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Integrated Kerogen Characterization in Terms of Source Rock Evaluation and SCAL - Case Study From North Kuwait

Abstract

Organic-rich Najmah Kerogen, of Lower Kimmeridgian to Upper Oxfordian age, comprises of thinly laminated Kerogen with calcareous mudstone deposited in deep basinal environment. It has a consistent thickness of 50′ in the entire study area with an average porosity of 4-6pu with a nanodarcy permeability and is the main source for hydrocarbon plays in Kuwait. This rock sequence occurs at depths of 13000-14000ft under HPHT conditions. Huge success of shale gas play in North America has prompted the characterization of these source rocks to evaluate their resource play potential for the first time in Kuwait. As per the Rock Eval and TOC analysis on the all seven layers identified within Kerogen revealed that the TOC varies between 3 to 22%. Vitrinite reflectance varies from 1.07 to 1.19 in general. The SEM and thin section of all the seven layers indicate that the Najmah Kerogen is essentially an organic carbonate and calcite is the dominant mineral (70%), quartz 5%, kerogen around 10-22% and clay is in the range of 7-19% in all the layers except the lower most layer where it is around 29% in few wells Cocoliths are fairly common. The mid Kerogen is relatively higher in calcite percentage around 70-80%. As envisaged earlier the mid layer is the low gamma is being considered for placement of horizontal well and may act as “carrier bed”. The hardness percentage of Kerogen from the Ternary diagram of TOC, Soft and hard apexes clearly demonstrate that Najmah Kerogen samples fall towards “brittle” apex signifying that the potential to frack the kerogen. As per the source rock evaluation of the Najmah Kerogen is inferred to be Kerogen Type-III and Gas prone. Petrography of Kerogen SEM and thin section descriptions reveal that the Kerogen Pelicypod Lime packstone to pelloidal Lime wackstone. The flank area in between the two structures is the area delineated for the placement of the horizontal location of Najmah Kerogen. The area has high potential in terms of hydrocarbon prospectivity based on S2 derived oil from Kerogen, gas from Kerogen and oil in rock and their maps along with the TOC maps reveal the best locations in the flank area. The current study has brought out the potential of Kerogen and needs to be probed by first horizontal appraisal location and the success would trigger the intense activity.