Effect of hydraulic fracturing of shale gas reservoirs on groundwater in Algeria

The exploration of shale gas reservoirs in Algeria has led to significant debate in the oil and gas sector due to potential risks to the country's declining water resources.This study focuses on assessing the risk of groundwater contamination from hydraulic fracturing (HF) in the Algerian southeast region, where the Frasnian shale gas reservoir lies between 3575 m and 3720 m deep, and the nearest aquifer Lias Horizon B is located at 1572 m.A model was developed using MODFLOW software, incorporating the characteristics of the geological layers traversed by well P-1, recently drilled in the region.A hypothetical, homogeneous, and continuous permeable pathway connecting the top of the Frasnian reservoir to the Lias Horizon B aquifer was included in the model.The study is based on simulating a reference scenario to which values observed in the region were assigned for factors influencing the migration of HF fluid.Subsequently, due to incomplete data regarding the real-world case study, a sensitivity analysis was conducted through the simulation of 11 scenarios to evaluate impact of each factor.The tracking of HF fluid pathways was performed using MODPATH software.The results show that HF fluid can reach the aquifer in 99.05 years.Sensitivity analysis identifies key factors in HF fluid migration, including the hydraulic conductivity of the permeable pathway, the fractured shale, and the extent of the induced fracture.In contrast, the lack of a permeable pathway and the limited length of the induced fracture prevent any migration of HF fluid to the aquifer.