The handling and transfer of fluids is a mission-critical process of any oil and gas operation, requiring several core components such as valves and pumps placed optimally within a production system.
Valves are mechanical equipment designed to direct, start, block, control, mix and regulate a process fluid’s flow, pressure, or temperature, making them essential for oil and gas production, particularly in deepwater exploration and processing in floating production storage and offloading (FPSO) units. Pumps are utilised in virtually every phase of oil and gas operations, from transferring crude oil into tanks to delivering hydraulic fluid to drill bits and circulating drilling sludge back to a storage tank for repurification.
FPSO platforms receive hydrocarbons from subsea oil wells for processing and separation into produced water and natural gas. During this process, valves and other equipment are exposed to corrosive chemical compounds, necessitating the specification and manufacture of valves using various metal alloys.
A research report by the Offshore Division of the United Kingdom’s Health and Safety Executive (HSE) found that most failures relating to valves in operation were associated with the incorrect selection of the valve type and materials.
In a sample of 253 valves exhibiting operational defects, 43 per cent of the identified causes were linked to issues such as internal and external corrosion, mechanical failure, mechanical fatigue, and metallurgical defects in the materials.
Some types of valves include ball valves, which function as on-off operators using a ball with a through-hole as the obturator.
When in the open position, the ball’s passage hole is fully aligned with the pipe, allowing fluid to flow. In the closed position, the ball orifice is perpendicular to the flow direction, blocking fluid passage.
A trunnion ball valve has the ball bi-supported by axes, where the sealing component is called the seat ring and moves in a piston effect, performing the upstream sealing at the valve’s internal cavity entrance.
Floating ball valves permit the ball to move freely, allowing it to shift towards the sealing ring when in the closed position.
Valves are usually constructed with a carbon steel body and stainless steel internal components. However, for equipment exposed to the most corrosive conditions, all valve components are made from stainless steel.
The function of carbon steel as a valve body is to contain pressure. In some cases, metallic or polymeric coatings are applied to internal interfaces that come into contact with the fluid.
These coatings are typically applied through an overlay cladding welding process, utilising anti-corrosive superalloys based Stainless steel is categorised into four groups: martensitic, austenitic, duplex, and super duplex, each with distinct applications in oil and gas production.
Martensitic stainless steel contains about 13 per cent chromium in its composition and is used internally in valves. Like carbon steel, it serves the function of controlling pressure or flow.
Austenitic steel is also used in parts that contain pressure and has good corrosion resistance, a result of nickel, chromium, and molybdenum alloys.
Duplex stainless steel can be used for both external and internal valve components, and uses a two-phase microstructure with balanced proportions of austenite and ferrite.
Duplex components are often used offshore as they have high corrosion resistance and exceptional mechanical strength.
Adding alloying elements like copper and tungsten to certain duplex steel grades, such as the commonly used UNS S31803, produces super duplex steel, which offers enhanced resistance to chloride corrosion.
However, this steel has a low machinability due to the high presence of alloying elements, low thermal conductivity, high temperatures in the cutting zone, high degree of work
hardening, and a higher production cost.
PUMP OPTIMISATION USING NEW TECHNOLOGIES
Centrifugal or dynamic pumps are the most widely used in the oil and gas industry, employed for hydrocarbon processing, refining, water injection, and pipeline services.
They operate by utilising centrifugal forces generated from the rotation of a pump impeller, or driven rotor, to draw fluid into the pump’s intake and propel it through the discharge section.
Single-stage centrifugal pumps are primarily used for transferring low-viscosity fluids that require high flow rates and are typically utilised as part of a larger network of pumps.
These networks comprise other centrifugal pumps, such as horizontal multistage pump units for crude oil shipping, or water injection pumps for secondary oil and gas recovery.
A study published in Wireless Communications and Mobile Computing proposed a practical solution for enhancing pump efficiency using the Internet of Things (IoT). The oil well examined experienced a 90 per cent increase in production rate with the application of this new technology.
The research introduced a method to analyse essential parameters, including pump efficiency, tubing pressure, casing pressure, hydraulic pressure, and pump speed. This understanding allowed for the integration of the data into AI prediction models.
The future of oil and gas is the industrial IoT, according to the researchers, which will optimise both the upstream and
downstream sectors and reduce maintenance costs, improve production, and increase reliability.
Shell has successfully implemented AI at its Perdido platform in the Gulf of Mexico, which is one of the deepest floating oil and gas platforms globally.
Perdido experienced periodic disruptions in its pumps, which are responsible for separating oil and gas at a depth of 2,400 metres. Each pump transmits streams of information, including temperature, pressure, and chemical signatures.
By utilising AI to analyse patterns in data collected from the pumps over five years, a refined algorithm was able to identify the chemical fingerprint preceding 70 per cent of pump disruptions. This capability enabled Shell to predict potential disruption events and avoid lost production.
Another paper published in 2020 discussed the application of IoT-based technology to identify, control, and predict cavitation occurrences in centrifugal pumps, which are the most widely used pumps for fluid delivery.
The study simulated cavitation in both good and faulty centrifugal pumps, while sensor configuration and numerical data analysis were undertaken using an artificial neural network as the machine learning algorithm.
According to the authors, the findings would help pump manufacturers mitigate cavitation in centrifugal pumps from the design phase. They would also aid in predicting and effectively controlling cavitation during pump operation.
