Characterising fluid movement within the well can be the key to understanding and optimising well performance; Silixa’s intelligent Distributed Acoustic (iDAS™) and Distributed Temperature Sensors (ULTIMA™ DTS) offer a means to efficiently gather production or injection profiles along the entire wellbore with minimal or no intervention.
Distributed sensing utilises optical fibres within a steel walled cable which can be placed permanently in the well as part of a completion or temporarily during intervention. The optical fibre behaves as a sensor array making it possible to log the entire well path continuously without the need to move the cable and so providing information about dynamic flowing conditions in a way in which conventional sensors cannot.
Temperature data has been used in the evaluation of producing wells for many years and is still a core measurement for the production engineer however complimenting temperature information with the unique attributes of true acoustic data gives the user a much more powerful decision support tool.
Downhole acoustic and temperature data can be used qualitatively to quickly identify which zones are actively producing (or taking fluid) or to determine the relative contribution of each zone using algorithms which harness temperature and the content of the acoustic signal.
Advanced acoustic processing, unique to Silixa, can be used to determine the speed of sound in the production fluid at different depths; this information indicates in-situ fluid type and can be used to resolve hold-up in two-phase flow. Additionally the Doppler shift between the speed of sound modes travelling up and down in the well make it possible to measure the fluid flow velocity and hence flow rates for a given tubing size.
Field software allows for real-time integrated visualisation of temperature and spectral acoustic data for quality control and initial evaluation while a post processing platform facilitates advanced data processing and versatile plotting options so that corroborating answers from independent measurements, iDAS™ and ULTIMA™ DTS, can be presented as actionable information to the user.
Downhole monitoring results can be further calibrated by the inclusion of an iDAS enabled flow meter installed on surface flow-lines.
The iDAS and ULTIMA DTS can be deployed periodically to gather discrete production profiles using existing optical fibre installations or by running a fibre optic cable in-well as a cable or coil tubing intervention. Alternatively the systems can be installed as part of a permanent monitoring solution providing continuous production information and conditional status alerts incorporated into a SCADA or similar system.
Silixa offers a range of fibre optic cables optimised for iDAS and DTS measurements along with permanent fibre optic cable installation equipment and procedures to ensure a safe, efficient and long lasting monitoring solution.
- Intervention-free production data acquisition
- Inherently reliable downhole sensor array
- Continuous depth and time monitoring better describes changing production patterns
- Production information without disturbing the flow path
- Supporting answers from multiple measurements improves decision confidence
- Production monitoring enables timely decisions on remediation
- Data acquisition on either singlemode or multimode optical fibre cable
The animation above shows a composite presentation of Silixa distributed temperature and acoustic data for the purpose of production profiling. Depth base distributed data is plotted alongside imported well information and is processed and presented according to a user selected time window; in this case each frame represents three minutes of data. In this example a basic data presentation has been used to identify regions of inflow using iDAS data to aid what would otherwise be a difficult interpretation of temperature data alone. Similar data presentations can include zonal contribution and fluid typing outputs based on iDAS and DTS processing methods offering high confidence corroborated answers.
- Identify active vs. inactive production zones
- Zonal production allocation
- Cross-flow identification
- Water or Gas entry detection
- Injection profiling
- Flow regime identification
- Production diagnostics
iDAS captures the true acoustic field (amplitude, frequency, and phase) at all points along the well. Silixa’s advanced data processing techniques include conversion to the space-frequency domain (k- ω) allowing individual speed of sound components to be identified, including those travelling within the well fluid both in an uphole and downhole direction (above left).
The speed of sound in a production or injection fluid contains valuable information about the fluid composition and also allows the flow velocity to be determined from the Doppler shift between up-going and down-going sound (above right).
The ability to extract this information from acoustic data along the entire instrumented well path signals a new era in well performance monitoring.