Real-Time Composition Measurement for Fiscal, Allocation and Process Optimization

Abstract

Abstract The global oil industry has a large installed base of mature offshore platforms and facilities, often with declining production. A trend is to use this infrastructure to produce and process new discoveries, reducing time to production and recovery costs while extending infrastructure operating life. However, production of new oil fields using existing infrastructure presents unique technical challenges. Accurate, repeatable and reliable measurement of produced oil and water is vital for fiscal, allocation or royalty purposes, as well as automation and control. This challenging measurement requires high-energy mixing with low power consumption and negligible pressure loss in a very small footprint. The measurement uncertainty of net oil (oil minus water) for fiscal and allocation purposes is defined by international standards and contracts. With the increase in the use of declining facilities, a new technical challenge has emerged. To be able to accurately allocate the new fluids to the field, partner or different tax regimes they must be measured to fiscal accuracy prior to being mingled with other fluids for processing. Oil and water measurements are often performed at the output of first stage separation. This creates a challenge, as the fluids are close to the critical pressure, meaning that any pressure drop potentially results in cavitation. In addition, production pipelines are generally less than 8 inches, so any obstruction causes an undesired pressure loss or restriction. These requirements highlighted the need for an effective, nonintrusive mixing device to enable operators to accurately measure and control the new fields being developed with today's greater capital constraints. Research was conducted, as part of a Joint Industry Project, at Imperial College in London followed by extensive computation fluid dynamics modeling to develop a conceptual design. The design was independently tested at the National Engineering Laboratory at East Kilbride, UK. The test independently verified that the design met the uncertainty performance criteria of the international API and ISO sampling standards across the wide range of water cut seen in both mature and new production. Once verified, the design was scaled for operating line sizes seen in the targeted application, and early deployment sites were identified. The paper discusses the application envelope identified by offshore operators and the technical challenges they were seeking to solve. It follows the design process, highlighting the choices made and the results and methodology used in the independent testing to verify performance.