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Multi-scale study of the organic matter in Najmah formation and its implications for fractures and petrophysical properties in the Sabriyah field, North Kuwait, A
Al-Qaod, Moath
Al-Qaod, Moath
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2023
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Abstract
The Sabriyah field is one of the largest producing fields in Kuwait that is mostly domi- nated with carbonate-rich lithology in Jurassic interval. The Najmah Formation was consid- ered the hydrocarbon source for most Sabriyah field reservoirs until unconventional reservoirs were explored in Kuwait. Production from Najmah Kerogen member has not begun yet. However, the Najmah Kerogen has a high potential from the excellent source beds that con- tain total organic carbon content (TOC) ranging from 2.13-12.26 wt.% with an average of 8.3 wt.% and vitrinite reflectance (Ro) of 1.28-6.6%. However, the organic matter related to the pore structure, petrophysical properties, fractures and geomechanical properties, reservoir quality, and regional analogs is still not clearly understood.
The methods used in this study integrate core petrographic thin section analysis, Field Emission Scanning Electron Microscope (FESEM), Focused Ion Beam Scanning Electron Microscope (FIB-SEM), X-Ray di↵raction (XRD), source rock geochemistry and pyrolysis for TOC, logR Passey method for TOC estimation, core porosity and permeability analy- sis, dynamic geomechanical elastic rock properties’ analysis, stereonet fracture, static earth modeling, and basin tectonic modeling. These analyses are then compared to the Niobrara and Haynesville formations.
The findings of this research are summarized as follows: (1) the mature organic matter improves the reservoir properties through the increase of the porosity and pore connectivity that increase the permeability, and reservoir quality of the Najmah, Niobrara, and Hay- nesville formations. However, it can cause an overestimation in the organic-rich zones of the well logs and thus needs kerogen correction. (2) The organic matter is the main contribu- tor to porosity and pore connectivity, confirmed by the FIB-SEM 3D modeling of the S-11 sample of the Najmah Kerogen. (3) The dominant porosity of the Najmah Kerogen is the organic matter porosity, which di↵ers from the Niobrara and Haynesville that are dominant
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in the matrix. (4) The elastic rock properties classified the Najmah as a ductile formation. (5) The fractures for the Najmah Kerogen in the Sabriyah Field are similar to the Niobrara and Haynesville trending of NW-SE, N-S, and NE-SW directions for Najmah, NE-SW, and NW-SE directions for Niobrara, and NW-SE direction for Haynesville formations that can be used in the process of well placement, drilling, and reservoir hydraulic fracture stimulation of the future reservoir and field developments.
This research study focuses on providing descriptive information on the petrophysical and fracture modeling of Najmah Kerogen reservoir variations as a function of organic mat- ter content and mineral composition. In addition, this research extends our understanding of the unconventional reservoir potential of the Najmah Kerogen by performing a high- resolution study of the pore structure/ architecture to characterize the pore composition, pore connectivity, mineralogy, and organic matter content, and its relation to the rock prop- erties, petrophysical properties and fractures of Najmah Kerogen. Thus, this research helps delineate the di↵erent properties of the overmature Najmah Kerogen and its permeability association. It will provide a detailed geological and petrophysical guide for future studies and reservoir field developments of well-design production plans from the Najmah Formation as an unconventional reservoir.
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