OpeningFracture Robustness Analysis of Talang Akar of the South Sumatra Shale Due to Hydraulic Fracturing based on Geomechanical Parameters Dwi Tunggal AP, Edy SUnardi, Bagus Endar
Padjadjaran Univ, Padjadjaran Univ, ITB
Abstract
Abstract. Hydraulic fracturing, commonly known as fracking, is a technique widely used in the extraction of gas from shale gas reservoirs, especially those characterized by low permeability. The main goal of this process is to produce artificial fractures that increase the free flow of gas to the surface. These fractures are kept open with a supporting material called proppant. The success of hydraulic fracturing relies heavily on a comprehensive understanding of geomechanical parameters. These parameters cover a wide range of geomechanical properties, including but not limited to permeability, Young^s modulus, Poisson^s ratio, friction angle, formation pressure, and existing geological and tectonic conditions. Analyzing these parameters is critical to understanding rock behavior under pressure, applied forces, and proppant resistance in sustaining artificial fractures.
Hydraulic fracturing design is a complex process that takes into account factors such as injection pressure, proppant selection, and fracture geometry. Geomechanical studies play an important role in predicting long-term fracture behavior, and the use of 3D modeling of pore and fracture pressures is critical in the design and optimization of hydraulic fracturing processes, ultimately increasing the productivity of oil and gas wells. Anisotropy in shale formations indicates the heterogeneity of the physical and mechanical properties of shale rocks in various directions. These characteristics are particularly important in the context of shale gas production, because anisotropy influences the mechanical strength, permeability, fracture orientation, and shrinkage behavior of shale rocks during gas extraction. Alignment of shale layers plays an important role in well stability and gas production efficiency. Pores parallel to the layers exhibit varying degrees of permeability, and fractures parallel to these layers may serve as preferential channels for gas flow. In addition, the shrinkage behavior of shales can vary depending on the direction of the layers. The Talang Akar Formation, located in the South Sumatra Basin, has quite large shale gas potential. This formation was deposited in a slack phase with low depositional energy during the transgression period, resulting in abundant shale deposits. It is known for its shallow marine depositional environment with Type II/III kerogen and lakes with Type III kerogen. Geologically, the Talang Akar Shale is believed to be the dominant source rock of commercial hydrocarbons in the basin, thus demonstrating its potential as a shale for oil and gas extraction. Advanced seismic data processing techniques, such as seismic attribute and spectral decomposition, indicate that certain areas within the formation are estimated to have a Total Organic Carbon (TOC) content greater than 2%, qualifying the area as hydrocarbon shale.
The study of unconventional oil and gas resources in the Talang Akar and Lahat/Lemat Formations is estimated to be quite large with potential reserves reaching 4200 MMBOE (Million Barrels of Oil Equivalent). This highlights the formation^s promise as a significant contributor to the future of energy resources. For further study and exploration, geophysical methods such as seismic inversion and seismic attribute analysis can be applied to predict TOC distribution and fragility index, especially in the center of the basin where the shale quality is interpreted to be better than the flanks. The relatively young age of the shale compared to North American shale suggests that the Talang Akar shale may be less brittle, with brittleness index values likely ranging between 40% - 70%. One of the main problems for the success of hydraulic fracturing is estimating the stress parameters of the subsurface stress and the strength of the fracture plane to support the proppant granules. Therefore, they remain open after the hydraulic fractional fracturing process. These proppant granules should maintain the fracture opening after the hydraulic fracturing process for as long as possible. The robustness of maintaining rock fracture openings after hydraulic fracturing depends on the strength of the rock and subsurface stress. In this paper, we present various parameters that influence the robustness of fracture planes in the Talang Akar Shale formation, namely the subsurface pressure pattern of the Talang Akar formation, South Sumatra. Geomechanical parameters that directly influence the robustness of fracture planes to subsurface pressure, namely yield parameters at varying depths. , mineral content of Talang Akar Shale, and elastic parameters that have the most potential to be predicted.
