3D seismic interpretation of soft-sediment deformational processes offshore Israel : implications for hydrocarbon prospectivity

Abstract

This thesis uses a combination of industry seismic (2D and 3D) and well data to investigate the typologies, genetics and mechanisms of soft-sediment deformational processes on the continental margin of Israel and their impact on the exploration and production of hydrocarbons. Research has been focused on the two major types of soft-sediment deformation in the region: clastic diapirism and submarine slope instability (i.e. submarine slumping). Such processes have occurred almost continuously throughout the post-Messinian history of the Israeli margin, and have played a critical role in its overall evolution and construction. Detailed analysis of the timing of occurrence, areal distribution and 3D appearance of the resultant structures has enabled an enhanced understanding of the causes, processes and results of soft- sediment deformational events to be obtained. Clastic diapirism occurred during the first stages of refilling of the Mediterranean Sea after the Messinian Salinity Crisis, and was restricted to an area underlain by the Afiq Submarine Canyon (Oligocene in origin). The resultant bodies correspond to a series of four-way dip mounded features, and ridge-like structures that are mainly distributed along the axis and one of the flanks of the canyon, respectively. Seismicity and hydrocarbon generation have been proposed here as the main triggering mechanisms. Clastic diapirism plays a decisive role in the hydrocarbon prospectivity of the region as it largely modifies the reservoir properties and architectures of the largest accumulations of hydrocarbons discovered to date in Israel. Submarine slope instability (i.e. submarine slumping) is the second dominant typology of soft-sediment deformation in the continental margin of Israel. Submarine slumping initiated during the Late Pliocene with the Israel Slump Complex (ISC), one of the biggest submarine slump deposits in the world described to date. Since then, slope failure has occurred almost continually up to the present day. Submarine failure in the area is linked to the dynamics of subsidence and deformation of the transform margin of the eastern Mediterranean. Seismicity and presence of gas in the sediments, together with localised oversteepening, have been proposed as the main triggering mechanisms. The high spatial resolution provided by the 3D seismic data has enabled two principal types of submarine landslides to be distinguished according to their mechanism of frontal emplacement: frontally confined and emergent. In the first, the landslide undergoes a restricted downslope displacement and does not overrun the undeformed downslope strata. In the second significant downslope translation occurs since the landslide is able to abandon its original basal shear surface and translate freely over the seafloor. Such division is of critical importance as the formational mechanisms, and processes of translation and cessation are fundamentally different.EThOS - Electronic Theses Online ServiceGBUnited Kingdo