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FIBER-OPTIC DOWNHOLE MONITORING SYSTEM  

 

Oil and gas well monitoring solutions based on distributed fiber-optic temperature and acoustic  sensing system use only one fiber-optic cable that is lowered into the well to measure temperature and acoustic noise. Real-time and simultaneous capture of surface parameters enables quick and accurate measurements  made along the entire length of the wellbore. The optimal asset management can be achived with  a combination of temperature, acoustic and pressure sensing employed in the integrated monitoring solution. 



Please refer to the «Solutions» for the system's technical specifications.  


Basic components

Analyzer (surface-mounted panel)
Submersible fiber-optic cable and pressure gauge (optional)
Software

Application

Periodic well surveys
Permanent monitoring

Principle of distributed fiber-optic monitoring 









Electrical signals are converted into light pulses along the optical fiber by laser principle.


The physical medium, which transports optical signals (vibrations) from a light source to the measurement unit, converts light pulses back into electrical signal.


Measurement unit and software is used for analysis and interpretation of changes in light pulse.
Scattering processes in optical fibers:
Raman Scattering – signal amplitude (Anti-stokes component) is temperature dependant.
Brillouin Scattering  – frequency shift is temperature and strain dependant (compression-elongation of the fiber).
Rayleigh Scattering – detection and analysis of instant intensity changes allows detection of acoustic fields and vibrations.


Monitoring of Gas Wells 


Advantages of distributed fiber-optic temperature monitoring:


Maintaining stable gas inflow and flow rate (particularly relevant at late stage of deposits development);
Determination of relative flow rates for each layer/interlayer;
Control technical condition of the well and downhole tools (detection and localization of leaks in casing, packers, etc.);
Detection of water breakthrough and hydrate formation intervals in tubing.


Advantages of pressure monitoring:


Reservoir depletion control;
Reservoir measurement data provides foundation for pressure transient analysis (PTA);
Helps to select optimal operation modes and well intervention activities;
Pressure data can be used for monitoring and historical adaptation of the gas-dynamic models.


Advantages of permanent monitoring:


Detection of liquid dropout caused by differential  heat exchange coefficients  between gas and liquid near the bottomhole perforation intervals (water vapour and gas condensation, reservoir water inflow);
Detection of sand carry-overs and sand plugs intervals (continious monitoring of temperature and acoustic exposures);
Wax deposition computation; helps to select the most appropriate methanol amount to prevent  hydrate formation.


Monitoring  of Gas-Lift Production Wells

Monitoring of downhole relief process in real-time;
Evaluation of well performance;
Timely detection and optimization of potential problems in pressure relief valves.


Monitoring of Injection Wells

Optimization of reservoir pressure maintenance system;
Increased waterflooding efficiency;
Reduced costs of surveys with coiled tubing or downhole tractor;
Regular evaluation of injectivity profile;
Control of well technical condition and downhole equipment;
Workover optimization.

Services provided:
Development of assembly design;
Modelling and calculations aimed to evaluate whether the equipment can be run into the bottom-hole without risk of problems during tripping;
Coordination of work program and tripping operations with the Client;
Engineering supervision of tripping operations and packer equipment pressure testing in the presence of packer manufacturer representative;
Termination of fiber-optic cable prior to installation of cable entry and pressure testing;
Commissioning, carrying our measurements and data interpretation reports.


Monitoring of production wells

Multiple-fractured  production wells (permanent monitoring): Evaluation of inflow profile (to detect producing intervals) after multistage hydraulic fracturing;
Optimization of multiple hydraulic fractures design for efficient well development;
Identification of producing intervals during 2-3 months after multi-stage hydraulic fracturing (MHF), identification of  weak intervals .
Producing wells with ESP: Reservoir management control;
Evaluation of inflow profile (different severance tax imposed on the reservoirs);
Control of well technical condition and downhole equipment;
Enabling Electrical Submersible Pump (ESP) testing in horizontal wells;

Feature of permanent monitoring:

Evaluation of inflow profile (identification of producing intervals) arter multi-stage hydraulic fracturing (MHF) during 2-3 months.
Evaluation of inflow profile in multi-zone reservoirs without production logging tests (PLT). For vertical wells  the difference in geothermal gradient shall not be less than 1.0-1.5ºC);
Detection of water and gas breakthrough intervals, cross-flows and downhole equipment leaks;
Longer life of ESP as a result of controlling both electrical cable and pump  integrity;
Control of of pressure change dynamics to evaluate reservoir parameters.


Production Log Tests  


Evaluation of inflow profile, waterflooding and technical condition with fiber-optic systems using  different methods of optical signal detection:

- Raman scattering;

- Brillouin scattering;

- Rayleigh scattering.


Integrated solutions (distributed fiber-optic temperature, acoustic and pressure monitoring system) 

Repetitive seismic measurements in wells with acoustic monitoring;
Hydralic fracturing process monitoring using temperature, pressure and acoustic sensing;
Permanent measurement of inflow profile using temperature, pressure and acoustic sensing.

                                          

Value add through effective use of information;
Timely decision making and problem-solving;
Efficient planning of well interventions (field geophysical tests, major workover);
Reduced production cost;
Increased recovery index.




 

Monitoring of oil & gas gathering systems

Fiber-optic monitoring offers a vast variety of applications from controlling  technical condition of oil & gas gathering systems through  to permanent monitoring of::

Injection and horizontal wells;
Multiple-fractured vertical and horizontal wells;
Steam-injection wells;
Gas wells.
Up to 20 fiber-optic cables can be monitored with single analyzer;

Up to 80 km sensing range with single temperature analyzer;

Up to 40 km sensing range with single acoustic analyzer.





"Use of fiber-optic technologies allow the well owners to control asset condition from the bottom-hole through the trunk pipeline” 



Oil gathering system Well pad 

 

 

   

 

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