Processing and analysis of Vertical Seismic Profile data acquired while drilling (VSP-WD)

Abstract

A Vertical Seismic Profiling While Drilling (VSP-WD) survey method was used to acquire data for processing analysis. This survey carried out in West Cameron in Offshore Louisiana by Schlumberger in 2005. A seismic source was activated in a stable position close to the wellhead, while the three-component receivers were located in the borehole above the drillbit and moving away from the source while drilling. The principal objective of the current thesis is the identification of the Tex X Sand target. Far offset processing analysis of the recorded-memory data has been used to meet this objective. Both a median and an f-k filter have been used for the separation of the upgoing and downgoing waves. The downgoing P wavefield was used to design a deconvolution operator which was applied to the upgoing P wavefield for a waveshaping deconvolution. An exponential gain has been applied for the amplitude recovery. Finally, shifting to two-way time by doubling the first-break time of the upgoing P waves has been completed. The main outputs of the processing were the VSPCDP transformation and the VSP corridor stack. The interpretation was based on the comparison among the corridor stack resulting by this process and those of the process on real-time and recorded-memory data provided by Schlumberger. The very good matching between real-time and recorded-memory corridor stacks and the extension of them deeper to 4000 ms verify that the VSP-WD method can be successfully used for depth uncertainty reduction and look-ahead investigation.