Petrophysics Evaluation for Determining Porosity of Shale Reservoirs

Abstract

Indonesia is known for its large potential of shale resources, yet the character of their physical properties remains unclear. This study focuses on how to assess the petrophysical properties of shale using conventional wireline logs. Shale has been largely known as a host rock producing hydrocarbon in the conventional petroleum system due to the amount of kerogen trapped during the depositional process. The kerogen or continuously called Total Organic Carbon (TOC) behaves like a porosity to a density log and this will be misleading to the higher porosity than the actual shale rock. Prior investigation evaluates the physical properties in shale rock, including shale porosity, TOC, and matrix mineralogy, at a certain limited depth. A solid rock is presumed to consist of a shale matrix and TOC. Meanwhile, shale porosity is contained only in water. TOC responses to sonic wave, density, and porosity logs. We calculated the experimental data to estimate the volume of TOC at the limited depth to obtain the correlation of available logs. Shale porosity is then computed using a density log with the TOC-influence removed. The results show that the shale porosity is to be TOC-free with a value range of 3-14%.