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Gravitational/Vertical Stress - Coggle Diagram
Gravitational/Vertical Stress
Definition
Vertical stress also known as overburden stress
The sum of all the pressures applied by all of the different rock layers
Every formation contains fluid and rock and each one must be encounted for separately
Porosity correlation can be simply used to define the amount of space that is occupied by fluid versus the amount of space that is occupied by rock
Methods of stress determination
The hydraulic fracturing test
Why?
-The hydraulic fracturing tests were conducted to determine the in-situ state of stress to design the underground powerhouse in the present investigation.
Hydraulic fracturing involves applying hydraulic pressure to a drill hole to determine the fracture pressure and hence the stress.
How?
The vertical stress was calculated based on the height of the overburden at that location. A length of borehole is chosen for the stress measurements and an interval, typically 1 m long, is located for the test and isolated using a straddle packer system.
Several Problems
It is often a completely unjustified assumption that the borehole is indeed parallel to a principal stress. The hydraulic fracturing method is the only direct method available for stress measurement at any significant distance from the observer
Example of gravitational/vertical stress
Calculation
Simple calculation to determine vertical stress
