Confined groundwater pollution mechanism and vulnerability assessment in oilfields, North China

The confined groundwater in North China oilfield is contaminated by oil and oilfield gas. Based upon the analysis of the geological structures and hydrogeology of the study area, the pollution mechanism of the confined groundwater is studied. The main influencing factors are the oil-gas deposit size, the distribution of faults, oil exploitation well distribution, water input well distribution, aquifer media permeability, etc. The vulnerability assessment model is established for the confined groundwater in the study area, and the artificial neural networks (ANN) assessment method is adopted in this paper. The assessment results of the confined groundwater vulnerability fits well with the actual situations in the study area, which indicates the ANN assessment method is correct, accurate and objective.