Abstract: The concentrations of some fluid compositions such as He, Ar, CO₂ and CH₄ in the mud of CCSD main well at depths between 100 and 2045m are collected and analyzed in this paper. To study the relationship between the anomalous variations of fluids and seismic activities within the focus area, the authors have obtained and compiled seismic catalogues with magnitude over 1.0 in the period of July 1, 2002~April 30, 2002. The concentrations of these fluid components (He, Ar, CO₂ and CH₄) are analyzed and processed using the daily statistics, the calculus of difference and the maximum coefficient of correlation of CO₂-CH₄. It is indicated from these results that the anomalous variation occurs before or after seismic activity. From the features of some fluid composition in the CCSD main well and the seismic activity at CCSD site within the radius if 500 km, it can be concluded that the features of fluids in the main well were possibly responsible for seismic activity.

Key words: Fluid, Geochemistry, Seismic activity, CCSD main well