Case Study: Sichuan Geophysical Company Achieves Record Explosives Production in China Seismic Survey

Outstanding, full-offset, full-azimuth explosives operations with UniQ system

Challenge: Complete a seismic survey (to image thin tight oil sands) within a tight time window and project deadline.

Solution: The WesternGeco UniQ integrated point-receiver land seismic system was implemented for full-azimuth seismic acquisition utilizing a dense grid of shallow shot holes with small charge sizes in combination with 45,000 broadband point-receiver sensors and 1-ms sampling.

Result: Record explosives production rates of over 3000 shot points per day were achieved, enabling survey completion on schedule, while meeting imaging objectives.

The Sichuan Geophysical Company (SCGC) was commissioned by Southwest Oil and Gas Company to acquire a high-resolution survey in Sichuan Province in southwest China.

Survey objectives demand a less typical seismic solution

The primary survey objective was a Jurassic tight oil sand reservoir consisting of multiple thin river sand deposits that had proven difficult to image with the low resolution and poor signal-to-noise levels provided by conventional seismic. Other objectives included small-scale fracture imaging on secondary limestone targets.

In addition to the imaging requirements, the project had to be completed within a tight time window so a high-productivity solution was required.

A possible solution was the implementation of high-productivity explosives acquisition; however, this technique requires shallow shot holes in order to minimize the time and cost spent on the drilling operation. Shallow shot holes drilled into the weathering layer lead to increased levels of surface-wave noise (i.e., ‘ground roll’) that conventional seismic systems, which utilize receiver arrays as their primary noise attenuation mechanism, cannot adequately address.

UniQ system delivers superior imaging resolution

The WesternGeco UniQ point-receiver acquisition system was selected. When combined with modeling and adaptive subtraction of surface-wave noise, the UniQ acquisition results in extremely clean seismic data. Thus, the noise generated from the shallow shot holes can be more than adequately suppressed to deliver the desired data quality, without compromising seismic crew productivity.

In order to deliver the required imaging resolution plus the desired level of productivity, the following parameters were implemented.

  • Broadband point-receiver acquisition using 45,000 channels, including 26,000 live channels (another record for seismic acquisition in China)
  • Full-azimuth symmetrically sampled geometry for AVOAZ analysis
  • Explosives acquisition and 1-ms sample interval
  • Dense source and receiver geometry with 13 million trace per km2
  • Small dynamite charge size per hole to generate higher frequencies
  • Shallow shot holes (6 m depth) and small charge sizes (1.0 to 1.5 kg) to enable high-productivity acquisition
  • High precision source and receiver positioning and coordinate-driven processing

Outstanding productivity achieves project objectives

The SCGC UniQ system crew achieved outstanding productivity for an explosives survey, with daily shot rates repeatedly exceeding 3000 shots. The average project production was 2015 shots per day.

The survey completed on schedule and seismic data processing is ongoing at the time of writing. Initial data results are extremely encouraging.

Download: Sichuan Geophysical Company Achieves Record Explosives Production in China Seismic Survey (0.81 MB PDF)

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Daily explosives productionAn SCGC observer operates the UniQ recording instrument.
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