A New Mapping Method to Assess Aquifers Vulnerability Based on Hydrogeological and Seismic Data-Case Study: Mio-Pliocene Aquifer in Hassi Messaoud-Algeria

摘要

Non renewable groundwater resources in some arid regions are the unique source of water and constitute strategic reserves for more than ever with the expected water shortage in the near future. Thus, contamination due to the infiltration of pollutants coming from oil and gas industries is one of the major risks that are jeopardizing these valuable resources. The main purpose of this paper is to present the widespread aquifers vulnerability evaluation methods prior to introduce and discuss the new mapping method we propose for oil and gas upstream activities. The rationale for this mapping method is linked to time of travel and the quantity of contaminants that move from the surface to the aquifer. Three key parameters are considered: 1. Consolidation of the upper geologic layers in the unsaturated zone (C); 2. Depth to water table (D); 3. Aquifer Media (A). On one hand, seismic data have been used to estimate the consolidation of the unsaturated (vadose) zone. On the other hand, hydrogeological data from almost a hundred water wells in Hassi Messaoud field in Algeria have been used to determine the hydraulic head, the static level and the local underground flow of the mio-pliocene water table. Therefore, processed data were used for the purpose of drawing the vulnerability maps allowing a better understanding and assessment of the aquifer sensitivity to potential pollution. This simple yet useful method is developed to be used as a decision making tool when dealing with groundwater protection in oil and gas activities.