Subsea processing

Another trend is to move processing equipment to the seabed, known as subsea processing. This requires reliability with regard to process control and stabihty/durability. In particular, sand handling is often a concern. The first subsea separation unit is due for installation fliis summer, at Norsk Hydro s Troll field (25). 

ABSTRACT Article has presented a numerical simulation method which was applied to analyzing Internal flow filed of the subsea gas-liquid hydrocyclone separator with Mixture model and RSM. The law of internal flow field distribution and separation characteristics of two-phase flow were obtained with the numerical simulation. Optimized separator structures were obtained with structure optimization design by simulation analysis. The numerical simulation can provide experiences for further study of subsea process equipment research and numerical simulation of hydrocyclones. 

Subsea processing can be an opportunity for PI, but the need for a nearby host is... 

Looking at a recent (2007) Scottish call for research proposals in the area of innovative subsea technologies, areas of general interest are enhanced subsea recovery, ultra-deepwater activities, subsea processing and equipment operation in high temperature and/or high pressure environments. PI could feature strongly in a number of areas as follows ... 

Subsea desalination Down hole compression/separation Subsea processing ... 

The reason for the strong interest in enhancing subsea recovery is that recovery rates for wells are frequently only 70% of the equivalent from platform-driUed wells. Cost-effective ways for increasing these recovery rates are needed. In the case of subsea processing, the need is to transfer much of what is done on platforms onto the sea bed. In addition to cost reduction, it would reduce the number of personnel stationed in dangerous environments. 

The crude separation facilities for a possible Troll oil development are shown In Fiq. 6. The crude stream from subsea wells with an expected platform arrival temperature of circa 5°C will be warmed by heat exchange with the export crude free water is knocked out In a 1st stage separator and the crude 1s then heated to the desired process temperature (> 40°C), prior to entering the second stage separator. Provision for the injection of demulsifier is required at the wellhead and upstream of the crude heater. 

Parkes, R. J., Cragg, B. A. Wellsbury, P. (2000). Recent studies on bacterial populations and processes in subsea floor sediments A review. Hydrogeology Journal, 8, 11-28. 

Special equipment was worked out for ECM and combined processes in a subsea environment for acquiring metal construction defective zone samples for detailed studies in the laboratory or for the total removal of the defective zone (for instance, crack zone) to prevent the defect from growing, drilling small holes at the ends of the crack tip to prevent tip propagation... 

Regulation 11 in the Pipelines Safety Regulations (1996) requires that the operator shall ensure that no fluid is conveyed in a pipeline unless the safe operating limits of the pipeline have been established. In order to meet this requirement, inspections will be carried out and analyses undertaken in order to determine the maximum allowable operating pressure (MAOP) for the subsea pipeline. Typically, the process for such an assessment will be undertaken in a manner as described by Hopkins et al. (2001) and shown in a flowchart in Figure 1.4. This process shows the progressive... 

It would appear that the question of uncertainty is a reoccurring theme in this instance. The subsea pipeline assets will display a high degree of uncertainty in relation to their current condition, approach to be adopted to allow for accurate inspection, which in itself will be subject to a level of uncertainty in terms of accuracy and reliability of measurements, as well as the levels of uncertainty inherent to the scheduling process. A question presents itself as to what is the best way to address these areas of uncertainty. One way to approach it is nicely put by De Neveville (2003) Understand that uncertainty is not always a risk to be avoided but also presents valuable opportunities that can be exploited. The case in point can be seen from the potential cost saving to be made in terms of being able to effectively extend the operational life of a subsea pipeline asset. 

Shutdown all process equipment Shutdown all chemical injection Offshore shut subsea production valves... 

For the purpose of illustrating the various steps in the reliability quantification process, a simplified case example has been used in this paper were application of subsea gas compressors are evaluated. This case example has been used throughout this paper to illustrate the process however the example has been modified and simplified to fit the purpose of this high level presentation of the research work which has been conducted when develop this guideline. 

In this technical paper the application of a subsea wet gas compressor has been selected as the case example which is used to demonstrate the key steps in the reliabihty quantification process for novel technology. Before presenting the main steps in the work processes defined in Figure 2, it is important to understand some... 

In the next section in this technical paper each of the main steps in the reliabdily quantification process is described in more detail based on the case example with the subsea wet gas compressors defined previously. 

The principles for the FSM technology were developed by researchers at SINTEF in Norway in the 80s. It was commercialized by the Norwegian company CorrOcean in 1991 and further developed for use on subsea oil and gas pipelines from 1994. FSM is now used at many locations worldwide, both top-side, underground and subsea. Systems are being operated under various enviromnental conditions from extreme heat in the desert to extreme cold. The project to adapt the technology for refineries and process plants was commenced in 1997, with financial support from Shell and Elf. FSM-IT now has well over 400 sensing matrices installed. 

Subsea gas-liquid separation of multiphase well flow, produced-water reinjection and multiphase one-way transportation of gas and crude oil can be achieved by Subsea gas-liquid hydrocyclone separator systems during the prophase subsea separation and processing. The gas-liquid hydrocyclone separator is the key equipment of the separation system, which can reahze gas and Uquid hydrocyclone separating based on the principle of density difference of the gas and liquid (Zhao Guoqing, 2003). 

It may be argued that the ultimate result of the intensification of offshore plant would be to make it disappear - either by doing away with it and using multi-phase pumping to carry the fluids ashore, or, as indicated earlier, to carry out the processes on the sea bed or subsea. Multi-phase metering permits produced fluids to be metered locally, so they could then be combined with flows from other weUs to share pipelines and processing infrastructure. 

Subsea PSD system The purpose of the subsea PSD system is to control abnormal operating conditions by stopping hydrocarbon flow by shutting down processes. Two such processes are ... 

The case-study is based on an actual sand erosion issue present in an offshore oil production system. Material degradation due to processes of erosion/corrosion is the main focus. The production system is located subsea and connected to a spread-moored FPSO (Floating Production Storage and Offloading) unit, which is used as a hub, processing the fluids produced from the subsea wells. 

The 700ppm initial diluted concentration was increased to 900 ppm after the injectivity test to obtain the design viscosity of 3.5 cP at top of the riser (corresponding to a 2.9 cP viscosity at reservoir corrditions low shear and 50°C) and take into accoimt some degradation ditring the process and the transit through the choke at the subsea Christmas tree level. 

It thus seems that these parameters are promising for the formulation of a model for re-entrainment in demisting cyclones. We are of the opinion that the formulation of such a comprehensive model should be an important research priority for the near future, particularly in light of the intensifying interest in off-shore, subsea natural gas processing. 

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