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What is Friction Angle?

For a planar, clean (no infilling) fracture, the cohesion is zero and the shear strength is defined solely by the friction angle. The friction angle of the rock material is related to the size and shape of the grains exposed on the fracture surface. Thus, a fine-grained rock and rock with a high mica content tend to have a low friction angle, whereas coarse-grained rock has a high friction angle.

Angle of Internal Friction

What is Unconfined Compressive Strength?

The unconfined compressive strength (UCS) of sedimentary rocks is a key parameter needed to address a range of geomechanical problems ranging from limiting wellbore instabilities during drilling, to assessing sanding potential and quantitatively constraining stress magnitudes using observations of wellbore failure.

Various applications can be used for the development of rock strength profiles along the wellbore. With testing on core samples, rock strength can be found using rock mechanical laboratory tests. Laboratory tests to find UCS can be done through uniaxial or Triaxial tests. Triaxial tests have to be carried out under different confining stresses to determine the failure criterion of a specific core depth.

What are In-situ Stresses?

In-situ stresses: Overburden and Minimum/Maximum Horizontal Stresses.

Underground rocks and sediments are subjected stresses, the principal ones being:

• Vertical stress
• Minimum horizontal stress
• Maximum horizontal stress

It is critical to identify the magnitude and direction of the horizontal stresses to understand stresses that are subjected to an element of rock in the formation. This information is vital in determining several parameters to have a successful drilling, fracturing, water injection and etc. operation.

The three principal compressive stresses.

Depending on the order of the principal stresses, different stresses regime can be identified which can be related to different fault regimes as defined by Andersonian tectonic regime

What is Tensile Strength?

Tensile strength is a measurement of the force required to pull something such as rope, wire, or a structural beam to the point where it breaks.

The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking.

What is Shear Modulus?

Shear Modulus is the ratio of Shear Stress to Shear Strain.

What is Geomechanics?

Geomechanics is the study of soil and rock structure and stability.