Porosity Modeling of Huge Thick Carbonates: A Case Study of Lower Paleozoic Carbonates in the Tazhong Uplift, Tarim Basin, China

Abstract

This study provides a solution to determine the porosity evolution of huge thick carbonates accurately using PetroMod version 2016.2 software with a cementation tool. The Lower Paleozoic carbonates from the Tazhong Uplift (Tarim Basin) were taken as examples. Results show that the errors of modeled porosity decreased from 256.3%–468.8% to 6.7%–12.5% for low-porosity carbonates and from 15.0%–22.9% to 2.9%–5.0% for high-porosity carbonates, indicating a better fit to the measured values after considering carbonate cementation. The calibrated model incorporating cementation exhibits typically low carbonate porosities and burial depths but high thermal conductivities, resulting in much lower formation temperatures, maturities, and hydrocarbon masses than the uncalibrated model. This study indicated that carbonate cementation plays a very important role in the reduction of carbonate porosity, and it is necessary to calibrate the thick-carbonate porosity model using the cementation tool. Although this method has certain feasibility and practicability and can be utilized widely to model huge thick carbonates, it has a limitation in recovering the increase in porosity caused by postdiagenesis.