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CLASSIFICATIONS AND METHODOLOGIES OF RESERVES CALCULATION IN UNCONVENTIONAL TIGHT/SHALE GAS RESERVOIRS
Abstract
The article presents methods for determination of technically recoverable resources from unconventional reservoirs in shale rocks. The gas flow in low-permeable unconventional deposits is a complex process, depending on rock parameters but also on the method of well stimulation. Significantly higher complexity of parameters affecting the operation process requires the construction of complex numerical reservoir models taking into account various gas flow mechanisms: flow according to the Darcy equation in fractures and mesopores, nano permeability, influence of molecular and Knudsen diffusion, the effect of the desorption process, the impact of microporosity on the properties of PVT, natural density of fractures, geomechanical properties or configuration of the geometry of artificial fractures generated during well stimulation. These models are much more complicated than conventional bed models, and although in most cases they are limited to the single well drainage zone, the time required for simulation is considerable, and thus the number of projects is limited. One of the possible solutions is to use the concept of replacement models based on artificial intelligence tools, such as artificial neural networks. The principles of resource estimation applied by SPE (PRMS) as well as the principles of resource estimation by the Polish classification are presented. Four main methods of resource estimation are presented: volumetric, geochemical, operational (DCA) and a new approach using classical mathematical modeling of the gas flow in the deposit, probabilistic methods and elements of artificial intelligence. The impact of technology on changes in technically recoverable resources was also discussed.
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References15
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