Custody Transfer Measurement and the Changing Role in a De-Regulating Oil and Gas Economy

The oil and gas industry has an economic responsibility to itself, to have a fair basis for custody transfer of their products, says Trilochan Gupta

Oil and Gas Market Place
The oil and gas industry has an economic responsibility to itself, to have a fair basis for custody transfer of their products. This is best done by the application of factual, accurate and current measurement standards that give an equitable basis for the exchange of oil and gas products for money.
Globally, hydrocarbon custody transfer liquid measurement has made significant strides in the past several years towards an online, dynamic, continuous measurement approach using a displacement prover system, and away from batchtype tank gauging. One of the main reasons for this trend has been field verifiability, traceability, economics - with the cost of measurement inaccuracy a major factor, as well as personnel costs for operating, and maintenance. Also, some of the fluids being measured are defining new uses for old equipment, as well as requiring new equipment.
The challenge of flow measurement today is significant. The energy business, of which we are a part, is in upheaval. Several countries have moved from a regulated business to a competitive business. Our flow measurement knowledge requirements are greater than ever with demands for new governmental measurement regulations, new industry measurement standards, wider use of automation and higher efficiencies.
Though it is often said that custody transfer measurement has corporate character, unfortunately, quite often the custody transfer metering (and hence measurement) is an afterthought and the factors necessary to be controlled for good measurement are either ignored or thought to be of secondary importance.
Either with crude oil or processed hydrocarbons; oil and gas users in the Asia Pacific region have been successfully using large “Flow Metering Skids” with best practices for real time field verifiable, traceable dynamic custody transfer data for several years now. The concept of dynamic flow measurement through such “Measurement Systems” rather than through static tank measurement of batch operations has over the years allowed a more efficient usage of the operation people involved.

Flow Measurement or a Flow Meter?
This brings us to a basic decision that an oil and gas organisation must make: “Do we use a flow meter or do we use flow measurement?” By“using a meter” one simply states that he uses an Orifice, PD, Turbine, Coriolis or Ultrasonic technology device. That is, he must be aware of all ramification, - as a flow meter is only one fifth of the flow measurement equation. A high integrity Custody transfer measurement system is a result of careful design based on the application requirement comprising of fluid control, conditioning, metering, computation and a means of traceable site data validation.
Obviously, to solve the flow measurement equation it is imperative that every part of the equation must be well understood and represented and not just the flow meter alone.
Custody transfer management is more than just measurement hardware in the field. It is the entire chain from the conceptualisation of custody transfer metering to the final production sale data reporting.
For example, in the upstream oil and gas sector, measurement includes all intermediate steps such as measurement and sampling guidelines, operational procedures, data processing (PVT), data transmission and reconciliation, allocation or custody transfer procedures [8].

Custody Transfer,“Measurement System” and its Customers
In a de-regulated oil and gas economy, the report card of measurement measurement– purchases balanced against sales, with allowances for usage between, becomes a significant dollar consideration in terms of a company’s balance sheet, which is based on only “field measurement data”. With our market place history of over 70 years, we have witnessed in every de-regulating market “Custody Transfer Flow Measurement of Oil and Gas” takes centre stage. Of course, this is due to a variety of reasons such as changing corporate culture, the need to create brand equity of the Oil or Gas sold, and most certainly due to the direct impact these measurements have on the bottom line of the Oil and Gas companies as explained above. Today, India is well poised to repeat history with the phased, yet rapid de-regulation of this important industry segment in the energy chain....

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