Crustal architecture, heat transfer modes and geothermal energy potentials of the Algerian Triassic provinces

Abstract

The Triassic province is located within the Eastern Algerian Sahara, towards the Eastern edge of the M'zab Dorsal. Several hydrothermal reservoirs have been identified within this area along the Oued Righ valley and Rehabi-Berriane structural axis, forming an area of high temperature geothermal activity. The genetic mechanism of this geothermal system is currently unclear and needs urgent scientific reaction. In this work, we present a new conceptual model of the geothermal system in the Triassic provinces, using the structural model obtained through integrated study of recent edge detection techniques and the calculation of thermal proprieties of the middle and the lower crust. This multidisciplinary approach proposes a novel heat transfer mechanism and reservoir architecture within the province. We used spectral analysis on aeromagnetic data to determine the Curie point depth, geothermal gradient, heat flow, and radiogenic heat production. The results outlined the major structural trends within the Eastern Algerian Sahara. Deep heat flow sources were observed between 12.5 to 23 km depths and the geothermal gradient within the lower crust reaches 35 °C/km. The measurement of the thermal properties in petroleum wells indicates different thermal distributions. The delineated geothermal pattern is linked to the deformation of the Moho and the presence of deep-seated faults along the middle and lower crustal boundary. The shallow Curie point depth can be interpreted to be a result of the crustal thinning giving the high heat flow values. These results provide a physical representation of the heat transfer modes in the Oued Righ and constitute a unique continuous geothermal system within the eastern Algerian Sahara.