Subsea-Data Management

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 18744, "Subsea-Data Management," by Brian Drakeley, SPE, Weatherford International, Svein Omdal, SPE, Statoil, and Sigurd Moe, SPE, FMC Technologies, prepared for the 2007 Offshore Technology Conference, Houston, 30 April–3 May. This project will contribute toward making real-time reservoir-monitoring and other downhole data avail-able every where on Statoil's network infrastructure. The goal is to resolve hurdles for implementing fiber-optic monitoring and data transmission from subsea developments. Focus is on detailed seabed-system solutions to create an open high-speed communication infrastructure, which fiber-optic technology enables. The project will develop interfaces with existing subsea systems that have only electrical low-bandwidth communication systems. Introduction In June 2005, Statoil requested technical and commercial proposals relating to the development of integrated fiber-optic systems (an integrated subsea communications system) and reliable downhole sensors. There are two key project areas:Downhole-sensor (DHS) sand monitoring (identification and quantification), multiphase flowmeter (for intelligent-well applications), and distributed pressure and temperature measurementsIntegrated fiber-optic subsea system (IFOSS) containing subsea well-sensor interrogation solutions, a subsea-control system, a subsea telecommunication and transmission system, and an integrated fiber-optic system Fig. 1 illustrates the scope of the project and how these key project areas fit into the total integrated system. DHS Real-Time Reservoir Monitoring Essentially, in-well monitoring systems are required that deliver high-quality measurements throughout the life of the well without the need for routine maintenance or intervention. With no downhole electronics in existing fiber-optic systems, sensing systems are intrinsically more reliable than electronics-based systems. With increased demand for more data on reservoir and well performance, communication systems must have that significantly improved signal performance, data density, and trans-mission distance, which leads to a fiber-optic solution. Existing Downhole Fiber-Optic Sensors Currently, there are four types of optical sensing systems. Pressure/Temperature (P/T). Many P/T fiber-optic gauges have been installed and are very reliable. Distributed Temperature Sensing (DTS). DTS systems are the most widely used fiber-optic sensing system. These systems provide a continuous temperature log of the well along the entire length of the fiber [e.g., a production (or injection) thermal profile of the well] and can be used to identify well problems; water, gas, and steam breakthrough; gas lift valve and system performance monitoring; and paraffin and hydrate formation monitoring. Measurement points are at 1-m intervals, and temperature resolution can be on the order of ±0.1°C.