David Rassam (KBR) described the use of dynamic simulation to predict operational performance of offshore and onshore production facilities. Three case histories were presented. ‘Project A’ involved modeling an onshore gas processing terminal with AspenTech’s Hysys dynamic simulator. The model encompassed the onshore terminal, five satellite drilling platforms and a central production platform. Dynamic simulation was used to specify new features of the onshore terminal. During the project, Hysys was extended with an anti surge controller algorithm from Dresser-Rand, stream multipliers and a component splitter. Head vs. flow rate plots were used to investigate compressor startup. The study concluded that suction throttling valves were required for the onshore facility, that hot gas bypass valves were not required. The Dresser-Rand anti-surge controller algorithm allowed for optimal sizing of anti-surge valves and controllers. Project B involved an offshore producer connected to a high pressure production manifold. Again, Hysys was used to model transient behavior of the gas compression system in the event of unplanned ‘upsets’ to normal operation. Hysys was again extended with an anti-surge controller algorithm. The study confirmed plant stability as the plant inlet flow was ramped. Project C investigated control and operations of a multiphase pipeline connecting a nine-slot platform to an onshore facility, in particular the ramp down of production to a rate suitable for pigging. Hysys and Scandpower Petroleum Technology’s OLGA 2000 were used to model the multiphase pipeline. The study confirmed the feasibility of a reduced production rate and allowed for fine tuning of slug catcher pressure controller set points. Rassam concluded that Hysys was a good tool for validating engineering design and for mitigating risk—eliminating the ‘element of surprise.’ Designers gained in confidence and were better able to meet environmental constraints and to define operating procedures.
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Martyn Johnston from Petrofac Consulting and Taoufik Manai, Schlumberger presented a paper on the use of Hysys to model the BG-operated ‘Armada’ facility. The Armada platform acts as a hub for six North Sea producing fields. Armada liquids are exported to Forties and gas to the Central Area Transmission System (CATS) gas pipeline system. Armada handles gas, gas condensate, volatile and black oil. Hysys is at the heart of the Armada integrated asset model (IAM) and of Schlumberger’s ‘Avocet’ vision to ‘streamline the entire reservoir and production system into a single workflow.’ BG’s interest in the Armada IAM was for life-of-asset development planning, in calculating ‘back-out’ and to study the economics of proposed modifications to the facility. Other model components included Petroleum Experts’ GAP multiphase gathering network modeler, Calsep’s PVTSim and Schlumberger’s Eclipse fluid flow modeler. Legacy spreadsheet-based models were ported to the Avocet infrastructure. Here the main issue was making the model sufficiently robust for use in the IAM. The solution was to make use of Hysys’ ‘user variables’ to tune the model for use in a range of studies. These included disconnecting network branches, shutting in wells and shutting in a whole field. Johnston concluded that integrated asset models are powerful tools for investigating the impact of proposed changes in reservoir management strategy. They are also useful in studying network hydraulics and facility sizing on lifecycle production and asset economics. Schlumberger Avocet IAM package proved a flexible, user-friendly framework for integrating many different applications including Hysys. The Armada IAM has proved to be a flexible tool for asset management, capturing the complex interaction between reservoirs and the top side network
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‘Pinch technology’ was the subject of a presentation by Shell’s Oscar Aguilar and Ashok Dewan. Pinch technology uses high tech thermodynamic modeling to optimize energy use across processes such as refining. The holistic approach to process design and optimization exploits the interactions between different plant units to optimize resources and minimize costs. Pinch technology was originally developed in the 1980s to reduce energy consumption but its use has now spread into other areas such as water and feedstock use and debottlenecking. Typically, pinch technology involves using the heat rejected by hot streams to warm cold plant processes.
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