Experimental Investigation of the Effect of Salt Precipitation on the Physical and Mechanical Properties of a Tight Sandstone

Abstract

Salt precipitation in rocks is a strongly coupled physico-chemical process, which has implications on natural gas extraction efficiency. The paper examines the effect of salt precipitation on porosity, permeability, permeability-stress sensitivity and elastic wave velocities of the rock matrix in tight sandstone with high salinity. Results show that the porosity and permeability decrease significantly after salt precipitation, and the permeability-stress sensitivity was aggravated by the salt precipitation. Following salt precipitation, the elastic wave velocities decreased significantly, the dynamic Young’s modulus of the rock decreased, and the dynamic Poisson’s ratio increased. Microstructural analysis suggests that following salt precipitation, the smaller pores and pore throats become the main seepage channels. The crystalline salt was deposited in the pores, the micro-fractures and on the surface of clay minerals, which not only reduces porosity and permeability, but contributes to the development of secondary cracks that weaken the rock matrix.