A ROBUST INTEGRATION BETWEEN GEOCHEMISTRY AND ADVANCED DIGITAL CORE ANALYSIS METHODS TO GENERATE HIGH-RESOLUTION POROSITYPERMEABILITY LOGS: A CASE STUDY ON A MAJOR UNCONVENTIONAL PLAY IN MIDDLE EAST

摘要

In Kuwait,the unconventional source and reservoir rock represented by Najmah Formation is characterized by a complex diagenetic history and depositional variability. This complexity makes the conventional evaluation methods alone insufficient to determine porosity and permeability logs accurately. A major goal of this study was to produce highresolution porosity-permeability logs for Najmah Formation using advanced digital analysis and geochemistry measurements. Sixty(60)feet of continuous core were analyzed from an oil field in South West Kuwait. The analysis started with dual-energy x-ray CT scanning of full-diameter whole core and core gamma logging. Plug litho-samples were selected to represent the varying porosity and organic matter content along the entire core length. Two-dimensional Scanning Electron Microscopy(2D SEM)and three-dimensional Focused Ion Beam(3D FIB-SEM)images were acquired and analyzed to accurately determine the kerogen content and porosity. Matrix permeability was directly computed from the 3D FIB-SEM images using the Lattice Boltzmann method. The SEM porosity was calibrated by determining the amount of movable hydrocarbons at in-situ reservoir conditions based on geochemical analyses(XRF,XRD and LECO),pyrolysis indices,Pressure-Volume-Temperature(PVT)data and desorption and adsorption isotherm experiments. The digitally obtained porosity and permeability data showed a unique trend that was used to produce permeability at the core level. The integration between digital analysis and geochemistry data increased the estimated porosity and confirmed higher mobile hydrocarbon in the reservoir in comparison with the measured data at the surface. This produced a new porosity-permeability trend that was more representative of the reservoir conditions and caused a significant increase in the rock permeability. The integration between the digital SEM analysis and the geochemical measurements was key in estimating in-situ porosity and permeability characteristics of the tight formation under study. Moreover,this analysis provided an important tool for obtaining different high-resolution porosity and permeability logs based on various porosity considerations(effective,organic,inorganic,clay). This would lead to increase certainty of reservoir properties by quantifying sensitivities of TOC,porosity,and permeability and their impact on volume of mobile hydrocarbons thus increasing the net pay in the main reservoir interval.