Evolution in Optical Downhole Multiphase Flow Measurement: Experience Translates into Enhanced Design

Abstract

Innovative technology and measurement methods along with intelligent production optimization processes are important enablers with regards to intelligent fields and real-time reservoir management. Downhole multiphase flow measurement technologies play a major role in monitoring and optimizing well performance especially wells equipped with advanced well completions such as downhole inflow control devices (ICD) or inflow control valves (ICV). This paper builds on a pilot installation and comprehensive assessment of the world's first installation of downhole multiphase flowmeters and optical pressure and temperature sensors in a maximum reservoir contact (MRC) well in Saudi Arabia. One of the major findings from the initial study was that while the optical flowmeter operated successfully at most downhole choke valve settings, it was unable to make sensible readings at specific settings due to excessive acoustic noise. The results from the assessment were instrumental in improving the design of the flowmeter to tolerate higher acoustic noise levels. The initial appraisal and acceptance of this completion technology was closed by having the improved flowmeter manufactured and successfully flow tested under various laboratory conditions. The lessons learned from this experience have provided insights into downhole multiphase flowmeter sensing technologies, its capabilities and limitations. Furthermore, it demonstrates how open collaboration between operator and equipment manufacturer can yield reliable and fit for purpose equipment, a model that can be used to improve other technologies pertaining to intelligent fields and real-time reservoir management. BackgroundProduction optimization efforts have been the subject of a number of studies in the past within Aramco (Al-Bani et al. 2007;Arnaout et al. 2008;Mubarak et al. 2007Mubarak et al. , 2008. The current work builds on the previous work the subject of which was the performance evaluation of a permanent downhole monitoring system (PDMS).The PDMS was installed in world's first MRC and trilateral smart well in 2006. The three laterals were equipped with ICVs and PDMS comprising three 2-phase optical flowmeters integrated with pressure and temperature (P/T) gauges. The well was completed with 7" tubing and a deepset downhole sub-surface safety valve (SSSV) to accommodate future tubing electric submersible pump (ESP) installation. The ICVs, optical flowmeters and P/T gauges were located slightly up-hole from each lateral as shown in Fig.1.The PDMS has been designed with the philosophy of having low complexity and passive components downhole while keeping active electronic equipment on the surface to ensure high reliability and measurement accuracy. The 2-phase flowmeter and optical P/T gauge were built as a single integrated assembly (Fig. 2). The meter is full bore, non-intrusive, has no exposed sensors, moving parts or downhole electronics and has high resilience to erosion and corrosion. The PDMS system provides the production parameters required to determine the o...

Flow Characterisation Using Fibre Bragg Gratings and Their Potential Use in Nuclear Thermal Hydraulics Experiments

“…where dr is the change in the pipe radius (m), dP is the change in the radially acting pressure (Pa), r is the pipe radius (m), E is Young's modulus of the pipe (Pa), and t is the time over which the pressure changes (s) [53].…”

“…If multiple optical fibres are wrapped around the outside of a pipe at a known distance from each other, then the speed of sound and flow rate can be calculated based on the time difference between the FBGs of each fibre coil detecting the pipe diameter expansion. It should be noted that this expansion is a combination of effects arising from both pressure wave propagation and turbulent eddies acting against the pipe walls [53]. For the application, where flows impose rapidly varying dynamic strains on a pipe, low-reflectivity FBGs interrogated through interferometric techniques are commonly used due to the high resolution and sensitivity this method provides [52].…”

“…Optical flowmeters of this type have been extensively utilised in the oil and gas industry to analyse multiphase flows, including the in-well instrumentation measuring flow rate, direction and void fraction, and have been commercialised [53][54][55][56]. However, as discussed in Sections 3 and 4.1, no example of this technology being utilised in nuclear thermal hydraulic experiments has been identified.…”