Abstract:

In order to develop and enrich the qualitative identification and quantitative interpretation methods in gas hydrate investigation, a new method for gas hydrate saturation estimation using chloride concentration from well logging interpretation was studied and applied with field data. The experimental result on chloride concentration, along with the log response of the gas reservoir in certain area in South China Sea, show the well-known close relationship between gas hydrate content and pore water’s chloride concentration. Chloride concentration of pore water was calculated through porosity and resistivity logs, and gas hydrate content was estimated from it consequently. For the purpose of improving the accuracy and reliability of this method, a regression formula for porosity interpretation was built up, the parameters of m and a in Archie formula were estimated, and the background value of chloride concentration correspond to the target zone was defined by filtering and interpolation. The preliminary application show that the method for gas hydrate content estimation by using of chloride concentration from log interpretation can work as expected and the estimated gas hydrate content can match the experimental result approximately both in their mean values and distribution ranges.

Key words: gas hydrates, saturation, chloride concentration, well logging