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Flow Level Pressure
An Oil Company Used Dual-modality ECT and ERT to Study the Flow of Multi- phase Oil-water-gas Systems Reducing Energy Costs and Improving Plant Yields
Emeline Bodard, Industrial Tomography Systems Email:
marketing@itoms.com
Electrical tomography techniques provide the capability for flow visualisation, regardless of material opacity, to enhance the understanding of such complex flow processes.
Industry challenges
The petrochemical sector has invested a considerable amount of resources over the last decades trying to understand more about flow conditions, multiphase flow being one of the most challenging processes for the industry.
Multiphase flow occurs when two or more phases are flowing along a closed or open pipe. The phases may be gas, liquid or solid and two or three phase flow are common (as well as multiple component flow due to immiscibility in the liquids more that one liquid phase may exist). Hence in the “fluid” flowing down the pipe, the phases may be fully mixed, fully separated and anything in between depending on the nature and densities of the phases, the degree of turbulence induced in the mixture and the physical geometry of the pipe. Add to this the boundary layer effect at the pipe walls and it is a very complex measurement challenge.
Most of the current research and measurement systems rely on flow regime pre-determination, assumption or computational models.
There is a well defined need in knowing process conditions with certainty to improve efficiency and quality as well as reducing processing costs. It would be highly beneficial to measure the flow of each phase in the pipe, ideally mass, volume, phase inversion and the degree of mixing within the pipe.
Oil & gas companies are particularly interested in knowing which flow regimes (stratified, bubble flows, etc) they are working under at a certain time of their process. There is also growing academic and industrial interest in oil sands research where once again visibility is reduced due to stainless steel equipment or opaque material (sand in heavy oil). Additionally there is a need to learn more about wet gas flow behavior to improve understanding of meter performance.
Organisations from the mining and environmental sectors are involved in water based slurry research looking at the concentration, settlement and velocity of solids transported down a pipe by the liquid phase. This also provides a better understanding of corrosion effects.
technology, Electrical tomography has developed into robust technique for the characterisation of complex chemical processes. Tomography allows chemical process users to estimate the spatial distribution of phases and chemicals inside their processing vessels or pipelines, giving instant feedback on reaction processes, or efficiency of transport.
Technology principles
Industrial Tomography Systems plc (ITS), a spin-off of the University of Manchester was founded in 1997 to commercialise electrical tomography systems. ITS is today the leading supplier of Electrical Resistance Tomography (ERT) solutions. The company also supplies Electrical Capacitance Tomography (ECT) and ultrasound spectroscopy instruments.
Pipeline monitoring
ERT measures the distribution of electrical resistance (or conductivity) in a cross-sectional plane of a pipe or vessel: applicable to water/gas or water/solid flow. ECT is used where the bulk medium does not conduct electricity: applicable to oil/gas flow. Multiple modalities (of capacitance and resistance electrical tomography) have been fused to provide information on multi-phase flows.
Applications Water and sand flow visualisation:
CSIRO (Melbourne, Australia) required a measurement technique to measure the particle and fluid properties in solid-liquid flows for both research and industrial application. Measurements were performed on a 100 mm diameter flow loop with closely graded 2 mm silica sand suspended in clear shear thinning polymer suspensions. These ‘model’ suspensions mimic the behaviour of bimodal suspensions of particles containing a large fraction of fine theologically active particles that would form a non-Newtonian carrier in which would be suspended the coarser fractions such as those found on mining co-disposal lines.
ITS have developed polymer lined stainless steel pipeline ECT sensors for more demanding conditions. The electrodes are contained within a resin filled cavity between the polymer pipe linear and the external stainless steel pipe. The external stainless steel pipe ensures the pressure integrity, which is key in many petrochemical processes.
ITS is committed to the development of its range of sensors and is continually exploring novel techniques to deploy the technology in challenging operating conditions.
Comparison of a photograph, an MRI picture, an ITS p2000 online tomogram and ITS SCG offline tomogram
Sensor expertise
ITS has wide experience in developing electrical tomography sensors for a range of applications. In contrast to many systems-based measurement techniques, tomography sensors are able to rapidly sense throughout a volume. Thus providing a dynamic picture of what is going on inside a pipe or vessel, e.g. whether a system is homogeneous.
Electrical capacitance sensors have the advantage that they can be made in such a way that they are both non-invasive and non-intrusive. ITS can manufacture sensors in a variety of materials ranging from acrylic to PTFE.
Solution: Electrical Tomography Background
In the mid-1980s work started that led to the present generation of Process Tomography systems. At Manchester University there began a project on Electrical Capacitance Tomography for imaging multi- component flows from oil wells. A relatively new
For the measurement of 3-phase systems includ-
ing air, oil and water, ITS has developed a dual modality pipeline sensor, which combine Electrical Resistance and Electrical Capacitance tomography measurements. This combination makes it possible to measure both conducting and non-conducting phases in a process.
Robust sensors have also been deployed in marine (dredging) and mining application to provide information on solids flowing down a pipe.
Sand/Water online visualisation using ERT Oil & Gas flow visualisation
Polimeri a subsidiary of Eni S.p.A. sought a measurement system capable of multiphase flow visualisation in a pilot scale flow loop at their Novara Research Centre in Italy.
The Polimeri flow loop consists of a feed tank (which also acts as a liquid-gas separator), pump, 2” diameter pipe and a gas injection system. It is instrumented
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