oa Advanced Borehole Seismic Acquisition challenges and Successes in Large LNG Project

In 2011, a large offshore borehole seismic program was acquired in the highly deviated GOR-3B well. It consisted of a Vertical Incidence (Walkabove) VSP and a total of four Walkaway VSP lines, out of which two deep walkaway lines were acquired for anisotropy and two shallow walkaway lines were acquired for imaging. The entire operation took 30 hours. An array of eight Versatile Seismic Imager (VSI) receivers was used as downhole sensors while a three 250 cc airgun cluster was deployed along the side of the UOS Discovery vessel at a safe distance during the entire job thus saving considerable time of changing source locations between different survey types. TRISOR was used as source controller while SWINGS was used as navigation system. Five good shots were stacked within a target circle for each Walkabove VSP station while single shot data was acquired for all four walkaway lines. Real time acquisition support was provided remotely and at the well site to monitor and guide the acquisition. The data quality was good for obtaining high quality time-depth information and for further advanced processing. Quick look processing results were produced within 48 hours followed by advanced processing of the full datasets. Based on the operational and technical success of this project, several advanced borehole seismic projects have been done on successive wells.