Brittleness Index and Toc As Potential Parameters in Brown Shale Formation Pematang Group on Outcrop in Limapuluh Koto Area, West Sumatra

Abstract

Brittleness index is an important parameter for success in hydraulic fracturing planning (Ju Hyeon Yu, et al, 2016). Jarvie et al (2007) and Wang and Gale (2009), stated that the brittleness index determines the magnitude of ductile and brittle values of the rock formations, based on their mineral content. Brittleness of shale hydrocarbon is required for initiation and propagation of fractures, and fracture re-opening. Rock formation with high brittleness value is easier to do hydraulic fracturing (Jingqi Xu, 2016).

Shale fracability can be determined based on mineralogical evaluation for optimal hydraulic fracturing planning. The XRD test of rock samples from the Brown Shale Formation, Pematang Group in the Central Sumatra Basin was conducted to obtain mineral content, which then can be used to determine the brittleness index.

A sample test of 8 rock samples was carried out from the outcrop of Brown Shale Formation, Pematang Group in Limapuluh Koto Area, as it was difficult to obtain core data from well drilling at the research site, as an approach considered representing target formation for the identification of shale hydrocarbon potential.

From laboratory test result of samples from Brown Shale Formation in Limapuluh Koto Area, it was quantitatively obtained that total organic carbon (TOC) value is 4 - 17 wt%; Brittleness Index: and 0.61-0.83 (average 0.73). From the results of Brittleness and TOC analysis, it can be concluded that Brown Shale Formation has a good unconventional shale hydrocarbon potential and can be used for further research, due to that oil production from conventional reservoir Indonesia in general has decreased significantly.