Organic geochemical and petrographical characteristics of the major lower cretaceous petroleum source rock (Makhul Formation) in Kuwait - Arabian Gulf

Abstract

The Lower Cretaceous Makhul Formation is one of the major petroleum source rocks in Kuwait. This study aims to evaluate the Makhul source rock for its organic matter richness and its relation to the rock composition and depositional environment. A total of 117 core samples were collected from five wells in Raudhatain, Ritqa, Mutriba, Burgan, and Minagish oil fields north and south Kuwait. The rock petrographical studies were carried out using a transmitted and polarized microscope, as well as SEM and XRD analyses on selected samples. Total organic matter TOC and elemental analyses were done for kerogen type optically. The GC and GC-MS were done as well as the carbon isotope ratio. The results of this study show that at its earliest time the Makhul Formation was deposited in an anoxic shallow marine shelf environment. During deposition of the middle part, the water oxicity level was fluctuating from oxic to anoxic condition due to changes in sea level. At the end of Makhul and the start of the upper Minagish Formation, the sea level raised forming an oxic open marine ramp depositional condition. Organic geochemical results show that the average TOC of the Makhul Formation is 2.39% wt. High TOC values of 6.7% wt. were usually associated with the laminated mudstone intervals of the formation. The kerogen is of type II and is dominated by marine amorphous sapropelic organic matter with a mixture of zoo- and phytoplankton and rare terrestrial particles. Solvent extract results indicate non-waxy oils of Mesozoic origin that are associated with marine carbonate rocks. The formation is mature and at its peak oil generation in its deepest part in north Kuwait.

Petrography and Geochemistry of Zubair Shale Formation in Rumaila Oilfield, Southern Iraq: Implications for Provenance and Tectonic Setting

“…Finally, the cycle was completed by the formation of a marine transgressive shale. However, when growth of a deltaic lobe has been renewed above a shale base, a new cycle starts [3]. The Zubair Formation is dominated by sequences of siliciclastic lithostratigraphic, with lim.…”

“…schemed in a shale field could reflect the clay minerals correlation, and source rocks can be felsic to intermediate in composition.Table(3) displays the trace element concentrations obtained from 12 oil shale specimens.Transitional trace element concentrations (for example, Mn, V, Ni, Cr, Zn, Cu, Zr, and Co) varied little in core shale. The existence of calcite and dolomite may explain the Sr concentration (25.25 to 300.66 ppm) in Zubair shale.…”

Reservoir evaluation of the Eastern Tethyan Middle Eocene Larger Benthic Foraminifera dominated carbonates from Pakistan.

“…Reef constructors have remained the primary constituent of the giant carbonate reservoirs. Tropical shallow marine carbonates of late Paleocene to early Oligocene are characterized by the dominance of Large Benthic Foraminifera (LBF) (Höntzsch et al, 2013;Bahman, 2022).…”