Rock Dilation or Shearing and associated Technologies

There is more than one definition of rock Dilation:

1.   Rock Dilation is a permanent deformation registered in rocks that are subjected to non-uniform dynamic stress. It can be best explained as volume changes, porosity increases from original by several folds and permeability increases in some cases more than 700%, due to micro-fracturing.

Rock Dilation

2.   Dilatancy is the increase in volume of a granular substance when its shape has been altered due to increasing the distance between its component particles.

Rock Dilation or Shearing Concept from University of Texas at Arlington:
http://geotech.uta.edu/lab/Main/DIRECT%20SHEAR%20TEST.pdf

3.   Rock Dilation is the deformation by expansion or volumetric change of the rock properties.
Technologies that will use effect of shearing to fracture potentially productive zone during Completion or for well stimulation can be considered cost-effective methods for hydrocarbon production. At Sigor Corporation we designs each SWTorpedo Tool specific to each producing or potentially productive interval.

Figure 1. 
A and B - Tool Head; C -Top view Tool Head attached; D - Complete Tool assembly; E - Schematic view of internal design.

SWTorpedo internal designs are individual for each well and  No mass production is possible.

High explosives such as PENT, HMX or RDX are strategically placed in the Tool and detonated in rapid succession to generate multiple shock waves that in return create a changing in time stress state when it is higher than Yield strength, at that point shearing progresses, and fast growing increase in rock volume can be observed, even though active forces are still working in compressive regime.

An explosive force creates pressures in the magnitude of 6 x 10⁵ – 1.2 x 10⁶  Psi. In such an environment, areas of initiated fractures and rock crushing are multiple. The area of dilated rock or micro-fractures is on average 6 times larger than an area of radial fractures.

Shear strength of rock's sediment depend on:

1.   Normal stresses

2.   Cohesion

·       Electrostatic forces important for particles < 1 micron

·       Chemical bonds are not important

3.   Internal friction

·       Resistance of particles

·       Angle of internal friction depend on:

1.    Grain arrangement

2.    Grain size

3.    Shape of grain

4.    Resistance to crushing (strength)

Factors that affect deformation are:

1.   Dilatancy

2.   Grain crushing

3.   Size of the grain

4.   Thermal characteristics

5.   Spatial variations in bed strength

6.   Decoupling

Figure 2.  Volumetric deconsolidation of sandstone:
    Line 1 (dash) depict static loads as a precondition,
    Line 2, 3 and 4 depict dynamic stress generate by multiple shock waves.
    Where:

q                      Volumetric deformation by expansion or Dilatancy
σ₃/σ₁=-1            depict by Line 1 and 2
σ₃/σ₁=-0.144     depict by Line 3
σ₃/σ₁=-0.132     depict by Line 4
σ₃/σ₁=0.7          depict by Line 5