Schlumberger

Technical Paper: Seismic Measurements While Drilling Reduce Uncertainty in the Deepwater Gulf of Mexico

Society: SEG
Paper Number: 1851248
Presentation Date: 2004
 

Abstract

Seismic uncertainty in the deepwater Gulf of Mexico impacts the efficiency of well construction and thus has a direct effect on the overall cost of a project. Any advances in technology that can reduce uncertainties and reduce risk have a significant impact on the ability to drill these wells safely and effectively.

A new tool that acquires seismic checkshots while drilling now makes it possible to place the bit on the surface time section, enabling depth-based decisions, such as casing point selection, to be made with increased certainty. Furthermore, the interval velocities derived from successive checkshots can be used to calibrate logging-while-drilling (LWD) sonic data and generate synthetic seismograms. At the end of the run memory data are recovered from the tool and the 4C waveform data are used for transit time quality control and to generate vertical seismic profile (VSP) images that can be tied to the surface seismic and sonic-derived seismograms.

In this paper we present a case study describing the use of this technology in the ultradeepwater Gulf of Mexico, where checkshots acquired while drilling, transparently to normal drilling operations, were used to provide real-time depth predictions to the drillers. Analysis of the recorded data showed a good match to the surface seismic and significant look-ahead capability.