Special Report: Modelling pipeline hydraulicsby Arabian Oil & Gas Staff on Jan 12, 2017
In recent years, as oil and gas fields become less accessible and their hydrocarbon quality lower and more variable, maintaining or increasing production levels has emerged as a key field development goal. One of the most pronounced challenges in meeting this goal is managing the complex hydraulics of pipelines used in gathering systems and to transport the oil and gas from wells to processing facilities.
As these pipelines get longer in new fields, deeper in offshore environments, or simply older in aging implementations, exploration and production (E&P) companies face critical problems for which they need better performance predicting and troubleshooting tools. From a business standpoint, solving these technical challenges is an increasing priority, since the capital expenditures involved in constructing and retrofitting gathering systems are a high proportion of development costs, but pale in comparison to the possible loss in field profitability due to flow interruptions.
There are many benefits to modelling the entire gathering and production system (be it offshore, onshore, topside, etc.) within one tool, including not only being able to optimise the design from a capital and energy perspective, but also ensure the overall safety of the system.
Accurate modelling of hydraulics
One of the key expectations in the modern energy production is reliability. In the industrialised societies, the need for reliable energy sources is paramount, and therefore the need for reliable sourcing is fundamental. This reliability starts with the exploration phase of the oil and gas fields. Since the formation of these fields is a natural phenomenon, the composition of the material extracted is unknown. However, there are tools the E&P companies can use to reliably extract these resources, even with unknown compositions.
The design of any gathering system and production network must contend with a variety of ever-changing business priorities and engineering constraints – with reliability being the constant objective. The system must achieve maximum uptime and performance to support the expected production throughput efficiently.
A second objective is to support changing hydrocarbon compositions, which naturally differ over the lifetime of a production field, but also change unpredictably due to new and unconventional production flows being fed into the gathering network. While the typical production involves an oil phase, a gas phase and a water phase, sometimes solids, such as sand and gravel also get mixed into the flow, depending on the field geology and its age. All of these factors need to be taken into consideration when an extraction strategy and the pipeline gathering network are developed.
The design of the pipeline network is fundamental to ensure the flow from the field is consistent and steady, so that downstream processing can be equally steady and uninterrupted. The integrated consideration of the pipeline network, its hydraulics, and the separation and production systems is critical to ensure that safe operations are correctly built into the design.
The pipeline network must be designed in accordance with industry standards such as API, ANSI and ASME as well as environmental (EPA), safety (OSHA), and any national, state, regional, or local regulations. The engineering design must take into account the envelope of expected temperatures, pressures and volumes of the mixture going through the pipeline, as well as the entire geography it covers to transport the products, and environmental conditions and restrictions along its path.
Need for better simulation
With a growing number of fields being located offshore or in hard-to-reach areas, pipelines have become increasingly longer and the surrounding environment more diverse, creating the need for better simulation of these new characteristics. It is also important to consider possible flow composition changes along the lifecycle of the field, depositions of impurities on the pipeline walls, such as wax and asphaltene, as well as the corrosion of the pipes and slugging.
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