Why does Australia have so much Natural Gas?

Gorgon Project, Chevron.com

Chevron is a multinational corporation with offices, plants, pipelines, partnerships, and subsidiaries located all over the world. One of the company’s largest and most important overseas projects is the Gorgon Project – and associated smaller projects – situated off the coast of Western Australia.

Australia does not produce a lot of oil, but it produces an abundance of natural gas. This phenomenon is due to the geology of the Australian continent (Blewett, 2012, p. 221).

The Northern Carnarvon Basin, created during the Paleozoic period, is located off the northwestern coast of Australia, on the northwest shelf. “The basin is Australia’s premier hydrocarbon province where the majority of deep water wells have been drilled (greater than 500 meters water depth) . . . Almost all the hydrocarbon resources are reservoired within the Upper Triassic, Jurassic, and Lower Cretaceous sandstones beneath the regional early Cretaceous seal” (Geoscience Australia, 2020). The faults on this area run north or northeast, among “structural highs and sub-basins” (Geoscience Australia, 2020) which occurred over four geological phases involving glacial and tectonic activity (Geoscience Australia, 2020).

The basin covers 535,000 square kilometers, with water depths up to 4,500 meters. Paleozoic, Mesozoic, and Cenozoic sediment covers the area, up to 15,000 meters thick. The area comprises two Mesozoic petroleum supersystems (Geoscience Australia, 2020).

Total petroleum systems of the northwest shelf include the Dingo-Mungaroo/Barrow system and the Locker/Mungaroo/Barrow system. In the Dingo-Mungaroo/Barrow system, the hydrocarbon source rock is composed of Jurassic Dingo Claystone. The reservoir rocks comprise the Triassic Mungaroo Formation, Jurassic rocks, and the Cretaceous Barrow Group. In the Locker/Mungaroo/Barrow system, the source rock is composed of Triassic Locker Shale. The reservoir rocks comprise the Triassic Mungaroo Formation and the Cretaceous Barrow Group. Muderong Shale makes up the vast seal over much of the area (Bishop, 1999, p.6-7).

A total petroleum system is composed of several elements: the depocenter, which is the basin; the source, which is made of rocks containing organic materials; the reservoir, which is made of porous, permeable rock, such as sandstone; the seal, which is made of impermeable rock, such as shale; the trap, which holds the accumulation of source rocks; the overburden, which is composed of sediments subjected to heat; and the migration pathways, which allow the source rocks to form a link with the trap (Blewett, 2012, p. 176).

Additionally, there must be geochemical processes which cause “trap formation, hydrocarbon generation, expulsion, migration, accumulation, and preservation” in a precise order with exact timing (Blewett, 2012, p. 176). Millions of years of geological events, such as the shifting of tectonic plates and glacier movement, as well as extreme changes in weather, such as the change from the Ice Age to a more temperate climate, formed the particular geology which makes up the Australian continent and its surrounding oceans (Blewett, 2012, p. 217).

“The main trap styles in the [Carnarvon] basin are anticlines, horsts, fault roll-over structures, and stratigraphic pinch-outs beneath the regional seal” (Blewett, 2012, p. 220). Australia has an abundance of natural gas due to the type of vegetation which decayed and became trapped in “non-marine coaly source rocks” (Blewett, 2012, p. 221) and the fact that some basins did not evolve long enough to create the conditions to produce oil.

Chevron entered the Western Australia oil and gas market when it purchased Caltex in 1952. In 1980, the Gorgon natural gas field was discovered west of Barrow Island; and in 2003, Chevron received permission from the Western Australia government to build a natural gas plant on Barrow Island (Chevron Australia, 2020).

Barrow Island is located 60 kilometers off the northwest coast of Western Australia. Chevron’s Gorgon Project includes three liquefied natural gas (LNG) processing plants capable of producing 15.6 million tonnes per annum (MTPA), and a domestic natural gas plant capable of producing 300 terajoules of natural gas per day (Chevron Australia, 2020). According to the operators of the Dampier-Bunbury Pipeline, which transmits this natural gas to distributors, one terajoule of natural gas can provide energy to the average household in Western Australia for 50 years, so Chevron’s Gorgon Project is a significant contribution to Western Australia’s regional economy (Dampier Bunbury Pipeline, 2020). The project is expected to be productive for 40 or more years (Chevron Australia, 2020).

The onshore Gorgon Project also includes three acid gas removal units, two LNG tanks, four condensate tanks, three CO2 compression plants, two monoethylene glycol (MEG) processing plants, 2 inlet processing units, and ground flare capabilities. Marine facilities, an airport, employee housing, a fire station, laboratory, warehouse, workshop, and a permanent operations facility complete the physical structure of the Barrows Island onshore project (Chevron Australia, 2020).

“A subsea gas gathering system is located on the ocean floor at the Gorgon and Jansz-Io fields, located about 65 and 130 kilometers respectively off the west coast of Barrow Island” (Chevron Australia, 2020). From there, natural gas from both fields is transmitted to the Barrow Island facility by undersea pipelines. After processing, gas for domestic use is transmitted through a 90 kilometer domestic gas pipeline that ties in to the Dampier-Bunbury Natural Gas Pipeline. Once the LNG is processed, it is stored and shipped by large LNG tankers to Japan and other Asian countries (Chevron Australia, 2020).

The Dampier-Bunbury Pipeline (DBP), at 1600 kilometers long, is the longest pipeline in Australia. Built in 1984, it is expected to last for another 50 years. Every year, it receives 112,000 hours of planned maintenance to ensure its safety and optimal condition. Twenty-seven turbine compressor units, located at ten sites along the pipeline, exert enough pressure to push the natural gas along the pipeline. It has functioned at 99% efficiency for the last ten years. Owned by the Australian Gas Infrastructure Group, more than 2 million homes and businesses benefit from the pipeline. The company also supplies natural gas to power generators, mines, and manufacturers — and other companies can tie in to the pipeline (Dampier Bunbury Pipeline, 2020).

DBP owns 34,000 kilometers of distribution networks, 5,500 kilometers of transmission pipelines, 52 petrajoules of storage capacity, employs 315 workers, and contracts with 1,600 contractors. The company’s goal is to provide natural gas at the lowest possible cost. The company provides 21% natural gas for power generation; 39% for mineral processing; 9% for other industrial purposes; 9% for retail outlets; 22% for mining.  Alcoa and BHP Billiton are two of its large industrial customers. The company provides natural gas to Synergy and Alinta for power generation (Dampier Bunbury Pipeline, 2020).

DBP operates the Dampier-Bunbury Pipeline for the Australian Gas Infrastructure Group (AGIG). It also plans and constructs metering stations, executes the tie-ins for other companies, and provides an odorization service. In 2013, “DBP completed the metering station for the connection of the Chevron-operated Gorgon Project” (Dampier Bunbury Pipeline, 2020).

Transmission pipelines are usually 6-48 inches in diameter and can handle pressures of 200-1500 psi. The high pressures move the natural gas through the line. Distribution pipelines are separated into main lines and service lines and carry natural gas to homes and businesses. They operate at lower pressures for safety reasons (Pipeline Safety Trust, 2019).

Compressors fueled by electric or natural gas use high pressure to push the gas through the pipeline. Compressor stations are located about every 50 to 100 miles along the line, and pressures can be adjusted as needed (Pipeline Safety Trust, 2019).

Gas pipeline operators, such as DBP in Western Australia, monitor the pipeline for problems using “a Supervisory Control and Data Acquisition system (SCADA). A SCADA is a pipeline computer system designed to gather information such as flow rate through the pipeline, operational status, pressure, and temperature readings” (Pipeline Safety Trust, 2019). These readings help operators to address problems quickly and easily. Operators, for example, can isolate a section of pipe that is malfunctioning or adjust flow rates via the compressors and valves (Pipeline Safety Trust, 2019).

When a transmission line reaches the utility company’s “city gate,” it begins to transmit gas into the lower pressure distribution system that ultimately delivers the gas to homes and businesses. This is where the odorant is added to the gas. Gas mains, which are usually 2-24 inches in diameter, utilize pressures up to 200 psi. The service lines, on the other hand, only use pressures up to 10 psi (Pipeline Safety Trust, 2019).

The gas utility company is responsible for monitoring flow rates and pressures along the distribution line. When regulators sense a change in pressure, they will open or close in order to adjust the amount of pressure in the line. Relief valves release excess gas if the pressures build too high (Pipeline Safety Trust, 2019).

Pipeline operators, such as DBP in Western Australia, must monitor pipes for corrosion, leaks, breakages, and construction workers digging too close to the lines. They must follow pressure specifications determined by government regulatory bodies, otherwise, pipelines can become a safety and environmental hazard to the local community (Pipeline Safety Trust, 2019).

Barrow Island is a Class-A nature reserve, and Chevron has worked hard with the Western Australia government to maintain the local habitat for the native flora and fauna. Their goal to reduce CO2 emissions has led them to construct a CO2 injection system which allows them to inject excess CO2 from natural gas into a deep underwater trap called the Dupuy Formation, located two kilometers underneath Barrow Island. This system is projected to reduce greenhouse gas emissions by 40% and is fully supported by the Australian government (Chevron Australia, 2020).

Chevron is a well-respected energy corporation in Western Australia. The Gorgon Project alone is projected to contribute $400 billion to Australia’s Gross Domestic Product and $69 billion in taxes to the federal government between 2009 and 2040. With its booming natural gas industry in place, Australia is now a leading producer of natural gas in the world market (Chevron Australia, 2020).

Dawn Pisturino

Thomas Edison State University

October 27, 2020

Copyright 2020-2021 Dawn Pisturino. All Rights Reserved.

 References

Bishop, M.G. (1999). Total Petroleum Systems of the Northwest Shelf, Australia: The Dingo-

       Mungaroo/Barrow and the Locker/Mungaroo/Barrow. Reston: U.S. Geological Survey.

Blewett, R. (Ed.). (2012). Shaping a Nation: A Geology of Australia. Canberra: Australia

       National University.

Chevron Australia. (2020). Gorgon project overview. Retrieved from

https://www.australia.chevron.com.

Dampier Bunbury Pipeline. (2020). About dbp. Retrieved from https://www.dbp.net.au.

Geoscience Australia. (2020). Energy. Retrieved from

https://www.ga.gov.au/scientific-topics/energy.

Pipeline Safety Trust. (2019). Pipeline basics & specifics about natural gas pipelines. Retrieved

       From http://www.pstrust.org/wp-content/uploads/2019/03/2019-PST-Briefing-Paper-02-Nat

       GasBasics.pdf.

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