In what is regarded as a minor revolution in oilfield flow measurement; MOL invented a viable answer to the dilemma after years of development. The oil industry everywhere has been grappling for decades with the problem of control in the early stages of oil and gas production without reducing the natural pressure of about 2 MPa (20 bar) inherent in the flow mixture, as this pressure negated the use of expensive pumps and related infrastructure. Reducing the pressure would further have led to the loss of valuable dissolved gas.
Hungarian oil and gas company, MOL, has reinvented the method for measuring and separating a pressurised mixture of oil, water and gas used in its early production processes, using Danfoss' MASS 6000 MASSFLO mass flowmeter.
Early attempts at measuring accurately at this stage of production - typically based on turbine systems taking out random samples for laboratory use - have not been able produce more than estimates under the 20 bar pressure level. It was a given that solving this obstacle would take the oil industry two major steps forward. Firstly, on-line measurement would make it possible to check the quality of each oil well and stop drilling when it was no longer profitable to continue. Secondly, significant savings and operational advantages would flow from extended, precise measurements in the form of decentralised, digital signal transfer to a medial point of process control.
Danfoss' MASS 6000 plays a vital role in the newly developed measurement system, now active in Hungary's biggest oil field (1000 wells). Mounted in the discharge pipe of a separator tank, it measures three parameters of the dynamically changing medium consisting of oil, water and dissolved gas. Together with the pressure value - supplied by a pressure transmitter - total mass flow, density and temperature is measured and communicated to a central computer where unique, patented software - developed in partnership with installation company Atys-Co - processes the data and transforms it into accurate, on-line information about the distribution of the three components.
To date, the Hungarian installation comprises 30 separator tanks, some of which take in running input from a group of wells, while others are test separators checking wells one at a time. In this way, the output content value from every well is known.
The MASS 6000 flowmeters are connected to the central process control system via a HART module for serial communication. Facilitating the transfer of more than one process parameter from each flow transmitter, the HART module allows all required information to be obtained using the same pair of wires, thereby significantly reducing project wiring, I/O requirements, installation and commissioning costs. In addition, it has made the remote configuration and diagnosing of each flowmeter possible.
MOL's choice of Danfoss as instrumentation supplier was based on several factors. "The selection followed testing of several massflow meters available," MOL production consultant, Imre Szl vik, explains. "Danfoss is locally represented in Hungary and respected in its field. In fact, several of MOL's test plants over the years used MASSFLO meters."
The Series MASS 6000 operates on Danfoss' new USM-II electronic platform, which supports add-on bus communication modules. This concept greatly contributed to the success of the MOL project. Because the same USM-II transmitter is used whether a communication module is fitted or not, development and process evaluation work was able to continue with fully functioning MASS 6000 signal converters using traditional analog outputs while Danfoss perfected the HART-protocol add-on module for USM-II. When the HART module was finished, the modules were simply plugged into the transmitter, adding full HART communication capability. It was not necessary to change or reconfigure the MASS 6000 signal converters.
If MOL should decide to migrate from HART to a faster, all-digital bus system such as Foundation Fieldbus or Profibus, it can be done without replacing the signal converters. This flexibility within the Danfoss design means that MOL's investment in MASS 6000 massflow meters is protected for longer than with traditional designs.
Mick Baugh, Danfoss
011 803 8390
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