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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Prediction of Apparent Cohesion, Angle of Internal Friction and Poisson’s Ratio of Various Types of Rocks Using Laboratory Measured Unconfined (Uniaxial) Compressive Strength

Musaed Al-Awad1; Bandar Al-Anazi2

(1) Petroleum and Natural Gas Eng. Dept, King Saud University, Riaydh, Saudi Arabia.

(2) Petroleum and Gas Center, King Abdulaziz City for Science & Technology, KACST, Riaydh, Saudi Arabia.

The evaluation of Mohr-Coulomb failure criterion as well as other mechanical properties for reservoir rocks is essential for well planning, development and characterization of oil and gas reservoirs. This is because the understanding of the rock-stress relationship can solve many reservoir problems and avoid cost of remedial work. For example, a Mohr-Coulomb failure criterion may be used for borehole instability analysis, water injection design, hydraulic fracturing design, production optimization techniques, compaction and sand production prediction, etc.

A Mohr-Coulomb failure criterion is a function of the apparent cohesion and the angle of internal friction The evaluation of these two parameters requires testing of many rock samples using an expensive and time-consuming triaxial testing set-up.

In this study, a correlation between the apparent cohesion and the unconfined (uniaxial) compressive strength was developed. It is based on laboratory data of more than 282 rock samples of different types obtained from the literature.

The correlation coefficient of the developed correlation equals to 0.88. Verification of the developed correlation using data from other references has shown an average error of estimation less than 10%. Unfortunately, some odd predictions were also notices and can be attributed to measurement errors.

Therefore, the Mohr-Coulomb failure criterion’s parameters as well as Poisson’s ratio can be estimated using the developed correlation based on fast and cheap measurements of the unconfined (uniaxial) compressive strength.