Organic-rich units

from the Pliocene and Eocene in the Levant and northern Israel

Source rock analysis of organic-rich units from the Levant and northern Israel

A land-based core beginning in the Early Eocene was drilled in Gilboa Mt., northern Israel. Of great interest are the lower 150 m of the core which is composed of organic-rich chalks interweaved with displaced neritic limestones. Total organic carbon (TOC) values range between 1.5 and 14%, averaging 3.5%. This core represents the first instance for which a thick organic-rich interval of 150 m was identified in Eocene deposits of Israel, raising a novel possibility for an undiscovered hydrocarbon source-rock. This study aims at producing a multiproxy assessment of this newly discovered source-rock by completing petrophysical, sedimentological and organic geochemical analyses. Displaced limestones (soft-sediment deformation, partially lithified rip-ups, folds, small diapirs, bed-scale imbrication) are composed of a variety of poorly cemented mud- and wackestones with low-diversity assemblages of larger foraminifera associated with planktonic foraminifera, suggesting deposition under oligophotic conditions on an outer ramp below the energetic zone. Consistently higher TOC values are measured within the limy allochthonous facies. Principal components analysis (PCA) was used for comparing elemental XRF data with TOC, petrophysical measurements, and sedimentological features. High Zn, P, S and Cr values clustered with organic-rich samples, most likely related to the affinity of micronutrients with marine organic carbon, and to natural sulfurization processes connected with its preservation. Ca clustered broadly with organic-poor samples. Elements of terrestrial affiliation (i.e., Al, Si, Fe and K), high abundances of benthic fauna, and high magnetic susceptibility values clustered with the highest TOC samples, suggesting a link between sedimentary transport and accumulation and/or preservation of organic matter. The early Eocene in our region is thus regarded as a source rock in two separate categories: 1) as a self-sourcing reservoir, similar to the Upper Cretaceous oil shale deposits, and as it is being currently prospected by Shell in Jordan, or 2) as a potential source rock for offshore hydrocarbon generation. The identification and characterization of potential source rocks in a prospected area is one of the main building blocks of an applicable petroleum system model, and one of the directives of the Ministry under the category of ‘fissile fuels.’

Project funded by the Ministry of National Infrastructures, Energy and Water Resources.