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Wet Gas Multiphase

Here you will find a list of the top questions and answers for Wet Gas Multiphase Flow Metering.  

Unlike other subsea flow metering technologies, the Solartron ISA multiphase wet gas flowmeters do not have retrievable electronics. There is a very advantageous reason for this.

Retrieving any equipment that is subsea, is both expensive, risky and requires additional complexity in design to allow retrievability which adds cost. If a subsea electronics module for a flowmeter needs replacement, production and hydrocarbon revenue will be delayed and significant costs will be incurred in retrieving and redeploying the equipment.

In many other manufacturers complex multiphase flow meters, communications bandwidth limits data transfer to the surface and therefore local [to the flowmeter] high-speed processing of radioactive or dielectric signals is essential. Solartron ISA’s philosophy has been to keep subsea hardware and sensors as simple and robust as possible and to carry out processing of flow meter raw data either topside in the platform control room or in some instances onshore. This removes the need for having an electronics module subsea entirely. Solartron ISA supplies redundant measurement sensors as a back up to individual sensor failure.

 

As the gas velocity and energy of the process increases the erosional effect of the process would increase. The studied erosional locations on the machined venturi are (see CFD snip below) on the convergent face of the venturi profile and not at any of the DP tapping points. Solartron ISA does not consider there to be any detrimental impact on flow measurement.



Erosional velocity can be calculated using API RP 14E. However, due to the specified values for the empirical constant ‘c’, very conservative results are achieved. When sand is present in the flow stream, realistic erosional data can be determined using DNV RP O50. Solartron ISA has conducted computational fluid dynamics (CFD) studies to estimate the erosional rates for Venturi based flow meters. The conclusion being that with the correct design and material selection, these devices are very robust and highly resilient to internal erosion.

Generally, Solartron ISA do not have concerns as such. 40 m/s is just into the start of the region where care must be taken to understand the likelihood of any erosional factors which may start to increase in significance. This is dependent upon process composition and sand/fines content. There is no reduction in performance or increase in measurement uncertainty when exceeding 40 m/s gas velocity. It is used as a soft limit point for triggering durability/erosion awareness. Materials with superior erosional properties such as Duplex, Super Duplex, and Inconel are chosen for the flowmeter body construction. Operating the flowmeter for short time periods above 40 m/s is typical and should be no cause for concern. However, if the gas velocity is above 40m/s continuously then considerations should be taken. Solartron ISA have performed FEA and CFD for erosion and can perform erosional calculations when required.


Why is it important…
This may be quickly explained by a quote from Dick Ghiselin, Offshore Magazine, 7th October 2013; “In deepwater areas, the cost of well intervention is a formidable barrier. A single intervention can cost many millions of dollars, and in many cases, the result is uncertain. There are no guarantees.” 

Solartron’s subsea flowmeters are engineered with full redundancy across instrumentation, communications, and flow computing systems. For pressure measurements, they also incorporate redundant pressure tappings. This design features comply fully with the requirements outlined in Section 4.3.6 of the API 17F 2023 Edition and to quote API “The purpose of redundancy in subsea control systems is to ensure high technical availability of the subsea production or processing system”.

For our multiphase wet gas meters this includes redundant differential pressure, line pressure and temperature measurement. It is common for a true redundant system to also have redundant flow computer capability in the topside control room. Systems can be wired to single or dual connectors depending on the customers cabling philosophy.

How does Solartron remove such uncertainties as referenced by Ghiselin?
Complex flowmeters often have to have retrievability designed into the system, however, the simplified nature of Solartron ISA’s equipment negates the requirement for ensuring the system is retrievable. Solartron ISA’s approach is to have minimal electronics subsea, avoid the use of nuclear sources and ensure redundancy in all sensor measurement, thus reducing the risk of failed subsea equipment.

Others with retrievable approach: local electronics / often nuclear / risk of large costs and operational downtime.


Solartron ISA’s Subsea Flowmeters are all SIIS compliant.

Solartron recognize that brownfield extension projects may require MODBUS communications, please contact Solartron for more information on how we can help extend field life.