Hydrocarbon prospectivity of Al-Sirhan Basin, southeast Jordan

Abstract

Al-Sirhan area in southeast Jordan is studied for its hydrocarbon potentiality.Petrophysical studies including porosity,permeability,water saturation,and hydrocarbon saturation are done using wire line logs for candidate reservoirs.Total organic carbon analysis is done for two candidate source intervals.Seismic investigation is also done using seventeen seismic sections that cover almost the central and eastern part of the area.Finally,closures, reserves,and proposed migration pathways of hydrocarbons are studied in order to assess the hydrocarbon potentiality of the study area. Within the Cambrian sequence,Salib Formation is found to contain good porosity due to partial dissolution of feldspars,very low permeability,and high water saturation.This formation is capped by the shales of the overlying Burj Formation.Possible source rock is the carbonates of the Burj Formation.Several types of closures with good capacities exist within the Salib Formation.The major risks,when considering Salib Formation as a target for petroleum exploration,are low TOC content of the source rock,low permeability and high water content of the reservoir rock. Within the Ordovician and Silurian sequence,the glacially deposited Trebeel Formation is found to contain good porosity,low permeability,and low water saturation.This formation is caped by the shales of the overlying Batra Formation.Several intervals contain good source rocks within this system.These are the shales of Sahl as Suwwan Formation,the shale layers at the upper part of Umm Tarifa Formation,and the shales of the overlying Batra Formation.TOC analysis in the present study proved that Hiswa Formation might be considered good source rock.Organic carbon analysis carried by several petroleum companies indicated the high TOC content of the lower part of Batra Formation and the upper shale layers of Umm Tarifa Formation (Paleoservices,1989). Several types of closures are found within Trebeel Formation.All the main closures were tested by wells and found to be almost dry.Thus,the major risks when considering Trebeel Formation as a target for petroleum explorations,are the low permeability of the reservoir rock, and the lack of potential untested closures. The only way that might cause filling the closures of the study area with hydrocarbons is from the source rocks within the Al-Sirhan Graben in Saudi Arabia.As the graben formed deeper depositional environment during the Paleozoic Era,better source conditions exist within the graben.Thus,hydrocarbons might be generated in the graben and migrated through the Jordanian borders to reach Al-Sirhan closures which exist at higher elevations. This scenario forms high risk as the pathway is interrupted by several growth faults that provide possible paths for hydrocarbons to escape to the surface.Accordingly,the study area is classified as high risk area for petroleum exploration.