Yield Geomechanical Parameters of Talang Akar Formation Shale for Hydraulic Fracturing Feasibility in Shale gas field development
Dwi Tunggal Adiprayanto, Bagus Endar B. Nurhandoko2,3, Edy Sunardy1, Yoga A.1

1)Engineering Geology, Padjadjaran University
2)Mathematic and Natural Sciences Faculty, Institut Teknologi Bandung
3)Rock Fluid Imaging Lab

Abstract

Indonesia^s shale gas potential is very large since Indonesia has large reserves and wide distribution of oil and gas reservoirs. Shale gas development in Indonesia requires an in-depth and unique study that considers the oil play system in Indonesia is in an active tectonic area instead of a continental play system like in the USA and China.
Shale is a rock composed mostly of clay-sized mineral grains and is also called mudstone, a sedimentary rock that usually forms from the compaction of at least 50% silt and clay-sized particles. In nature, this shale combines clay minerals, i.e., illite, smectite, kaolinite, and non-clay minerals, i.e.: silica (Quartz), and carbonates, i.e., calcite and dolomite.
Shale gas is a reservoir, caprock, and source rock at once. Shale gas is targeted as a potential gas reservoir of natural gas. The quality of this shale reservoir depends on the thickness, extent of existence, organic content, thermal maturity, depth and pressure, fluid saturation, and permeability. However, this shale has very low permeability, and the economic production requires sophisticated stimulation techniques, namely hydraulic fracturing. This hydraulic fracturing technique requires an in-depth understanding of shale rocks^ subsurface stress tensor, elastic modulus, and failure criteria.
The yield strength value is the point of displacement or transition from the elastic zone to the plastic zone of shale rock. This yield strength value determines whether the rock^s fractures will remain open after being injected with proppant sand or closed again after the hydraulic fracturing. The fractures will close when the subsurface^s minimum horizontal stress (SHmin) is greater than the rock^s Yield Strength. The fractures are closed because the proppant sand sink into the shale rock since the shale rock enters the plastic zone.
This research shows that the yield strength of the Talangakar shale is higher than the SHmin value in the Beringin field, South Sumatra, Indonesia. Therefore, shale gas development in the Talangakar Formation can be feasibly produced with hydraulic fracturing to enhance reservoir permeability.

Keywords: Shale gas, Talang akar, South Sumatera, Geomechanics, Yield parameter

Topic: Earth and Planetary Sciences