Petrophysics of Source Rock Reservoirs: A Complete Workflow

Abstract

Abstract Source rock reservoirs have complex mineralogies and pore systems–their porosity varies from low to moderate, and their permeability varies from low to ultra-low and is in the nano-darcy range. The petrophysical evaluation of these complex reservoirs using only conventional logging tool (quad combo) data is highly complex and uncertain as a result of the tools’ limitation. Obtaining better and more certain petrophysical results for these reservoirs require integrating data from the conventional logging tool with the high-tech tools [elemental spectroscopy, nuclear magnetic resonance (NMR), dielectric, and spectral gamma ray]. It is challenging to calculate accurate porosity and water saturation values of source rock reservoirs using conventional log data. The presence of kerogen and complex mineralogies, such as conductive minerals, increases the difficulty. Because these petrophysical outputs are important for reserve estimates, any calculation error of these components directly affects the hydrocarbon in-place estimates. To address this issue, a new workflow has been developed to integrate data from conventional logging and high-tech tools. This paper demonstrates a workflow designed to characterize source rock reservoirs by integrating data from conventional logging and high-tech tools. Additionally, this workflow helps provide accurate petrophysical outputs that are used later to estimate the correct hydrocarbon in place. This workflow was tested in multiple source rock reservoirs in the Middle East region. This workflow also provides mechanical properties (including Poisson’s ratio, Young’s modulus, closure pressure, and brittleness) of source rock reservoirs. The integration of rock mechanics and petrophysical results helps identify sweet spots that can be selected for fracturing operations.