Shale gas reservoirs are mainly characterized by their low permeability and by having geomechanical, petrophysical and geological characteristics different from conventional reservoirs. Successful production of this type of reservoir depends on two aspects, its hydrocarbon generation potential and the ease of extraction. Therefore, characterizing and determining the natural fracture zones that will be connected by the drill bit and hydraulic fracturing is essential before orienting and defining the well trajectory. This article will characterize reservoir properties in terms of its geomechanics and petrophysics, specifically rock brittleness, since they are the main determining factor for selection of shale gas reservoirs with potential to be exploited. Brittleness is determined from geomechanical properties, consequently, indicating higher brittleness values to rocks with high Young's modulus and low Poisson's ratio, which translates into rocks rich in quartz, and lower values to rocks with low Young's modulus and high Poisson's ratio due to its organic richness and high content of clay minerals. This brittleness index involves the following properties: elastic and resistance parameters, pore pressure, total organic matter content and porosity, which show changes according to the different compaction trends that the rock has undergone. Finally, the evolution of pore pressure and compaction trends as a function of time will be analyzed to determine rock brittleness at each stage of burial. Concluding that rocks prone to fracture present overpressure, a high Young's modulus, and a low Poisson's ratio, have low porosity values and TOC between 1% and 3%.


In recent years, shale gas reservoirs have been considered as a potentially economic resource, thanks to the high energy demand evidenced in countries such as the United States of America where natural gas consumption was 31.01 trillion cubic feet (EIA, 2019), and the technological development that has allowed its exploitation. However; the study and characterization of this type of reservoir turns out to be complicated, because they are reservoirs that have a matrix with ultra-low permeability and are notably different from conventional reservoirs, in terms of their geology, geomechanics and petrophysics (Dewhurst et al., 2015). In addition to their total organic matter content that makes them an interesting area. Therefore, to generate production from this type of reservoir, not only artificial fractures are required but also natural fractures, which constitute important flow channels (Nordeng, 2009), however, the little study of this type of fractures in reservoirs unconventional means that the success of its commercial production is not guaranteed.

Therefore, the need arises to characterize properties of shale gas in terms of geomechanical and petrophysical attributes that intervene in formation of fractures. The methodology developed will allow oil companies to correctly select the candidate strata to fracture and, therefore, to create flow channels to wells.

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