FEATURES OF ANOMALIES RELATED TO RESERVOIR AND ANOMALY PATTERN RECOGNITION IN INTENSIVE OIL AND GAS GEOCHEMICAL EXPLORATION

Intensive oil and gas geochemical exploration is a new technique recently developed by former Hefei Institute of Petroleum Geochemical Exploration.Based on the research results of the near-surface hydrocarbon compositions and their distribution characteristics acquiring through the new lighthydrocarbon detection method,the high-density sampling grid and the unconventional data-processing methods,this technique can evaluate the oil potential of a trap or the favorable areas of oil and gas accumulation.The hydrocarbon anomaly related to reservoir recognized by intensive geochemical exploration normally occurs as apical anomaly being composed of the combination of block anomaly and halo anomaly.The fabric of the light hydrocarbons is characterized by heavy inside and light outside an existing oilfield.The concentration center of the hydrocarbons,especially the heavy hydrocarbons,coincides well with deep oil and gas accumulation.In order to further improve the ability of the oil and gas geochemical exploration technique to resolve the complicated geological problems,it is proposed that,during intensive geochemical exploration,anomaly rings should be cautiously delineated while researches on anomaly characteristics should be paid more attention to.Evaluation techniques like multi-parameter geophysical and geochemical recognition,fractal theory and neural network should be used in predicting oil and gas potential.The favorable site predicted by using the 3-layer BP neural network technique to recognize the geochemical anomal patterns in HBG oilfield has been verified by the consequent drillings.This result shows that in the recognition and the evaluation of the geochemical anomaly related to reservoir,integrating hydrocarbon concentration anomaly and pattern recognition technique is feasible and effective for oil and gas potential prediction.