Natural gas is one form of petroleum found in similar circumstances to crude oil and coal, i.e. originating from the accumulation of fossils, thus sometimes referred to as fossil fuel.
Petroleum consists mainly of hydrocarbons, that is a series of molecules containing atoms of hydrogen and carbon. When burnt, petroleum offers higher caloric value than woods.
Natural gas normally comprises of several hydrocarbon components e.g. methane, ethane, propane and butane, as well as carbon dioxide, nitrogen and liquid.
About 70% of most natural gas is methane. Various compositions can be separated out and utilised for various purposes.
Natural gas is usually used directly as a fuel for power plants, industries and vehicles, and when separated, can be used for a host of application.
Natural gas has a number of superior properties than other fossil fuels, being colourless, odourless, intoxic, lighter than air and flammable (flashing point at 5-15% of air volume and ability to self-ignite at 537-540 degree Celsius).
Natural gas offers high caloric value and complete combustion. Because of that it helps reducing the green-house effect that causes global warming.
Due to the fact that it is lighter than air, natural gas floats when it is leaked into the ambience and thus is safer to use.
It is relatively cheaper than other forms of petroleum such as oil. Yet it offers more added values.
Furthermore, most of natural gas supplies presently used in Thailand is produced locally and therefore reducing the country's import energy bills.
Inhaling excessive volume of hydrogen sulphide that comes with certain natural gas may damage tissues of the eyes and cause respiratory diseases.As natural gas is flammable, it can cause fire and explosion when it contacts with heat or flames.
It is prone to explode if significant volume of natural gas is accumulated in a confined area and catches fire.
LPG is derived from the separation process of oil and/or natural gas. LPG is normally referred to either the mixture of propane and butane or the whole part of each of the two gaseous components.
In Thailand, the LPG derived from the natural gas separation plants comprises 70% propane and 30% butane, and thus yielding a high caloric value. LPG can be used as a fuel just like natural gas.
In 2002, more than 60% of Thailand's electricity is generated by natural gas. About 77% of some 2,000 MMcfd of gas is directed to the Electricity Generating Authority of Thailand (Egat),
independent power producers and small power producers. About 8% of the overall gas is delivered to factories and 15% to natural gas separation plants as raw materials.
The natural gas substitutes fuel oil that costs the country tens of billion baht a year.
Natural gas procured by PTT comes from offshore and inland sources as well as from Myanmar (Burma).
Indigenous gas represents about 75% of total gas supplies with the remaining 25% from Yadana and Yetagun fields in Myanmar's Gulf of Martaban.
Field
Contractual volume ( Mscfd)
Reserves (Tcf)
Concessionaire
Erawan
230
0.82
Unocal/MOECO
Unocal 2 & 3
510
4.87
Unocal/MOECO/PTTEP
Bongkot
550
7.91
PTTEP/Total/BG/Lisbon Star Management
Nam Phong
60-90
0.37
Esso/PTTEP
Tantawan & Benchamas
125
0.81
Thai Po/Chevron/ Palang Sophon
Pailin
165-330
3.99
Unocal/MOECO/PTTEP/ Amerada Hess
Yadana
525
6.38
Unocal/PTTEP/Total/ Myanma Oil & Gas Enterprise
Yetagun
200-400
3.17
PTTEP/Petronas/Premier Oil/Nippon Oil/Myama Oil & Gas Enterprise
* JDA (Not in production)
390
6.27
Petronas/Triton
Natural gas from the Gulf of Thailand is rich with several valuable hydrocarbon components and PTT has built separation plants in Rayong and Nakhon Si Thammarat to extract them.
The gas separation plant maximises benefits from the natural resources, giving rise to a host of industrial development.
Products from gas separation plants are largely supplied as raw materials to the local petrochemical industries with some being delivered to other domestic industries and overseas buyers.
GAS Separation Plant in Thailand
"GAS Separation Plant" has thus emerged to add value to natural gas for Thailand's optimization of natural resources.
It has also entailed the development of numerous related industries.
The Petroleum Authority of Thailand (PTT), then, constructed Gas Seperation Plant Unit 1 in Mab Ta Phut Subdistrict of Rayong Province in 1982.
The inauguration ceremony of Gas Separation Plant Unit 1 was graciously presided over by His Majesty the King, Her majesty the Queen,HRH Princess Maha Chakri Sirindhorn and HRH Princess Chulabhorn on April 18, 1985
Later on, Gas Separation Plant Units 2 and 3, which came on-stream in 1991 and in 1997 respectively, were constructed in the same compound as Unit 1, in response to the increasing demand for ethane, propane, liquefied petroleum gas (LPG) or cooking gas), and natural gasoline.
The products have also been supplied as feedstocks of petrochemical industry. PTT's Gas Separation Plants can thus save energy imports,lower trade deficit, enhance the stability of petrochemical industry in Thailand's Eastern Seaboard, and create national energy security.
Gas Separation Plant Unit 4, of which official inauguration was held on July 12,1996, was aimed to satisfy the demand for LPG or cooking gas and natural gasoline, especially in the south of Thailand.
Natural gas used in Gas Separation Plant Unit 4 is from the Bongkot field, transmitted via a 32 - inch pipeline of 170- kilometer long to the Erawan platform and sent through a 24- inch and 160-km.pipeline onshore at Thong Nian Subdistrict,Khanom District of Nakhon Si Thammarat Province.
The construction of Gas Separation plant Unit 4 has facilitated and sped up product transport via tankers to PTT's LPG Terminals in Surat Thani and Songkhla, and enhanced convenience in product export.
Nevertheless, the continuously rising demand for energy resulting from economic expansion has raised the demand for natural gas. Concurrently, the demand for petrochemical feedstocks has constantly escalated.
Therefore, on December 22,1999, PTT's Board of Directors approved the construction of Gas Separation Plant Unit 5 to increase the production of ethane and LPG or cooking gas as feedstock for the expansion of Thai Olefins Public Company Limited (TOC).
Consequently, on September 27,2001, PTT's Board of Directors approved in principle PTT's support to the 300,000-ton-per-year ethylene capacity expansion project of TOC, using ethane as feedstock. In order to reduce the production cost,
the Gas Separation Plant Unit 5 Project is the first for PTT to be granted such investment promotion privileges by the Office of Board of Investment (BOI) as exemption of import duty on machinery and 8-year corporate income tax.
Production Capacity and Products of Gas Separation Plant Units 1-5
Gas In-Take Quantity
Methane (MMSCFD)
Ethane (Tons/year)
Propane (Tons/year)
LPG (Tons/year)
Natural Gasoline (Tons/year)
Unit 1 : 350 MMSCFD
250
330,000
191,000
243,000
76,000
Unit 2 : 250 MMSCFD
230
76,000
108,000
205,000
36,000
Unit 3 : 350 MMSCFD
315
111,000
201,000
250,000
36,000
Unit 4 : 230 MMSCFD
215
-
-
205,000
34,000
Unit 5 : 530 MMSCFD
337
520,000
151,000
495,000
177,000
The transportation of natural gas by pipeline dates back to 900 B.C. when the ancient Chinese used the bamboo tubes to deliver gas. In 1821, records showed that wooden tubes were used to transport natural gas in the US.
Today, a complex network of pipelines exists in many countries, providing a vital means of transportation of natural gas.
In Thailand, a natural gas pipeline network came to existence in 1981 when the then Petroleum Authority of Thailand (PTT) was tasked to build the kingdom's first gas line
stretching from Erawan gas field in the Gulf of Thailand to come ashore at Rayong before extending to Chachoengsao and Samut Prakan.
An extensive network of gas pipelines have been laid in Thailand both offshore and inland and as of 2002 involves a total length of 2,650 km, delivering more than 2,000 MMcfd of natural gas to power plants and various industries.
The process of laying land lines involves:
Preparation of construction area. Depending on the size of pipe and terrain, normally about 15 metres of horizontal spread of the lines are prepared to facilitate the transportation and movement of construction equipment.
The ground is leveled and the top layer of the soil is separated from all the soil excavated. Later, the top soil is returned to the area's surface after the backfill in order to allow plants to grow.
Transportation of pipes. Trailers are used to move pipes from stock yards to laying sites under the watchful eyes of specialists.
Ditching. A special piece of equipment is used to dig a ditch to the desired depth according to the pipe's size and construction specifications.
Normally, the pipeline is buried at least one metre under ground, or 1.5 metres if it was laid along the highway.
Pipe bending. The pipe is bent to the angle and elevation of the ditch. Pipe bending is usually carried out along the trench or at pipe storage yard with minimum effect on pipe coating.
Pipe connection and X-ray. Normally, a pipe is 12 metres in length to facilitate pipe connection in the construction phase.
Each section of the pipes is welded together and thoroughly checked by X-ray.
External coating. Before being lowered into the trench, pipelines are protected externally against corrosion by a coating of epoxy and high density polyethylene.
Lowering pipelines into the ditch is carried out by tractors.
Backfill is carried out in such a way that ensures sufficient padding and bedding to protect against damages to the pipes. Top soil is put back to the surface.
Land restoration. After the backfill, the soil and environment of the pipeline is restored to the original condition,
though planting of big trees in the pipeline's proximity is avoided to prevent their roots from causing damages to the coating.
1.
Opening drilling
Sections of pipeline that cross water ways are coated with epoxy and concrete which prevents the line from floating.
Detour roads are built or iron sheets are laid over the construction sites in order not to cause traffic problems.
Digging of ditch in the water ways will not be carried out before the pipeline is laid to the area in order to minimise sediment accumulation.
Applying methods to reduce sediment accumulation in the water ways resulting from the activities such as installing filters.
Grading the area and remove equipment out of the construction site as soon as the work is done.
Compounding the area to prevent collapse of upper soil.
2.
Drilling
Undertaking the activities without disturbing the traffic flows.
Use casing tubes to penetrate the hole.
Inserting the actual pipeline to the casing tubes.
Pulling out the casing tubes.
3.
Horizontal directional drilling
Pinpointing the exact entrance and exit of the pipeline before commencing drilling
Allowing a minimum 5-metre parallel distance to any other pipeline routes
Remove soil, mud and chemicals which come out from the operation and treated them under government-guided procedures.
Directional drilling should not cover a distance of one km and depth of 30 metres. Laying Pipeline Under Roads
If the pipeline was to be laid through main roads, use a driller to drill a hole underneath in order to prevent traffic disturbance.
or small roads with less traffic, a ditch can be dug with a detour road being built or that the trench is covered by iron sheets to allow vehicles to pass over.
The pipeline is installed by a "lay barge" which winches itself along the route laying the pipeline behind it.
Individual coated pipe lengths, usually 12 metres, are welded on the barge and the completed is fed to the sea bed along a structure projecting from the barge known as a "stinger."
When it approaches the coast, the pipeline is laid in a trench and buried in the depth depending on the condition of the environment.
On the shore, there is special equipment that pulls the pipeline onto the land.
Gas pipeline
Gas pipeline is made of high-tension steel under international specifications and tested before being delivered to contractors.
Its strength varies in accordance with the application requirement.
The diameter of pipeline determines the gas flow capacity, while its thickness is dictated by maximum pressure of the gas,
tension during the pipe laying, external pressure and environment within which the pipeline is installed and operates.
Designs of pipeline conform with ASME B31.8 Gas Transmission and Distribution Piping systems established by the American Society of Mechanical Engineers (ASME).
Corrosion
Coating is applied to pipeline to prevent external corrosion. For submarine pipelines, two layers of coating are applied - corrosion coating and concrete coating.
The latter also prevents the pipeline from the impacts created by fishery and marine activities.
Once installed, cathodic protection designed for 40-year protection, is also applied by means of impressed current or sacrificial anodes,
dependent primarily on the resistivity of the soil and the composition of the natural gas put through the pipeline.
Hydrostatic testing is applied to see whether the pipeline can withstand with a set maximum pressure.
For inland pipeline, the testing standards are 1.25 to 1.4 times over the design pressure, and 1.25 times for offshore pipeline.
Control and Communication
Gas transmission is controlled and regulated by a Supervisory Control and Data Acquisition system, or SCADA.
The system is mainly operated around the clock by PTT's Chon Buri Operation Centre.
Along the pipeline, there are block valve stations which control pressure, temperature, density and volume of natural gas put through.
In compliance with the international standards, a block valve station is built at least 7.5 metres away from the pipeline.
A concrete wall is also put in place at the station located in the high-traffic area.
In any abnormal circumstance, the valves at the block valve stations are turned off by a direct control from the Operation Centre.
The control systems go through several communication modes, namely microwave, optic fibre cable, satellite telecommunication,
UHF (Ultra High Frequency) and VHF (Very High Frequency) radios, dedicated PTT internal telephones and TAT phone network.
Inspection of the pipeline is normally carried out by cars and aircraft. In the jungle area, the works are done by foot.
Inspecting the internal part of the pipeline is by means of sending an Intelligent PIG (Pipeline Inspection Gauge) into the line to collect
and analyze data and pinpoint the area where special attention is required ahead of time of damage.
Intelligent pigging is implemented every five-year period. Inspecting by pigging is performed by all leading oil and gas companies.
Specifically, it looks into the pipeline's thickness, dents, shifting, damaged area, external and inside corrosion. While performing it task, a PIG does not interrupt the transmission of gas.
PTT's pipeline inspection is performed under the TISI 18000 safety standard.
Odourant
An odourant called Ethyl Mercaptan is added to natural gas before it is released to users to alert members of the public in the case of gas leakage into the atmosphere.
Ethyl Mercaptan is the same odourant included in LPG.
Indeed, the ASME B31.8 standard thus applied has already taken into account minimising the impacts on environment and community where the pipeline is laid.
However, practically in Thailand, all the petroleum transmission projects are required to conduct environmental impact assessment (EIA)
study under the stipulations of the Office of Environmental Policy and Planning, Ministry of Science, Technology and Environment.
The study must spell out measures to minimise environmental impacts before, during and after the construction.
The measures must be integrated with engineering of the projects and strictly observed.
However, the environment may be affected temporarily, about 3-4 months, during the laying of the pipeline. But after the backfill is completed,
the environment can be restored close to its original condition, except that no trees are planted and buildings constructed in the stipulated parameter of the pipeline.
Contractors must offer an one-year warranty for the pipeline they lay. Meanwhile, PTT continues to look after the environmental impacts of the pipeline.
Gas pipeline has been regarded as one of the most efficient, safest, economical, environmental friendly mode in transporting the energy in great volume without causing traffic problems.
