A large carbonate oil field in Iran is suffering from severe casing collapses and related operational problems in salt layers of Gachsaran cap rock Formation. To investigate the causes and cures of operational problems, specifically casing collapse, knowing mechanical characteristics of salt layer of this Formation is a prerequisite. However, taking core in this Formation is very difficult bellow the depth of 300m due to high solubility and weakness of the rocks, therefore surface samples should be obtained to study the mechanical behaviour of this rock. This has risen the doubts on the validity of these studies when they are extended to higher depths where the tempreture is quite different from surface.
In this paper, a series of mechanical tests are performed on shallow depth salt rocks at different temperatures (23°C–100°C). It is found that the mechanical parameters have different reactions to changing temperature. It shows that compression and shear wave velocities, dynamic elastic, shear and bulk modulus decreases by increasing temperature. However, dynamic poisson ratio shows increase. Both uniaxial compressive strength and axial strain increase with temperature, whereas the tangent modulus Et goes to an opposite direction. Meanwhile, the plastic strain increases gradually and strain-softening behavior of the samples becomes increasingly evident. The relations between dynamic and static modulus at various temperatures are also investigated.
