Construction of a True Triaxial Apparatus with the ability to simulate the hydraulic fracturing method through a direct injection system

A true triaxial apparatus was designed and constructed to simulate hydraulic fracturing test. The idea used in this machine facilitates the process of inserting the cubic specimen in its chamber and locating the injection system and vertical load on top of the specimen. It uses a specially designed injection unit. The injection unit incorporates a fluid punch system which provides fluid pressure up to ۲۰۰۰ bar and applies vertical pressure simultaneously in conjunction with the vertical jack. The injection fluid can be all type of fluids regardless of its viscosity and density. The injection unit is designed in an order that can rotate around one of the four vertical columns of the machine and using two articulated arms can precisely locate above the injection hole. The horizontal stresses in X and Y directions on rock specimens are applied using two pairs of hydraulic jacks which provide ۵۰ tons of force in each direction. The vertical jack provides ۸۰ tons of such force.Using a ۳۰×۳۰×۳۰ cm۳ calcareous rock two tests were conducted under vertical stress of ۸.۸۸ Mpa and without horizontal stresses and under horizontal stresses of ۲ Mpa in X direction and ۴ Mpa in Y direction. The borehole diameter was ۸ centimeters and the theory of hydraulic fracturing of breakage plane direction being perpendicular to the minimum horizontal stress was demonstrated.

Keywords:

Hydraulic fracturing , True Triaxial Apparatus ,