, including inlet gas heating, AGRU reboilers, MEG

regeneration, etc. A fuel gas recycle system is also used to provide fuel gas throughout the gas

treatment plant. This fuel gas is provided by three parts of the plant: the dehydration and

mercury removal unit, the end flash unit and by the BOG from the LNG storage tanks.

3.8 LNG storage and loading The LNG storage and loading challenge is to provide a continuous production of LNG. There

are two full containment LNG tanks with a capacity of 180 000 m each. It is the CB&I

company that has been awarded a contract by Chevron Australia for the LNG and condensates

tanks [9]. The LNG loading takes place at the jetty which is approximately 4 km offshore

from the gas treatment plant at Town Point. The jetty has two LNG carriers berths, each

equipped with four loading arms. There are two liquid arms, one hybrid (liquid-vapour) arm

and the last one is used to return the Boil off gas (BOG). A BOG flare is provided for safety

purposes.

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4 Environmental concerns

4.1 Environmental Significance of Barrow Island Barrow Island was set aside as a nature reserve in 1910 in recognition of its outstanding flora

and fauna values. It is currently reserved as a Class A Nature Reserve for the purpose of

Conservation of Flora and Fauna, which represents the highest level of protection afforded

under State legislation. In 2004, the majority of the waters around the island were included in

the Barrow Island Marine Park and Barrow Island Marine Management Area (note that the

Barrow Island port area was excluded). The island nature reserve is vested in the

Conservation Commission and the marine reserves in the Marine Parks and Reserves

Authority. Both are managed by the Department of Environment and Conservation (DEC).

The biodiversity values of Barrow Island are unique and significant on an international scale.

It is Western Australias second largest island at approximately 23,600 hectares, and one of

the largest land masses in the world without any established introduced vertebrates.

Thousands of years of isolation have resulted in the genetic differentiation of species from

mainland populations. In addition to reptiles and invertebrates, Barrow Island is also a

significant nesting site for marine green and flatback turtles.

Such an important environment and biodiversity need to be protected during the development

of such a huge gas plant. In order to manage it, the Gorgon Project has established three

independent Expert Panels. The objective of these Expert Panels is to follow the execution of

the project by providing advice to the Proponent (Chevron Australia Pty Ltd) and the

Minister. Each panel will provide advice, relevant to their subject matter, on management and

monitoring, including implementation of special plans, in accordance with State and

Commonwealth [12].

4.2 Quarantine Expert Panel The Gorgon Project on Barrow Island will pose new quarantine challenges to the conservation

values of the island. Activities associated with the project will increase the volume of cargoes

and number of personnel movements compared to historical or current oilfield operations on

the island. These numbers would be particularly pronounced during the construction phase,

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and would remain at higher than current levels during the operational phase. The higher

number of personnel and cargo movements to Barrow Island therefore presents a substantial

increase in the potential for non-indigenous organisms to be transported to the island.

To protect Barrow Island from potential introductions of non-indigenous species, the Gorgon

Joint Venturers have developed a new approach to quarantine by developing a risk-based

Quarantine Management System. As there is no precedent for a quarantine program of such

rigor anywhere else in the world, the Joint Venturers have been guided by the specific advice

of the EPA (Environment Protection Authority) to develop quarantine protection for Barrow

Island, according with Protection and Biodiversity Conservation Act 1999 [13]. As a

consequence of this advice, the Joint Venturers established a Quarantine Expert Panel,

initiated an extensive and transparent process of community consultation, and in concert with

the community and experts, developed of a set of standards for acceptable. The Quarantine

expert panel advices include:

Development and implementation of marine and terrestrial Quarantine Management System (QMS); the panel decides also about improvement of its effectiveness;

Preventing the introduction of non-indigenous terrestrial species and marine pets to Barrows island through all proposal attributable introduction pathways;

Detecting the presence of non-indigenous terrestrial species and marine pets and detecting environmental change caused by the presence of them;

Control and eradication measures in the event that a non indigenous species is detected; Review and recommend quarantine studies [12]

4.3 Construction Dredging Environmental Expert Panel The role of this panel is to provide advice to the proponent and the minister on construction

dredging a spoil disposal management and monitoring. It is also required to evaluate costal

and marine state and the environmental impact even before and after project development

[12].

4.4 Marine Turtle Expert Panel This panel must build understanding of the turtle population in order to better predict, monitor

and manage potential impacts associated with the construction and operation of the Gorgons

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gas field [12]. The important of this panel lies in the relevance of Gorgon as a nesting area.

Over 3000 individuals of flatback turtles have now been recoreded nesting on the eastern

beach of Borrow Island [14].

4.5 Environmental Approval The environmental approvals have imposed very stringent environmental conditions on the

GJV, including the requirement to comply with over 20 environmental management plans. In

addition to the requirements of the environmental approvals, the GJV has committed to

conservation initiatives and undertakings worth approximately $150 millions. It could be read

as a further way the GJV uses in order to reduce the footprint of the project. These initiatives

include:

the Northwest Shelf Flatback Turtle Conservation Program, valued at $62.5 million over the life of the project (expected to be 60 years) to increase protection of the turtles in areas away

from Barrow Island;

the Northwest Shelf Flatback Turtle Intervention Program, capped at $5 million, to improve recruitment to the turtle population in the event that monitoring demonstrates an impact upon

the turtles;

the Threatened Species Translocation and Reintroduction Program, valued at $10 million over 12 years, for selected species from Barrow Island to other suitable locations around the

State;

monitoring and auditing of marine activities during the projects dredging and marine construction phase, up to $2.5 million;

a financial guarantee, capped at $10 million, to cover Government costs for the eradication of viable non-indigenous species introduced to Barrow Island; and

$60 million for Net Conservation Benefits (under the Gorgon State Agreement). The GJV is also required to fund the Department of Environment and Conservation to

maintain a permanent management presence on Barrow Island to manage the impacts, if any,

on the islands marine conservation over the life of the project [14].

4.6 Atmospheric Emissions The main points considered in (EIS/ERMP) [15] are atmospheric emissions. Again GJV is

developing efficient technologies to decrease emissions to a very low level for such an

15

enormous plant. Predicted emissions, which would occur during the construction,

commissioning, operation, maintenance and decommissioning phases of the proposed Gorgon

development are based on current information, and opportunities to reduce the levels will be

pursued. The air emissions include: 4.0 million tones of CO2 equivalents of greenhouse gases

(with CO2 injection) per annum, 4430 tonnes of NOx per annum, 0.15 tonnes of SOx per

annum and 241 tonnes of particulates (PM10) per annum [16].

The JV partners have adopted the Gorgon Gas Development Greenhouse Gas Management

Strategy to responsibly manage greenhouse gas emissions. The integration of this strategy into

the gas processing facility design resulted in about 45 million tonnes less global greenhouse

emissions per year, compared to the use of coal. The development concept also results in only

40 percent of the greenhouse gas emissions per tonne of LNG produced than that of the

original 1998 concept that formed the basis of Greenhouse Challenge Agreement with the

Australian Greenhouse Office (see Figure 4.1). The emissions reduction is achieved by

several ways. The first way is the replacement of the offshore gas processing platform with an

all sub-sea development. Then, the LNG process technology and the waste heat recovery are

optimized: Were also committed to an energy optimization process to improve plant

efficiency and minimize energy consumption thus lowering greenhouse gas emissions [12].

Finally, the injection and subsurface storage of Carbon Dioxide significantly reduce

greenhouse gas emissions.

In order to achieve potential greenhouse gas reductions, other opportunities were undertaken,

including investing in commercial forestry, assisting in revegetation or land rehabilitation

plantings, facilitating reduced land clearing, undertaking the disposal of reservoir CO2 by

injection into the subsurface, assisting other industries to switch to alternative fuels (e.g. from

coal to gas), facilitating the use of compressed natural gas (CNG) as vehicle fuel, providing

support for renewable energy technologies, promoting the sale of CO2 as a feed stock to

another company or industry and market-based options [16].

16

5 Gorgon Project Economy Gorgon will be an important pillar of the Australian economy for more than 40 years. The

economic benefits resulting from the proposed Gorgon Development will have national, state

and regional dimensions. Studies already carried out indicate that Western Australias

economy is expected to benefit from the Gorgon Project by approximately $4 billion [2].

There will also be improvements to business investments and Gross State Product (GSP)

leading to flow-on benefits for business, employment and government revenues. In particular

an increase in Australian Gross Domestic Product (GDP) of approximately $3.6 billion by

2030 should be reached (see Figure 5.1) [2].

Also the domestic supply (a minimum 15% of gas production) will provide positive effects

mainly to Western Australia economy. In fact the access to secure and affordable energy,

particularly natural gas, will underpin the States mining and resource processing industries,

will fuel power generation and will supply small businesses and households. Western

Australia is the most energy and gas-dependent economy in Australia. Natural gas supplies

half of the States primary energy requirements and fuels 60% of the States electricity

generation. Given the dependence on gas-fired electricity, the availability and affordability of

natural gas will have a major direct impact on households and small businesses through

electricity prices, as well as gas prices [17].

5.1 Economic growth - National and local benefits The main economic benefits, which Gorgon project will provide to Australia and Western

Australia, will derive from the combination of:

export income tax paid by the Joint Venturers businesses and individuals employed the amount of money spent in the local economy

The location of the gas-fields and close infrastructures coupled with estimates showing they

contain about 40Tcf of gas means Australia will be in a prime position to meet future

17

market demands. Thereby an increase of exports in excess of $2 billion per year is expected

during operation [2].

Another key benefit will come from the taxation system. It will guarantee approximately $17

billion in revenue from company tax and Petroleum Resources Rent Tax (PRRT) [2]. PRRT is

a Commonwealth tax and only applies to areas under Commonwealth sovereignty the

offshore. It is levied at 40% of profit after taking into account assessable receipts and

deductible expenditures.

Gorgon investment in Australia is generating more and more jobs and supplier opportunities

as local companies get involved with the project. In addition to a range of career opportunities

with Chevron, the project will also result in employment opportunities with Gorgon

contractors. Peak construction period will provide employment in Western Australia of

around 10000 direct and indirect jobs. Globally the Gorgon Project is predicted to generate

and sustain over 6000 jobs on average through the decades of operation, with 1700 generated

in Western Australia (see in Figure 5.2) [2].

Western Australia and the Pilbara region will benefit from increased demand for goods and

services that will further stimulate business development. The project is expected to spend

about $20 billion on Australian goods and services over the next 4 to 5 years. And early

indications are confirming that Gorgon will spend $33 billion on local goods and services in

the first 30 years [12].

5.2 Innovative Marketing Approach Historically the Asia-Pacific LNG market has involved project owners selling their product in

a coordinated manner. The Gorgon Joint Venturers however have adopted an equity

marketing model where each owner sells its share of the LNG produced separately. This is a

first for a significant size project in the region. Equity marketing has lead to greater flexibility

in the offerings that can be made to customers. It also assures more freedom for the owners to

pursue the markets that meet their requirements. On the other hand some critics fear that joint

selling of Gorgon gas will result eventually in less competition not more and can only lead to

higher energy prices for Australian consumers.

18

The strength of the three Gorgon Joint Venturers has been critical to the success of this

innovative approach - between them they are involved in eight other LNG projects that are

operating or currently under construction [2]. The Gorgon Joint Venture consists of Australian

subsidiaries of three international energy companies:

Chevron Australia (a subsidiary of Chevron) (47% share and project operator) Shell Development Australia (a subsidiary of Royal Dutch Shell) (25%) Mobil Australia Resources (a subsidiary of Exxon Mobil) (25%) Osaka Gas (1.25%) Tokyo Gas (1%) Chubu Electric Power (0.417%)

The Gorgon joint venture participants are aggressively pursuing a number of market

opportunities in key customer countries. This approach has delivered real benefits to the

project.

5.3 Downstream contracts Chevron Australia has executed Sale and Purchase Agreements (SPAs) with Osaka Gas

(1.375Mtpa for 25 years and 1.25 percent equity in the Gorgon Project), Tokyo Gas (1.1Mtpa

for 25 years and 1 percent equity), Chubu Electric Power (1.44Mtpa for 25 years and 0.417

percent equity in the Gorgon Project) and GS Caltex of South Korea (0.5Mtpa for 20 years

from Gorgon and Chevron system gas). Chevron Australia also has Heads of Agreements

with Korea Gas Corporation KOGAS) (1.5Mtpa for 15 years); Nippon Oil Corporation (0.3

Mtpa for 15 years) and Kyushu Electric (0.3 Mtpa for 15 years) [12].

Shell has entered into long-term LNG sale and purchase agreements with PetroChina

International Company Limited and BP Singapore Pte. Limited and also has secured capacity

at LNG receiving terminals including the terminals at Energia Costa Azul in Baja California,

Mexico and Hazira in Gujarat, India [12].

An Australian subsidiary of ExxonMobil has signed long-term sales and purchase agreements

with Petronet LNG Limited of India and PetroChina International Company Limited for the

supply of LNG from the Gorgon Project. The agreement with Petronet LNG is for the supply

of approximately 1.5 Mtpa of LNG over a 20-year term while the agreement with PetroChina

is for the supply of approximately 2.25 Mtpa over a 20-year term. Together, these two sales

19

and purchase agreements commit the ExxonMobil subsidiary's share of LNG from the 15

Mtpa Gorgon LNG Project [12].

Further gas sales in the Asia-Pacific region are expected as participants leverage their

international positions in LNG infrastructure and gas markets.

5.4 The Gas Market Australia opportunities Rapid population growth, urbanization and industrialization added to declining supplies of

domestic crude oil, are fueling demand from industrial and utility customers for large volumes

of LNG and long-term contracts. In this background Australia has the possibility to assume a

leading role as producer of gas in the Asia Pacific Region. There are lots of factors which

contribute to the likelihood of this scenario:

Vast and growing reserves of natural gas

Access to expanding energy-hungry markets

A world demanding cleaner energy

The experience and skill in the development and execution of large resource projects

Therefore the opportunities presented by the Gorgon Project ensure that Australia will be well

positioned to secure a significant share of the growing global LNG market. One more key

factor is that Australia offers a stable investment environment and significantly reducing

investment risk for a long-term international LNG export development. In Australia, LNG

projects receive strong support from Government at all levels [2].

The Gorgon Project will also help underpin the development of new technologies and skills,

for example in disposal of CO2 by injection and subsea technology. Thus additional capacity

for future regional growth will be created and Australia could be a forerunner in these

innovative fields. Moreover the Gorgon Project could lead to further development of other

regional gas resources identified in the area, extending and expanding the benefits of the

initial development [2].

20

Conclusions: From the analysis proposed in this paper we can draw some simple conclusions:

The estimated 40Tcf of gas, contained in the Gorgon field, will assure a long and affordable supply of natural gas. This will lead Australia to play an important role in

the energy market, most of all in the Asia Pacific region.

The project will provide immediate economic benefits. A substantial AU$64 billion net will boost Australias Gross Domestic Product. Peak construction employment in

WA of around 10000 direct and indirect jobs. Anticipated State and Federal

Government revenue of about AU$40 billion.

The proposed project has attracted criticism from conservation groups in relation to the potential impact upon Barrow Island's ecology. The island is a Class A nature

reserve. Taking account of that, a set of rigorous environmental conditions for the

construction and operation of the Gorgon Gas Development has been planned. The

goal is to demonstrate that conservation and development can successfully co-exist.

Gorgon project proposes also an advanced system to minimize atmospheric emissions. The proposed LNG facility on Barrow Island has the potential to be among the most

greenhouse gas efficient of its kind in the world. Very significant in this sense is the

carbon dioxide injection technology. Gorgon will be one of the first projects to

implement the CO2 storage underground system in such a large scale. The results

reached will be meaningful in order to evaluate the feasibility of this technology. A

positive outcome could foster other similar projects.

21

References [1] Chevron, 2nd September 2009, Gorgon Gas Development and Jansz Feed Gas Pipeline Terrestrial and Marine Quarantine Management System, Paragraph 2.1.4.

[2] Chevron, Gorgon Project Overview of Gorgon Subsea Well Design and Construction

[3] Teobald Neil, 23rd World Gas Conference, Amsterdam 200. The Worlds Most

Significant Gas Fields

[4] Offshore Petroleum Exploration Acreage Release, Regional Geology of the Northern

Carnarvon Basin 2010

[5] Brian Fleay, Western Australia Gas Supply Revision 6 - October 2009

[6] Offshore-technology.com. SPG Media Limited, Gorgon, Northern Carnarvon Basin"

[7] Chevron, 2nd September 2009, Gorgon Gas Development and Jansz Feed Gas Pipeline

Terrestrial and Marine Quarantine Management System, Paragraph 2.1.3

[8] Chevron, 2nd September 2009, Gorgon Gas Development and Jansz Feed Gas Pipeline

Terrestrial and Marine Quarantine Management System, Paragraph 2.1.5

[9] Chevron Australia, Gorgon Gas Development and Jansz Feed Gas Pipeline - September

2009

[10] Dr. Mark Pillarella, Dr. Yu-Nan Liu, Joseph Petrowski, Ronald Bower, Air Products and

Chemicals, The C3MR Liquefaction cycle: versatility for a fast growing, ever changing LNG

industry unknown

[11] GE Energy, Liquefied Natural Gas Enhanced solutions for LNG Plants unknown

[12] Chevron Australia, www.chevronaustralia.com

22

[13] Neil Theobald, Innovative supply solutions to the Asia Pacific Gorgon project

2006

[14] Government of Western Australia, department of State Development,

www.dsd.wa.gov.au

[15] The Environmental Impact Statement/Environmental Review and Management Program

for the Proposed Gorgon Development

[16] The national newsletter of petroleum exploration society, www.pesa.com.au

[17] DomGas Alliance, Gorgon Gas Project: Application for Joint Selling Authorization 2009

[18] Chevron Australia, Subsurface development of CO2 disposal for the Gorgon Project -

2009

23

Bibliography Department of Resources, Energy and Tourism, "Offshore Acreage Release 2008: Exploration

History".

Chevron Australia, "Gorgon EIS 2009-Response to Submissions"

Chevron Australia, Project Overview - 2009

DomGas Alliance, GORGON GAS DEVELOPMENT: EPA REPORT 1323 2009

DomGas Alliance, Gorgon Gas Project: Application for Joint Selling Authorization 2009

Websites: International Gas Union, www.igu.org

SubseaIQ, Offshore Field Development, www.subseaiq.com/data

Department of State Development, Australia, www.dsd.wa.gov.au

Domgas Alliance, www.domgas.com.au

Chevron, www.chevron.com

ExxonMobil, www.exxonmobil.com

RoyalDutch Shell, www.shell.com

Chevron, Gorgon, Its time is now -

http://www.chevronaustralia.com/ourbusinesses/gorgon.aspx

24

Tables Table 2.1 - Greater Gorgon fields reserves, Chevron, 2nd September 2009, Gorgon Gas Development and Jansz Feed Gas Pipeline Terrestrial and Marine Quarantine Management System

Table 2.2 - Key elements of the Proposed Gorgon Development, Final Environmental Impact Statement. Australia Government, Environmental Protection Authority.

25

Figures Figure 1.1 - Main structures of Gorgon plant, Gorgon project Overview of Gorgon Subsea Well Design and Construction

26

Figure 1.2 - Subsea equipments,The Worlds Most Significant Gas Fields: Gorgon Field. Niel Theobald, Chevron Australia, June 2006

27

Figure 2.1 - Structural elements of the Northern Carnarvon Basin and adjacent basins, oil and gas accumulations and selected wells, Release Areas W09-12, W09-13, W09-14, W09-15, W09-16, W09-17, W09-18 and W09-19 Dampier Sub Basin, Western Australia. Australian Government, Department of Resources, Energy and Tourism.

28

Figure 2.2 The Greater Gorgon Project fields, Neil Theobald, Innovative supply solutions to the Asia Pacific Gorgon project 2006

29

Figure 2.3 - Geography of Gorgon Field and Barrow Island, Chevron, 2nd September 2009, Gorgon Gas Development and Jansz Feed Gas Pipeline Terrestrial and Marine Quarantine Management System

30

Figure 2.4 Gorgon classification, Statoil, Kristin Petek, November 2010

Figure 2.5 - Geo-sequestration of CO2, The Worlds Most Significant Gas Fields : Gorgon Field. Niel Theobald, Chevron Australia, June 2006

31

Figure 3.1 - Location of the gas treatment plant in the Barrow Island, Chevron, 2nd September 2009, Gorgon Gas Development and Jansz Feed Gas Pipeline Terrestrial and Marine Quarantine Management System.

32

Figure 3.2 Gas Treatment Plant Block Flow Diagram, Chevron Australia, Gorgon Gas

Development and Jansz Feed Gas Pipeline - September 2009

33

Figure 3.3 Slug Catcher

Figure 3.4 MEG regeneration loop

34

Figure 3.5 Acid Gas Removal Unit (AGRU)

Figure 3.6 Acid Gas Removal and CO2 Injection System Block Flow Diagram, Chevron Australia, Gorgon Gas Development and Jansz Feed Gas Pipeline - September 2009

35

Figure 3.7 APCI 5 MTPA Refrigeration Cycle, Chevron Australia, Gorgon Gas Development and Jansz Feed Gas Pipeline - September 2009 Figure 3.8 C3MR Process, Dr. Mark Pillarella, Dr. Yu-Nan Liu, Joseph Petrowski, Ronald Bower, Air Products and Chemicals, The C3MR Liquefaction cycle: versatility for a fast growing, ever changing LNG industry

36

Figure 4.1 Greenhouse Gas Emissions Efficiency Improvements, Greenhouse Gas Management, Chevron Australia LTD. Figure 5.1 National Gross Domestic Product and WA Gross State Product, The Worlds Most Significant Gas Fields: Gorgon Field. Niel Theobald, Chevron Australia, June 2006

37

Figure 5.2 Employment trend, The Worlds Most Significant Gas Fields: Gorgon Field. Niel Theobald, Chevron Australia, June 2006

38

Appendices Appendix 1 Gorgon Subsea Development [1]

39

Appendix 2 Geology of DUPUY formation and CO2 Storage [18] CO2 will be separated from the hydrocarbon gases at the proposed LNG processing facility to

be built on Barrow Island. Established global practice is for this reservoir CO2 to be vented to

the atmosphere; however the Gorgon Joint Venturers plan to dispose of this reservoir carbon

dioxide by injecting it underground into the Dupuy Formation beneath Barrow Island. General

sketch of the purpose is shown in figure 1. Subsurface evaluation of the Dupuy Formation

for CO2 disposal has focused on reservoir characterization and narrowing subsurface

uncertainty ranges.

The Gorgon Project has overcome several technical challenges during the concept selection

phase of development: one of the longest sub-sea tie-backs in the world (145kms) in water

depths greater than 1km and challenging seafloor terrain with the pipeline crossing the

continental shelf; Barrow Island is a remote location and a Class A Nature Reserve; the

nearest major logistical staging point (Perth, Australia) is over 1200km away from Barrow

Island; strict quarantine management regime in place to prevent non-indigenous species

contact; and finally, the Gorgon gas field has approximately 14% CO2 in the reservoir fluid

composition which represents a significant volume of CO2 (of the order of 2 Tscf ). CO2

present in the produced reservoir fluids from the Greater Gorgon Area Fields must be

removed from the raw gas stream prior to the liquefaction process of LNG manufacture due to

CO2 becoming solid under process conditions. CO2 will be removed before liquefaction via an

amine contact process and a large volume of CO2 will be produced at high pressure.

The Dupuy Formation is located more than 2 km below Barrow Island. The disposal of

Gorgon Project reservoir CO2 is a significant commitment by the Joint Venture participants

due to the size of the Greater Gorgon Area Fields and overall volume of CO2 it contains. Over

the duration of the Gorgon Project it is expected that more than 2 Tscf or ~ 120 million tonnes

of CO2 will be injected in the Dupuy Formation.

Processing of the Gorgon Project gas will occur on Barrow Island, with the associated CO2

being disposed beneath Barrow Island into the Dupuy Formation. The Dupuy Formation is

Late-Jurassic aged and consists of sandstones and siltstones, with overall thickness of between

200m and 500m. Barrow Island itself is the surface expression of the dominant anticlinal

40

feature of the Barrow Sub-basin of the offshore Carnarvon Basin, off the Northwest coast of

Western Australia.

The Dupuy Formation is a regionally extensive clastic formation, thought to have been deposited in a deep water slope depositional setting. This unstable sandy slope was dominated by gravity processes with sediment interpreted to have been sourced from a number of influx points at the edge of a large hinterland to the east. The Dupuy Formation, which lies at a depth of more than 2000mSS, has been divided into four major rock units; the Basal Dupuy, the Lower Dupuy, the Upper Massive Sand, and the Upper Dupuy. These units are shown in figure 2.

The lowermost unit, the Basal Dupuy, is a sideritic cemented, fine to medium grained

sandstone, with generally poor reservoir quality. The Basal Dupuy is not an injection target.

The Lower Dupuy, which is the lower injection target, is a fine grained sandstone and

siltstone. It is mostly sandstone (up to 90% sandstone) in the northern portion of Barrow

Island and is shaley siltstone in wells to the south. The Upper Massive Sand is the upper

injection target and is a fine to medium grained, blocky sandstone, capped by a fining upward

unit at the top. The Upper Massive Sand, which is thought to be a slope deposit, contains

important intra-reservoir siltstone baffles, such as the Perforans Shale (actually a very low

permeability siltstone). The Upper Dupuy is a bioturbated siltstone with minor interbedded

sandstone lenses. It forms a barrier/baffle at the top the Dupuy Formation, and is not an

injection target. The Upper Dupuy is thought to have been deposited in a shelfal/offshore

transition environment.

Immediately above the Dupuy Formation is the Basal Barrow Group Shale, which is a deltaic

shale unit at the base of the Barrow Delta. It is present in every well which penetrates down to

the top of the Dupuy Formation on Barrow Island, and is therefore considered to be a

regionally extensive and continuous barrier. The stratigraphy of Barrow Island is shown in

figure 3.

The Jurassic Dupuy Formation is the CO2 injection target. Beneath Barrow Island, the Dupuy

Formation is folded into an open anticline. It is planned that CO2 will be injected into the

Lower Dupuy and lower part of the Upper Massive Sand (below the Perforans Siltstone;

Figure 5). During injection, the laterally discontinuous siltstones in the Upper Massive Sand

(both above and below the Perforans Siltstone) and the Perforans Siltstone are expected to

impede the vertical migration of the injected CO2. If vertically migrating CO2 reaches the top

41

of the Upper Massive Sand, the upwards migration of the CO2 will be further slowed by fine-

grained beds in the Upper Dupuy. Migrating CO2 will then encounter the Basal Barrow Group

Shale, which is expected to form an effective barrier to CO2 movement from the Dupuy

reservoir into the Lower Barrow Group.

Figure 1 - CO2 separation and sequestration general draft, Executive Summary from Gorgon Due Diligence, Government of Westren Australia, Department of Mines and Petroleum .

Figure 2 - DUPUY formation, Executive Summary from Gorgon Due Diligence, Government of Westren Australia, Department of Mines and Petroleum .

42

Figure 2 - Stratigraphy of Barrow Island, Executive Summary from Gorgon Due Diligence, Government of Westren Australia, Department of Mines and Petroleum .