Summary

This paper describes how permanently installed fiber-optic distributed temperature sensing (DTS) systems were deployed along gravel-packed sand screens in bp’s Azeri field to monitor production from multilayer reservoirs. By directly measuring Joule-Thomson inflow temperatures, the system enables calculation of reservoir layer drawdowns, flow profiles, and pressure changes over time—providing early, nonintrusive production surveillance in wells that cannot be effectively production logged.

What is permanent fiber-optic DTS and how does it enhance production monitoring?

A permanent fiber-optic distributed temperature monitoring system measures temperature continuously along the wellbore using backscattered Raman signals from an optical fiber.

In these completions, the

• fiber is installed outside the sand screen, within the gravel-packed annulus
• measured temperature reflects the inflowing Joule-Thomson temperature before fluids mix inside the basepipe
• temperature changes are directly related to reservoir drawdown and fluid properties.

This configuration allows individual reservoir layers to be identified and monitored in commingled, multilayer wells.

Why is this approach a breakthrough for gravel-packed sand screen completions?

Conventional temperature logs and DTS systems typically measure the axial mixture temperature, which limits layer-level interpretation. Installing the fiber along the sand screens changes what the sensor “sees.”

Key technical advances demonstrated in the paper include

• direct measurement of layer-specific inflow temperaturesresolution of individual reservoir layer drawdowns
• ability to monitor differential depletion over time
• surveillance in wells flowing up to 50,000 BOPD without intervention.

This enables production surveillance where production logging tools are impractical or commercially inefficient.

What value does the system deliver?

Based on field data and modeling results from the Azeri Field, the DTS-based approach enables

• early-time reservoir surveillance immediately after well startup
• layer-by-layer depletion monitoring when fluid properties remain constant
• GOR resolution by reservoir layer when fluid properties change
• flow profile calculation using combined inflow Joule-Thomson and axial temperatures
• lower intervention and HSE exposure via reduced reliance on wireline production logging.

The data provided rapid feedback on reservoir behavior that could not be obtained through conventional logging, supporting improved reservoir understanding and management.

Where was the technology deployed?

The system was deployed in bp’s Azeri Field, offshore Azerbaijan, within the Azeri-Chirag-Gunashli (ACG) development.

Field applications encompassed

• deviated, high-rate oil producers
• multilayer Pereriv B, C, and D reservoirs
• gravel-packed sand screen completions with permanently installed DTS.

The technique was successfully applied to

• monitor reservoir depletion
• identify gas breakthrough in individual layers
• demonstrate sensitivity to future water breakthrough scenarios.

Abstract

bp is developing its Azeri field using deviated gravel-packed sand screen completions producing from the multilayered Pereriv B, C, and D reservoirs. Restricted wellhead access, high rates, and differential depletion of the different reservoir intervals limit conventional production logging possibilities, so bp has chosen to install permanent fiber-optic distributed temperature monitoring systems with its sand screens and to use these systems to monitor production rates and changes over time.

The optic fiber has been installed on the periphery of the sand screen shroud, effectively installing it in the gravel-packed annulus. When the gravel pack is completed, the fiber responds to the reservoir temperature plus the effect of Joule-Thomson warming of the flowing oil caused by the pressure drop (drawdown) in the near-wellbore region. Thermal mixing of the oil with flow from below only occurs once the flow has passed through the sand screen wire-wrap. Thus a direct measure of each individual reservoir drawdown is obtained from the difference between the fiber-measured temperature and the geothermal temperature in the flowing reservoir intervals. Given the reservoir drawdown, the flow rate can then be calculated.

Thus installing the fiber outside the sand screens gives a unique, direct measurement of individual reservoir layer drawdowns, enabling the effects of differential depletion to be monitored over time.

This paper outlines the completion technology used to install the fibers along the sand screens and shows the data and results obtained where reservoirs with different pressures are commingled through gravel-packed sand screens. Thermal models of the near-well environment are described and used to analyze the data and to obtain the flow profile and reservoir layer pressures.

The use of permanently installed fiber-optic distributed temperature monitoring systems on its Azeri reservoir has allowed bp to acquire early time-surveillance data, adding significant value by reducing the voidage risk to the secondary reserves.

Related SLB capability

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