Geodes - 1, Chinese Desert - 0
No failures in the harsh Tarim Basin

There are nicer places than the Taklimaken Desert in western China, but few as important to petroleum production. So that's where the Geode was in May 2002, acting as the workhorse for the China National Petroleum Company (CNPC).

The Geode was needed for a high-resolution refraction statics survey over an area of the Tarim Basin where a 3D-reflection survey had already been conducted. CNPC wanted to gain a better understanding of near-surface velocities, particularly in areas of extreme topography. The Geode velocity measurements would then be used to reprocess the reflection data, with the goal of improving the coherence of deep reflectors.

The survey schedule called for long days for five weeks into mid-June. During that time, the Geode remained on the ground continuously, through pounding rain, scorching heat, and rough handling over extreme topography ― with only the occasional halt when the crew couldn't see because one of the numerous dust storms had blocked out the sun. In all that time, not a single Geode, and not even a single channel, failed.

Six 24-channel modules were spaced at about 250 meters with geophone spacing at 10 meters, or one-fifth of the geophone spacing used in the 3D survey. Over 400 shots using 30 kg of explosives in each shot hole were acquired. The figure below shows the tomographic inversion from the survey.

Field crews scale vertical rock faces to lay cable and plant geophones

Scorching heat and dust storms pounded the crews and the instrumentation. Not a single failure was recorded in the 6-week campaign.

Accurate velocities are critical for processing deep reflection data. Closely spaced shots and tomographic inversion techniques were used by China's Bureau of Geophysical Prospect to improve the quality of their reflection data.

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