Integrated Diagenetic Evaluation to the Characteristic of Shaly-Sand Reservoir in Gumai Formation, South Sumatera Basin, Indonesia Mira Meirawaty (a*), Firman Herdiansyah (a), Cahyaningratri P.R.(a)
a) Geological Engineering Department, Universitas Trisakti, Jakarta City, Indonesia
Abstract
One of Indonesia^s most productive oil and gas basins is the South Sumatera Basin, with discoveries in more than 300 oil and gas fields. The basin itself is a back-arc basin consisting of several sub-basins: the Jambi, Central Palembang, North Palembang, and South Sumatera sub-basins. The reservoirs are currently dominated by coarse to medium siliciclastic play. One interesting thing is that the muddy and fine siliciclastic succession also has the possibility of a low-resistivity reservoir by inter-formation or even intra-formation migration. Hence, this study will report the characteristics of the fine-to-very fine siliciclastic reservoir of Formation Gumai based on its lithology, facies, and diagenetic process. The study was conducted by megascopic observation goes along with microscopic analysis of subsurface core samples from the Gumai Formation interval in well ^X^. A total of 20 core samples from 5457 ft-5789 ft depth has been analyzed. Two lithologies are recorded in the reservoir zone: the coarser-grained sandstone with abundant shale dispersed in the upper section and the interlaminated fine-grained sandstone shale in the lower part. Due to petrography analysis, some diagenetic processes were recorded on the Gumai intervals, such as cementation, recrystallization, replacement, compaction, and dissolution. The integrated macroscopic-microscopic analysis will build a frame of shaly sand characteristics in the research area, with facies and diagenetic approaches that are linked to potential reservoir porosity.
Keywords: Diagenetic, Gumai Formation, Shaly-Sand Reservoir, South Sumatera Basin
