Logging While Drilling (LWD) seismic technology has been around for the past decade.

With the evolution of the technology comes an evolution in the service for delivering valuable answer products at the right time.

This paper address the key components of seismic while drilling as well as answer products from seismic checkshots through to re-migrated surface seismic volumes of interest in drilling time.

The case study for seismic while drilling comes from offshore Vietnam where two successive Exploration wells were drilled. The seismic while drilling was identified as a key technology for each well.

The LWD seismic known as seismic VISION* was run for geostopping decisions to set the 9 5/8 inch casing at the correct point immediately above a carbonate reservoir.

This would then allow drilling the ensuing 8 ½ inch hole section with the appropriate mud weight to reduce the risk of a kick/loss scenario.

In both instances the depth uncertainty of the surface seismic was +/-50m although the final completions design for the final hole section in 8 ½ inch hole was based on a +/- 20m tolerance.

Hence getting accurate depth predictions ahead of the bit was vitally important. For the actual operation the depth accuracy achieved was within 15m of the actual carbonate top without actually penetrating it for both wells. This allowed for successful well construction each time.

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