Natural gas is exploited and brought to the surface through drilled wells. It is then treated and distributed to various consumers through various pipelines. The pipelines carrying natural gas can be classified based on their function (transportation system), access. jurisdiction & pressure of gas to be transported.
Classification based on the function:
- Gathering Pipelines: These are smaller interconnected pipelines forming complex networks with the purpose of bringing natural gas from several nearby wells to a treatment plant or processing facility.
- Production lines: The pipes or equipment which are near the wellhead or to the place of production which are used to produce & prepare the gas to transport.
- Transmission Pipelines: High Pressure (trunk) pipelines (typically 6-48 inches in diameter) that carry gas from source to end user or to pipeline network serving the users (around the country).
- Sub-transmission Pipelines: High Pressure pipeline connecting the main pipeline to the city gas station but is owned by the CGD entity.
- Spur Pipeline: These Pipelines are the branches of transmission pipeline taken out to serve one or more consumers.
- Distribution Pipelines: Pipeline system that delivers the natural gas to individual users or commercial/industrial customers and are operated at relatively low pressure.
- Dedicated Pipelines: Pipeline which is laid, built and operated for a particular customer either by the customer himself or by the gas supplier or by any third party.
Classification based on Access:
- Common carrier pipelines: Any pipeline which is used by more than one consumer on open access basis is called common carrier pipelines. The access to such pipeline is governed by the Access Code notified by PNGRB.
- Contract carrier pipelines: Any pipeline which operates under a fixed contract is called contract carrier pipeline. On conclusion of a contract, the contract may be extended or these pipelines are converted to common carrier pipeline by PNGRB’s permission.
Classification based on Jurisdiction:
- Interstate Pipeline: The pipelines that supply gas across the state boundaries.
- Intrastate Pipeline: The pipelines that supply gas within the state boundaries.
Classification based on pressure of the gas to be transported:
- The material of construction is chosen based on the pressure of gas being transported. Pipeline made of steel for high pressure, Polyethylene for medium & low pressure, & Copper/Galvanized Iron for very low pressure (risers & domestic connection). The steel pipeline network forms the primary network operating at pressure above 7 bar. The primary network supplies gas from one or more CGS to service line or distribution lines. The polyethylene pipe network is also known as secondary network operating at a pressure below 7 bar & above 100mbar. This network supplies gas to tertiary network & industrial consumers. The GI/Copper pipelines connecting the service regulators to household domestic connections operate at a pressure less than 100mbar & are also known as tertiary network.