Distributed Acoustic Sensing Interrogator Oil Gas CCS | SLB

Optiq distributed acoustic sensing interrogator

Compact, low-power unit handles long fiber lengths with high detection sensitivity and low false-alarm rate

Optiq SLB fiber-optic solutions

How it improves performance

A component of SLB Optiq™ fiber-optic solutions, the distributed acoustic sensing (DAS) interrogator features high sensitivity and dynamic range. These characteristics are key enablers of several fiber-optic well monitoring applications.


Multiphase production flow profiling in wells with low gas fraction and in high-rate wells

Oil or water inflows usually produce less vibration than gas. Consequently, instruments with high DAS sensitivity are essential for quantifying these inflows and differentiating phase fractions from noise.

Conversely, in high-rate wells, especially gas producers with ICDs or wells undergoing hydraulic fracturing, the high noise signal can saturate the DAS response and challenge inflow or outflow profiling. The wide dynamic range of the fiber-optic DAS interrogator ensures acquisition of high-quality data for more accurate interpretation of zonal flows.

Transient analysis requires changing the drawdown, and the interrogator’s high sensitivity enables reducing the amplitude of the change to minimize unwelcome production losses while preserving data quality. The small spatial sampling interval enables higher-resolution data interpretation along the wellbore and is critically important for distinguishing flow-related features from other acoustic data.


Injectivity profiling

Injection produces small vibrations (acoustic signals), which are mostly associated with water flowing out to the formation behind the casing. Even more challenging conditions are encountered postinjection—during warmback—with low wellbore afterflow or crossflow rates, which generate low-amplitude vibrations. High DAS sensitivity and dynamic range address these challenges.


Well and caprock integrity determination

Leak detection to remedy well integrity issues often requires the ability to detect weak vibrations and accurately locate them along the wellbore.

For monitoring caprock integrity and OOZI, the analysis is based on quantitative interpretation of DAS signal variations in the vicinity of the unintended fracture initiation point. High DAS sensitivity is extremely important for improving the accuracy of locating the initiation point and estimating fracture parameters. The interrogator’s dynamic range ensures reliable detection of fractures and OOZI, enabling greater injection volumes without risking caprock damage.


Seismic data acquisition

Optiq Seismic™ fiber-optic borehole seismic solution enables acquisition of zero-offset, walkaway, and many more types of vertical seismic profiles (VSPs); 3D seismic surveys; and 4D seismic surveys for reservoir monitoring in minutes rather than the hours or days required using conventional methods.

How it handles extended lengths of fibers

The distributed fiber-optic sensor interrogator unit contains two optical modules, which can simultaneously interrogate sensing fibers, each up to 65 km long. As a result, the unit has a 130-km range, making it ideal for pipeline integrity monitoring. For subsea applications, where the sensing fiber can be longer, a subsea optical amplifier can extend the interrogator's range.