THE recently developed True TriAxial Stress Cell (TTSC) has been modified to anaylse a wider variety of underground conditions which could help improve the safety of drilling for oil and gas deposits.

Curtin University PhD candidate Mohammed Asadi created the Fracture Shear Cell (FSC) as part of his PhD research project into the existing infrastructure of the TTSC, which simulates the conditions and changes encountered when drilling for oil and gas deposits located kilometres into the Earth.

The FSC is a modified version of the TTSC and allows for fracture shearing tests which provide information about the potential production capacity in fractured reservoirs.

By simulating the shear displacement of the two sides of a large scale fault or fracture in the presence of existing forces in the earth, the FSC also helps to build an understanding of what different events, such as an earthquake, do to a fractured reservoir.

Mr Asadi says there were a number of steps to the modification process.

“To place the sample into the cell new frames and shims were designed. These help in applying horizontal and vertical forces to the fracture surface.

“Also, to keep the normal force constant during the experiment a duplex pressure chamber was used.

“This has two sides one filled with Nitrogen gas and the other one with fluid. The gas acts as a compensator which keeps the pressure unchanged.”

The large loading capacity of the TTSC (up to 15000 psi) together with the use of accurate hydraulic pumps with the ability to apply constant rate shear load are some of the unique capabilities of the FSC.

Curtin’s Department of Petroleum Engineering Senior Lecturer Dr Vamegh Rasouli says the new test analyses earth conditions that are usually looked over.

“Considering the effect of surface morphology is critically important when hydro-mechanical behaviour of fractures is studied. This is usually ignored in practical applications to simplify the problem.”

Dr Rasouli says there are potential applications for the FSC in several industry areas.

“The results of experiments on synthetic and real fractures demonstrate the applicability of the equipment to be utilised for industry application.

“Studying the fracture or fault reactivation during reservoir depletion or injection, slope stability analysis of fractured rock masses and identifying potential block slippage or falling in underground spaces are potential industry applications for the FSC in the fields of petroleum, civil and mining engineering. “