The process of extracting oil and gas resources, processing them, then delivering them to where they are required is dependent on an array of pumps and associated equipment. This is true regardless of whether the oil and gas in question comes from conventional or unconventional reservoirs, from fields located onshore or offshore, and whether it is destined to supply domestic markets or for export. In this article, we take a look at some of the types of pump playing key roles in enabling Australia’s oil and gas industry.
Australian oil and gas resources
Oil and gas resources are located in either conventional or unconventional reservoirs, which can be located in either onshore or offshore geological formations.
The key difference between conventional and unconventional oil and gas relates to the geology of the reservoirs where deposits are located.
Conventional gas reservoirs consist mostly of porous sandstone and are capped with impermeable rock, which traps the gas and stops it from reaching the surface.
This means these reserves can be extracted by drilling wells through the cap rock, through which the oil and gas then flows to the surface. Conventional resources are located across Australia in both on- and offshore reservoirs.
Developed offshore oil and gas resources in Australia are conventional resources. Although the extraction of offshore unconventional resources is theoretically possible, the technological challenges of doing so mean that it is considered uneconomical compared to extracting other available hydrocarbon resources.
Unconventional oil and gas – which includes shale oil and gas, tight oil and gas, and coal seam gas – is contained in more complex geological systems that complicate its extraction.
As a result it cannot be extracted via traditional wells and requires innovative technology and techniques for extraction.
This often involves the use of hydraulic fracturing (or fraccing), which involves pumping a fluid mixture made up of water, sand and chemical additives into the wellbore under high pressure to create cracks in the deep rock formations to free the trapped hydrocarbons.
In the past, the cost of this process was considered to outweigh the potential gains. As a result, the extraction of unconventional oil and gas resources is a relatively recent development compared to conventional oil and gas.
However, in recent years technological developments have made fraccing more economical and these resources are now being developed, with most unconventional gas in Australia to date coming from Queensland’s CSG projects.
Close to the source: upstream applications
For onshore unconventional hydrocarbon resources that require fraccing, specialised pumps are needed for various applications including:
- Transporting the water required for fraccing to the well site
- Pumping fluid into the wells at high pressure for the fraccing process
- The transportation of produced water away for treatment and/or reuse
- To transport the extracted gas and/or oil to processing facilities
While conventional oil and gas resources, and some CSG resources, do not require water to be pumped into the ground for hydraulic fracturing, they do require pumps for an array of other applications.
For instance, CSG wells that don’t require fraccing still require the removal of some of the water trapped in the coal seams so that the pressure holding the gas to the coal is reduced, allowing the gas to flow to the gas well.
This is usually achieved through the use of progressive cavity pumping systems, which are lowered inside the well casing on steel tubing to a depth of around 800 to 1,000 metres – depending on the location of the coal seam.
Both the gas and associated water are then extracted via the CSG well, and are then separated and pumped to relevant treatment facilities via separate pipelines. At the gas processing facility the gas is compressed to high pressure using a multi-stage reciprocating gas compressor.
Gas is generally dehydrated before it is transported via a high pressure gas pipeline. This process may involve monoethylene glycol (MEG) injection or triethylene glycol (TEG) dehydration.
This process usually involves centrifugal pumps for recycling the separated glycol and reciprocating pumps to reinject glycol at the wellhead.
Crude oil is generally piped to a refinery for processing into products such as petrol, diesel fuel, liquefied petroleum gas (LPG) and others.
Processing plants require an array of pumps for applications including transporting hydrocarbons throughout the process, transporting boiler feed water, cooling, transport and metering of chemicals, acid gas removal, and booster services.
Pumps that handle hydrocarbons during processing are generally API 610 centrifugal process pumps.
Pumping may also be required for water injection to boost the flow of declining conventional wells, onshore or offshore.
Additionally, the process of extracting oil and gas often requires application-specific chemicals at precise quantities, requiring pumps that can handle these materials and deliver the required accuracy and reliability.
For example, an offshore oil and gas platform may have up to 100 metering pumps, often diaphragm pumps, installed.
Pumps are also often required to transport fluids needed for cooling, removing slurry, control of drilling mud, multiphase application, separating components, boosting pressure, emptying tanks, and other functions.
It is worth noting that associated and ancillary facilities at any oil and/or gas field will also require pumps to provide a variety of services.
Pipelines and transport: midstream applications
Oil and gas resources often need to be transported over large distances from their point of extraction, necessitating the use of pipelines.
Functions of transmission pipelines in the oil and gas industry include transporting hydrocarbons from extraction wells to processing facilities, transporting natural gas to end users, or transferring hydrocarbons to additional processing plants to be prepared for export.
Common types of energy pipelines in Australia include natural gas pipelines, liquid petroleum pipelines, and crude oil and condensate pipelines.
Australia’s natural gas network is particularly extensive, comprising more than 47,000km of natural gas transmission pipelines across the country.
In order to keep the hydrocarbons flowing through the pipelines under high pressure, pumping stations, known as compressor stations, are located along the pipelines. The intervals at which these compressor stations are placed depends on factors including the length of the pipeline, pressure, and other conditions.
The compressor units at these stations are usually centrifugal compressors, powered either by turbines powered by some of the gas from the pipeline or by electric motors, or reciprocating compressors.
In addition to compressing the gas to maintain adequate pressure throughout the pipeline, compressor stations also generally include scrubbers, strainers or filter separators, which remove liquids that may condense out of the gas as it travels through the pipeline, dirt, particles, and other impurities from the natural gas.
They may also incorporate cooling systems to counter increases in temperature during the compression process.
Compressor stations also play other important roles such as incorporating safety features and emergency shutdown systems, enabling gas to be rerouted into storage areas if necessary, and may incorporate infrastructure to enable PIGs to be launched and received to clean and maintain the pipeline.
LNG for export
Natural gas that is destined for export must first be converted to liquefied natural gas (LNG). In this case a pipeline will carry it to an LNG plant.
LNG plants produce LNG and condensate (natural gasoline) products, and in some cases LPG (propane and butane).
An LNG plant will have vast numbers of pumps – over a thousand is not uncommon – to support its operations. These pumps cover a wide range of duties including water, chemicals, hydrocarbons, and lube oils.
A range of specialised pump types including centrifugal, high-speed centrifugal, positive displacement, metering, and cryogenic pumps are involved.
Major pump services at a LNG plant include:
- Solvent/amine circulation pumps
- Reflux for scrub column and fractionation towers
- LNG product pumps
- Seawater pumps (if facility is seawater cooled) or fresh water pumps
- Hot oil or water pumps
Solvent pumps, at the acid gas removal unit, are often the largest pumps at a plant. This service is often split into two parts.
The first part involves a low head pump working at high temperature, then this is followed by a high head pump operating at near-ambient temperature.
Using the low head booster pump at the high temperature avoids problems with cavitation within the pump that would occur if the high head pumping were done at high temperature.
The gas leaving the acid gas removal unit is saturated with water from the amine solvent, and a dehydration unit removes the water.
The gas is then transferred to the mercury removal/scrub column, where a multiple stage propane refrigeration system chills the gas through a series of heat exchangers down to around -30°C.
The natural gas drops out liquids at this temperature, and the scrub column removes these heavy liquids (especially benzene and other aromatics), which would otherwise freeze in the main cryogenic heat exchanger.
The reflux pumps for the scrub column operate at about -30 to -50°C, and in the fractionation unit the de-ethaniser reflux pumps also operate at about -30°C.
After this, the gas enters the main cryogenic heat exchanger (MCHE) where it is cooled down to about -160°C.
At this temperature the natural gas is a liquid at atmospheric pressure.
The LNG product pumps used in this process are specially designed for cryogenic service and mounted, along with their motors, inside a container, which is flooded with LNG during operation. The suction of the pump is at the bottom of the container and the LNG discharge flows through the motor, providing cooling.
When the LNG is ready for shipping, loading pumps move it from storage tanks onto the LNG carrier.
These ships for LNG transport generally have two different types of pumps. These are the large cargo pumps for transferring LNG, and the small spray pumps, which provide LNG for the spray ring that helps keep the entire storage container cool.
Other pumps that play vital roles at LNG plants include heating pumps to circulate hot oil or hot water for elements of the plant, such as the amine stripper reboiler that require heating; and various water pumps, which perform functions including cooling using seawater or freshwater.
Key considerations for pumps in oil and gas applications
Throughout every step of the extraction, transportation and refining processes, hydrocarbon applications tend to be highly demanding, requiring equipment of the upmost quality and reliability.
Pumps in the oil and gas industry are frequently required to operate under extreme environmental conditions, which may include extremely high temperatures and pressures, or extremely low pressures and cryogenic temperatures, depending on the specific application.
Pumps must be composed of materials capable of withstanding their operating conditions and be non-reactive with any chemicals they will be exposed to.
Material choice is often governed by the prevention of corrosion, oxidisation and build-up on pump components. Some pumps must also be able to handle abrasive or volatile materials.
Often pumps and other equipment must be highly specialised to the application for which they are required, and must also conform to a variety of standards.
For instance, process pumps handling oil and gas must often conform to the American Petroleum Institute (API) 610 standard for pumps handling hydrocarbons.
As these process pumps must handle hydrocarbons at extremely high pressures and temperatures, with the risk of explosion if they are inadvertently released, the integrity of the pump casing is the foremost priority in their design and construction.
Failure of pumps in oil and gas applications can come at huge financial cost, and pose safety and environmental hazards, making the reliability and safety of pumps and systems extremely important.
Apart from fulfilling duty requirements and flow rate, other important considerations in oil and gas applications may include precision in metering, flexibility of operation, efficiency, and maintenance requirements.
In some cases, such as for pumps that might need to be moved between wells upstream, portability may also be an important consideration.
These are just some of the many factors that must be taken into account when specifying pumps and associated equipment for oil and gas applications.
In an industry with little room for error, quality, fit-for-purpose and reliable pumping equipment and systems are vitally important for efficient, safe, compliant, economic and effective operation.