The feasibility and value of low-frequency data collected using colocated 2-Hz and 10-Hz geophones

Abstract

ConocoPhillips acquired a production 3D surface seismic survey in 2010. The survey size was about 410 square miles recorded by 10-Hz geophones with INOVA 364 vibrators that are capable of sweeping from 1 to 150 Hz. In addition, we carried out a field experiment recording a swath of 3D surface seismic data with colocated 2-Hz and 10-Hz geophones. The cost of acquiring the 2-Hz geophone data was negligible when compared with the cost of the entire 3D survey. Because the vibrators can produce energy down to 2 Hz, the use of the 2-Hz geophone is crucial in capturing this energy. To our knowledge, this was the first field experiment employing the 2-Hz geophones and vibrators that could transmit enough low-frequency signals into the ground. The questions we investigate in this field experiment are: (1) how much low-frequency signal can be recorded using 2-Hz geophones, (2) how much degradation of low-frequency signal results from the 10-Hz geophones when compared to the 2-Hz geophones, and (3) the possibility of using the colocated data sets to enhance the low-frequency signal of 10-Hz geophone data that include both experimental and production data. The analyses of the 10-Hz and 2-Hz geophone data in prestack and poststack domains concluded that 2-Hz geophone data clearly exhibited more low-frequency signal than the 10-Hz geophone data. The 2-Hz geophone stack had low-frequency signal down to 2 Hz, and a spiking deconvolution further extended the amplitude spectrum down to 1 Hz. In addition, we develop a novel technique to derive a deterministic match filter from the colocated data sets. The application of this filter on the 10-Hz geophone data recovers the low-frequency signal below 10 Hz.