EFFECT OF CYCLIC FORMATION PRESSURE CHANGES ON PERMEABILITY.

Unconsolidated sand cores of various mesh sizes were subjected to repeated pressurization-depressurization cycles; absolute and relative permeabilities were measured during the low-pressure cycles. The core permeabilities decreased due to the pressurization of the core. The permeability continued to decrease, with successive pressurization-depressurization cycles, at a decreasing rate of reduction. The number of cycles after which no further reduction in permeability occurred decreased with increasing the cycle duration. Some recovery in permeability was achieved when the core was left at low pressure for a long time; however, the core was permanently damaged.