Look Ahead Rig Source Vertical Seismic Profile (VSP) Applications - Case Studies

Abstract

Borehole Seismic has played vital role in aiding the better understandings of the conventional and unconventional reservoirs around the world in the last few decades. In VSP technique we have an advantage of listening and measuring the formation velocities at seismic scale in the vicinity of the formations while on contrary in surface seismic measurements, it is done from surface. In vertical seismic profile (VSP) technique, the direct arrivals are recorded in addition to the reflections below current sensor depth, which makes it feasible to use the reflections to predict ahead of current depth, detailed methodology will be discussed in the paper. In this paper, we will discuss a case history where look-ahead VSP have been successfully employed by reducing the pre-drill depth uncertainty of reservoirs from tens of meters to within a meter. Schlumberger's down-hole seismic tool was used to acquire intermediate look-ahead VSP. The data was acquired in open hole, few hundred meters above the target intervals. Fast-track processing of the field data and timely delivery of a high quality product allowed a rapid interpretation, which resulted in significant savings in relatively high cost offshore environment.