Assessment of the Effects of Temperature, Confining Pressure, and Loading Rate on the Geomechanical Behavior of Caprock of Asmari Reservoir in Iranian Oil Fields

Casing collapse is one of the costly and safety-threatening incidents in the oil industry. For example in Kupal oil field, Iran, approximately, a third of the wells have been removed from the production cycle due to casing collapse, which in some cases have led to the total loss of those wells. Since most of these cases have occurred in Gachsaran Formation, it is necessary to use an appropriate method to determine the geomechanical characteristics of this formation, especially, the layer considered as caprock for the underlain Asmari reservoir under the real conditions of temperature and pressure at real depths. In this paper, after discussing the effect of temperature, loading rate, and confining pressure on general geomechanical behavior of rocks, and in particular, the caprock of the Asmari reservoir, the results of geomechanical experiments performed under different temperature and pressure conditions on this type of rock are presented, and their comparison with the corresponding results determined by other researchers are discussed. The obtained results from the experiments demonstrate that under constant loading rate, each 1.0 MPA increase in confining pressure increases the strength of the caprock about 1.0 MPa. Conversely, every 1 °C increase in temperature decreases the caprock strength almost 0.2 MPa.