Advanced borehole seismic acquisition challenges and successes in large LNG project

Abstract

In this paper we will describe the operational success of largest offshore borehole seismic job which paved the way for several advance borehole seismic projects in Gorgon, Wheat-stone and other projects. The primary objective of the survey was to obtain true vertical time-depth relation and high resolution 2D image below and around the well path for better understanding of reservoir while secondary objective was anisotropy parameters estimation to improve the reprocessing of surface seismic. The followings were the main challenges to this project: Finding a suitable boat/crane for deployment of sources at safe distance from boat hull. Acquisition sequence was switching between different surveys i.e Walkabove and Walka-ways, which made acquisition quite complex. Finding a properly trained navigator for the job. Minimizing rig time Noise attenuation The followings are main conclusions and recommendations VSP modelling was essential for survey design Survey lines were optimized to minimize the rig time Good prejob planning is a key of operation success Poor coupling noise have successfully attenuated during processing Successful acquisition of a comprehensive Walkabove & Walkaways data sets. Combined Walkabove and Walkaway VSPs and Surface Seismic helped to better under-stand the reservoirs. Integration of different data sets multiply the value of each of the elements. Reliable time, depth and velocity information was achieved from Walkabove data set. Recommendations for future acquisition work based on lesson learned on first well.