Pressure modeling fracture

Mercury porosimetry (or intrusion) Measurement of the specific porous volume and of the pore size distribution function by applying a continuous increasing pressure oti liquid mercury such that an immersed or submerged porous solid is penetrated by mercury. If the porous body can withstand the pressure without fracture the Washburn equation, relating capillary pressure to capiUaiy diameter allows converting the pressure penetration curves into a size distribution curve. If a sample is contracted without mercury intrusion, a specific mechanical model based on the buckling theory must be used... 

In the case of the high confining stress of deep reservoirs and the low fluid viscosity the fluid pressure along fracture faces is nearly constant. Therefore two models of fracture loading are considered. 

In Chapters 2 and 3, we introduced distributions of sources and vortexes to model fractures and shales. There, we obtained explicit solutions for the pressure field and its Darcy velocities. Here we will determine in a general manner the streamfunctions associated with those pressure solutions. We will develop, for simplicity, the formulas for constant density liquids. 

Lee, W.S. "Pressure Decline Analysis with the Christianovich and Zheltov and Penny Shaped Geometry Model of Fracturing," SPE/DOE paper 13872, 1985 SPE Low Permeability Gas Reservoirs, Denver, May 19 22. 

Lee, W.S. "Fracture Propagation Theory and Pressure Decline Analysis with Langrangian Formulation for Penny-Shaped and Perkins-Kern Geometry Models," SPE paper 17151, SPE Formation Damage Control Symposium, Bakersfield, February 8-9. 

It is obvious that in the case of pressure gradients determined by the maximum controlled by buffer reactions in the pile of rocks, and by the minimum in fractures (in the case of open circulation Pf(n,in) - (hydr) of the column of fluid), mechanical movement of the fluid was in one direction — from rock to fracture. For movement in the opposite direction—from fracture to rock—it was necessary to create a corresponding pressure gradient. Such phenomena, in addition to diffusion along the concentration gradient, presumably have occurred in hydrothermal metamorphism with typical reactions of hydration and carbonation. However, for normal progressive metamorphism it is hard to imagine a mechanical model in which a fluid with a strictly constant value of / h,o " h,o introduced from... 

The selection and preparation of sites for any of these gas stores is a fairly delicate process, because tightness can rarely be guaranteed on the basis of geological test drillings and modelling. The detailed properties of the cavity will not become fully disclosed until the installation is complete. The ability of the salt cavern to keep an elevated pressure may turn out not to live up to expectations. The stability of a natural rock cave, or of a fractured zone created by explosion or hydraulic methods, is also imcertain until actual full-scale pressure tests have been conducted. For the aquifers, the decisive measurements of permeability can only be made at a finite number of places, so surprises are possible due to rapid permeability change over small distances of displacement (Sorensen, 2004a). 

---