Abstract

Real-time, downhole, multiphase flow rate data is widely acknowledged to be of significant value for production optimization. This is particularly the case for high-cost deepwater developments and in complex multi-lateral wells. Applications of downhole flow data include zonal production allocation, identifying and localizing production anomalies, direct determination of well productivity index, ability to commingle production from multiple zones, and reduction in surface well testing and facilities requirements. However, despite the potential value of this data, in the past reliable continuous measurements of downhole flow rates in producing wells have not generally been available because of difficulties in designing and deploying measurement devices for hostile in-well environments.

This paper discusses the design, operating principles, and flow loop testing of the world's first all-fiber optic multiphase flowmeter for downhole deployment. The flowmeter provides real-time measurement of flow rate, phase fraction, pressure and temperature. It is deployed with the production tubing and is rated to 125°C and 15,000 psi. It is full-bore, non-intrusive, has no moving parts, is electrically passive, and overcomes the design limitations imposed by downhole environments. Thus, it has the potential for providing highly reliable downhole measurements. The flowmeter has been extensively tested in Shell's multiphase flow loop in Rijswijk, The Netherlands over a wide range of oil and brine compositions and phase fractions, flow rates, and meter inclinations. Results from the testing have demonstrated the ability of the flowmeter to measure flow rates and water fractions in oil-water systems to within 5% over the entire range of water cuts. These results have been validated by data from several field deployments.

Introduction

Over the past five years, there has been a significant increase in installations and applications of permanent, in-well monitoring systems. This has been especially true in high cost, complex completions such as multilateral and deepwater wells. Traditionally, permanent monitoring has primarily referred to downhole pressure and temperature measurement. Recently, however, the development and deployment of accurate and reliable downhole flowmeters has extended the types of in-well measurements available to fluid flow rates and phase fractions.

Production and reservoir engineers have appreciated the value of real-time, continuous downhole flow rate information for years. Applications for downhole flow data are numerous.

Zonal production allocation.

In multi-zone completions, data from a downhole flowmeter can be used to allocate production from individual zones. This can be achieved either with a flowmeter placed above each producing zone or by installing meters between each zone and using total flow measured at the surface to obtain the contribution of the uppermost zone.

Identify and localize production anomalies.

One or more downhole flowmeters placed in the lateral section of a horizontal well can help locate production anomalies, such as which part of the lateral is contributing to flow and where water or gas breakthrough has occurred. This allows localized well stimulation or other well treatments to be performed to increase well productivity.

Direct determination of productivity index.

Real-time downhole flow rate and pressure data allows determination of a well's productivity index at any time without need for intervention.

Commingled production.

Reliable downhole flow data allows for the potential to commingle production from multiple zones.

Reduce surface well tests.

Real-time downhole flow data reduces the need for surface well tests to determine the productivity of individual wells.

Reduce surface facilities.

The ability to measure flow rates downhole may eliminate the need for a surface test separator, thereby significantly reducing the facilities requirements on offshore platforms.

Zonal production allocation.

In multi-zone completions, data from a downhole flowmeter can be used to allocate production from individual zones. This can be achieved either with a flowmeter placed above each producing zone or by installing meters between each zone and using total flow measured at the surface to obtain the contribution of the uppermost zone.

Identify and localize production anomalies.

One or more downhole flowmeters placed in the lateral section of a horizontal well can help locate production anomalies, such as which part of the lateral is contributing to flow and where water or gas breakthrough has occurred. This allows localized well stimulation or other well treatments to be performed to increase well productivity.

Direct determination of productivity index.

Real-time downhole flow rate and pressure data allows determination of a well's productivity index at any time without need for intervention.

Commingled production.

Reliable downhole flow data allows for the potential to commingle production from multiple zones.

Reduce surface well tests.

Real-time downhole flow data reduces the need for surface well tests to determine the productivity of individual wells.

Reduce surface facilities.

The ability to measure flow rates downhole may eliminate the need for a surface test separator, thereby significantly reducing the facilities requirements on offshore platforms.

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