We develop physically representative models to predict the subsurface properties by interpreting signals. This is a broad and challenging task, and we adopt a fundamentally different approach for incorporating small-scale features (such as microfractures) by directly modeling the pore space and its alteration, rather than modeling the solid region based on common assumptions in poroelasticity or solid mechanics.
Our earlier study examined the interpretation of acoustic emission (AE) events to predict permeability enhancement at a block scale. Hydraulic fracturing enhances the transport properties of a tight formation, but it remains difficult to predict the enhancement as a function of AE events. The topology of the created fractures is a function of the heterogeneity of the pore space, the geometry of the preexisting fractures, and the pore structure of the intact void space. The induced fractures can have significant effects on transport properties, but it is unclear how these fractures, whose characteristic size is on the order of few nanometers to micrometers, are connected to each other and to the pore space at the 1-cm scale.
We used a physically representative pore model to implement the effects of the microfractures on the transport properties. The pore space was treated as a network of pore bodies (sites) that interact with each other through pore throats. Each event was representative of a microfracture or indicative of an asperity that compressed during fracture closure. Our assumption was that the small fractures form a connected-through path when the number of events per unit volume exceeded a certain value, which is relevant to the percolation threshold. 
Representative article
- Sakhaee-Pour, A., and Agrawal, A. (2018). Integrating acoustic emission into percolation theory to predict permeability enhancement. Journal of Petroleum Science and Engineering, 160, 152–159.