Passive Sea-Bottom Observations

 

1. The GNS™ Autonomous Self Pop-up Nodes (SPNs) provide the most cost-effective and mobile solution for monitoring of hydrocarbon reservoirs

 

Operational Advantages

  • Fast and easy multi-node array deployment, recovery, data reading and re-deployment of instruments to the sea bottom for further recording. The SPN sea-bottom position can be controlled with the acoustic channel or with low-power airgun data. The positioning control of horizontal components is provided by active source data, or by boreholes perforation shots.
  • The SPNs can be deployed near and even under surface obstacles; the subsea deployment over a production field provides reduced weather- and sea-induced noise.

 

Problems to be solved with passive seismic observations at the production oil fields:

  • Micro-seismic monitoring of hydro-fracturing;
  • Time-lapse seismic monitoring of gas-oil contacts;
  • Detection and monitoring of active faults;
  • As a supplement to active 4D observations;
  • Active 4D surveillance is carried out with greater time intervals, the time gaps between active observations can be filled out by passive monitoring;
  • Monitoring of changes generated by production effects, for example, consolidation or subsidence of production layers, etc.

2. The GNS™ SPNs is ideally suited to acquire data that can be used to derive fluid indicators or direct hydrocarbon indicators. This fast-growing reservoir technology is looking for narrowband acoustic reflection within 1 to 6 Hz range, linking it to the possible hydrocarbon prospects. The observations for each position last not more than one 24 hours; then the instruments must be quickly re-deployed to cover the largest possible area by the measurements. The SPNs can be equipped with compact and light low-frequency seismometers designed by Moscow Institute of Physics and Technology (MIPT).

 

Technical characteristics of low-frequency seismic detectors

 

Standard frequency bandpass 1 - 50 Hz
Conversion factor 250 V/(m/s) – non-differentiated output
Maximum output level ± 7.5 V
Integrated noise in operating band 15 nm/sec
Dynamic range 122 dB
Power supply 12 V DC / 15 m
Operating temperature range -12 .. +55 ° C (-40 .. +55 ° C - option)
Tolerated installation angle  ± 15°
Dimensions  D=70mm h=93mm
Housing material Aluminum
Weight 800 g

 

Three-component low-frequency detector attached to the self pop-up recorder housing