Abstract
Most conventional soil-gas methods use instantaneous samples, in which the sample collected represents the soil-gas composition at the moment of collection. Short-term meteorological influences may yield noisy data. The K-V Fingerprint Technique couples time-integrated soil-gas collection with mass-spectrometric analysis and pattern recognition, and thus overcomes the problems inherent in most other gas geochemical methods.
Three surveys using the K-V Fingerprint Technique have been conducted in the Minami-Aga Oil Field Case Study (Niigata Prefecture, Japan) in 1986, 1987, and 1988. The results of the three surveys show an apical geochemical anomaly over the same area of the Minami-Aga Oil Field every year. The factor spectrum derived from factor analysis of the mass spectra shows that light aromatic hydrocarbons are responsible for the geochemical anomalies.
Furthermore, a few samples collected over the known producing area and samples of vapor-phase compounds present in equilibrium with some crude-oil samples were analyzed by GC-MS to verify the compositional relationship between surface soil gases and the oil in the reservoir.
Based on those analyzed data, it was concluded that hydrocarbon gases from the reservoir at 2, 300 meters reach the surface in less than 20 years.
