Organic shale analysis using geochemical data and seismic attributes: Case study of Talang Akar formation, South Sumatera Basin

Abstract

A case study of hydrocarbon prospect evaluation in north Exito field by using seismic attribute and seismic inversion AIP Conference Proceedings 1862, 030193 (2017) Corresponding author: aharis@sci.ui.ac.idAbstract. Organic shale analysis of Talang Akar Formation, south Sumatera basin has been carried out using integrated seismic attributes, petrophysical and geochemical data. This shale layer has been deposited in sagging phase with low deposition energy at transgression period, which results in abundant shale deposit. The paper is aimed at characterizing the geochemical and petrophysical properties of shale rock formation and mapping their distribution using transformed seismic data into acoustic impedance and Total Organic Carbon (TOC). The assessment of this shale formation is carried out by first analyzing rock physics properties to identify the interest zone of a reservoir. The next step is performing geochemical analysis to quantify TOC and determine the maturity level of the shale formation. In order to map the shale formation distribution, we transform seismic data into acoustic impedance and further into organic-rich shale (TOC) distribution. Our analysis of petrophysical and geochemical properties shows that there are two interest zones, in the depth interval of 2030-2182 m (zone A) and 2204-2396 m (zone B). Both zones are predicted as shale layer that has very good organic richness criteria and fulfills sufficient maturity level. In addition, the shale layer distribution is represented by inverted acoustic impedance and TOC, where we found the consistent information related to identified interest zone A and B, which is indicated by relatively low impedance and relatively high TOC. Further, these two zones (zone A and B) are predicted as the potential sweet spot to be explored as unconventional hydrocarbon resource.

Unconventional Resources of Shale Hydrocarbon in Sumatra Basin, Indonesia

“…The relationship between TOC and available log data for Talang Akar formation of South Sumatra basin is presented in Eq. 7 [14]. TOC = − 1.74 + 0.00038 × GR + 1.023 × Density − 0.0058 2 * Neutron + 0.00 62 * Sonic (7)…”

“…Figure 9 shows the sweet spot distribution of shale hydrocarbon of Talang Akar formation of South Sumatra basin. Figure 9a and b illustrate the AI and TOC map for upper Talang Akar formation, respectively, while Figure 9c and d present the AI and TOC map for lower Talang Akar formation, respectively [14]. The sweet spot of shale hydrocarbon is illustrated by red dashed line, which is indicated by low acoustic impedance (less than 27,500 ft/s*gr/cc) and relatively high TOC (greater than 2%).…”

“…Geochemical assessment of shale hydrocarbon of Talang Akar formation in South Sumatra basin, which was derived from SSB well[14].…”