Geochemistry and Reservoir Properties of the Upper Jurassic Formations, in Selected Oilfield Central Iraq

Abstract

Abstract Geochemical analysis of subsurface organic matter in the most productive source rocks, the Sargelu and Naokelekan formations, has provided insight into the potential of hydrocarbon production in the Jurassic strata of the selected oil field in central Iraq. The aim of this study is to conclude if the source rock can provide reservoir properties such as porosity and permeability. This attempt is made to support petroleum production from both reservoir and source rocks. The cause of this idea was adopted due to some of very good source rock were kept the produced hydrocarbons within the thin impermeable layers. Rock Eval pyrolysis returned high total organic carbon ranging from 0.55 to 34.82 wt%, Type II kerogen with a hydrogen index of up to 368 mg HC/gTOC, and a rock potential of 0.58 to 50.9 kghc/ton rock. Mature organic material was found in both formations, with a Tmax between 434 and 450 °C. This study of source rock properties shows that the rocks have good properties that need to be considered as the Sargelu and Naokelekan formations are the main sources of hydrocarbons in the studied area. The multi-story source-reservoir rocks are represented in this secession. The reservoir properties of the Naokelekan Formation are impressive in that it can draw crude oil from the underlying Sargelu Formation, which produces oil and releases it into the local petroleum system. The effective porosity in the Naokelekan Formation reached 14% in the main reservoir area, while permeability values mostly reached 4 mD. This indication potentially underscores the objective of this study to upgrade the oil-producing source rock into reservoir intervals.