High-Resolution Distribution of Organic Matter in Carbonate-rich Oil Shales controlled by climatic cycles and depositional environments

Abstract

The objective of this joint sedimentological and organic matter study was to document and understand the vertical heterogeneity of organic matter distribution of an oil shale interval which belongs to the lower Muwaqqar Fm in Jordan. The high resolution logging of organic carbon using new pyrolysis instrument reveals the cm-scale rhythmic bedding of the oil shale deposits. Cyclostratigraphy based on recognition of Milankovitch cycles appears to control the alternation of rich and lean organic layers within this carbonate interval. Introduction The objective of this joint sedimentological and organic matter study was to document and understand the vertical heterogeneity of organic matter distribution of an oil shale interval which belongs to the lower Muwaqqar Fm in Jordan (fig. 1 and 2). Because organic carbon content may show significant variation (e.g. at the mm or cm scale), a new instrument was used for recording high resolution logging of organic carbon on cores: the LIPS (Laser Induced Pyrolysis System). Study program Detailed investigation of one cored well (around 130 m long) has included high-resolution sedimentological logging (1:50 scale) and organic matter measurements (1 data point / 2 cm using LIPS on cores. Low resolution Rock-Eval data were acquired in order to calibrate the LIPS signal for calculating high resolution TOC and petroleum potential, regarding the different sedimentological facies. LIPS: a new instrument for high resolution logging of organic carbon Methods usually applied to quantity the carbon content or the hydrocarbon potential of sediment samples (Rock-Eval, Fisher Assay, Leco, analysis of thin sections, Iatroscan…) are expensive, provide low resolution data (typically, one sample every 30 cm to 2 m) and are time and sample consuming. Processing of geophysical well logs provides low-resolution logs (about 30 - 50 cm of mobile average data).