A leading oil and gas operator in South East Asia commissioned NEL to undertake the system design for an allocation metering skid. This system was part of the equipment required for the development of a marginal oil field. However, several unexpected issues were discovered that made it clear that non-ideal conditions would be present at the point of measurement. NEL resolved these challenges in a cost-effective way, demonstrating the company’s expertise in dealing with multiphase flow.
Based on the client’s specifications, NEL designed an allocation metering skid to measure single phase oil. The main pieces of equipment specified for the project included a 3-inch Coriolis flow meter, temperature, and pressure measurement system, a sampling system and water-in-oil monitor and a flow computer.
Shortly before commissioning, it was discovered that the expected fluid composition would be close to its vapour pressure and that the allocation measurement skid pressure drop would encourage gas to break out of solution. The resultant measured fluid would then consist of a two-phase and three-component mixture that would have adverse effects on the performance of the specified Coriolis meter (a single phase device).
This put the project in jeopardy, as over £200,000 had already been invested, and any additional expensive equipment or reengineering would, potentially, make the whole scheme uneconomical.
Based on its expertise working with two-phase and multi-phase flows, NEL formulated a solution that would minimise additional costs and allow the measurement skid to attain the required levels of measurement accuracy.
NEL used a correction method based on the meter’s performance in three-phase flows. In order to characterise the meter, it was first tested in NEL’s multiphase flow facility under the non-ideal conditions that would occur in the field. The meter’s outputs were compared with reference value and correction curves and lookup tables generated to allow the necessary corrections to be made. The corrected system was put in place and functioned well, although further re-calibration was necessary, as the installation did not achieve the flow-rates that had been expected.
Benefits to the client
NEL responded to unexpected specification changes and delivered a cost –effective measurement system that could operate in non-ideal conditions with minimal intervention.
Use of NEL’s expertise and test facilities allowed the client to move ahead with the development of marginal field in a cost- effective manner.
NEL is a provider of independent consultancy, on-site measurement, testing and calibration, research and development, and training services to the global oil and gas industry. As the holder of the UK’s National Standards for flow measurement, NEL is one of the foremost authorities on flow measurement technology.