Gas in Soil. I: Detection and η‐Profiling

Abstract

Increasing offshore construction activities in areas where marine sediments contain gas (either in dissolved or free form) have generated an interest in developing in situ test equipment capable of detecting and quantifying the amount of in situ gases (η‐profiling). This is important since: (1) Failure to detect gas pockets ahead of the drill bit during soil investigation or drilling operations may result in gas blowouts, and, consequently, life and financial losses; and (2) if the amount of gas is not correctly quantified for use in advanced laboratory testing of gassy soil specimens, misleading design parameters may be established. This paper introduces a new in situ test device, referred to as the BAT probe, which is used to sample in situ pore water/gas to quantify the amount of gas in the soil (η‐profiling) and to predict the presence of gas pockets ahead of the drill bit. The results from a laboratory verification test program and several offshore soil investigation projects are presented and discussed.