Virtual-Measurement Value During Startup of Major Offshore Projects

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper IPTC 14518, ’Virtual-Measurement Value During Startup of Major Offshore Projects,’ by R. Cramer, SPE, N. Griffiths, P. Kinghorn, SPE, and D. Schotanus, Shell Global Solutions; John Brutz, SPE, Shell USA; and Klaus Mueller, SPE, Shell Oman, prepared for the 2011 International Petroleum Technology Conference, Bangkok, Thailand, rescheduled to 7-9 February 2012. The paper has not been peer reviewed. How can wells be managed optimally if one does not know continuously what they are producing? This problem is more critical at initial startup of the wells. Shell uses a real-time well virtual-flow-measurement tool, running on 60% of Shell’s global production, which has enabled significant added value in the areas of real-time surveillance and optimization. The virtual-flow-measurement tool has been applied in the startup of several of Shell’s offshore projects in the Arabian Gulf and in the Gulf of Mexico. Introduction Shell has several large upstream offshore projects in various stages of startup or commissioning. These projects have large capital investments and reserves contribution and a high degree of difficulty (e.g., very deep water, subsea processing, long subsea multiphase pipelines, and feeding large onshore gas plants). Hence, it is imperative to start up the processes as quickly and efficiently as possible, yet maintain the highest possible standards of technical integrity, safety, and environmental effects. Key aspects for efficient and effective project startup are well and reservoir surveillance and hydrocarbon accounting. It is important to know how much the wells are producing and the composition of the fluid streams to maximize production and for flow assurance, asset technical integrity, and accounting purposes. Ideally, this would be achieved by use of multiphase flowmeters (MFMs) on each well to measure the oil, gas, and water flows physically and continuously, or by routing each well progressively to a test separator as the wells are started up. However, at the time of startup, MFMs may not have been installed for all wells, and for wells that do have them, they usually are not yet commissioned because MFM commissioning requires fluid samples from the wells, and for subsea wells, sampling usually is performed robotically and at a later stage of startup. Virtual flow meters (VFMs) can be operational when production begins. Similarly, test separators may not be commissioned at the time of initial well production, and if they are operational, they are not suitable for tracking production from multiple wells. Hence, virtual flow measurement has significant value for well/reservoir surveillance and hydrocarbon accounting from initiation of startup to the time when MFMs are effectively commissioned and, thereafter, as effective insurance in case of individual-meter failure.