The characteristics and influencing factors of permeability stress sensitivity of tight sandstone reservoirs

Highlights

• The permeability of tight sandstone decreases significantly with the increase of effective stress.

• The compression resistance of rock components can affect stress sensitivity of permeability.

• The microscopic pore structure is analyzed by means of SEM, CTS and HPMI.

• Permeability is significantly affected by stress in the pore structure with small pore-throat radius.

Abstract

The permeability decrease caused by the increase in effective stress notably influences the development of tight sandstone reservoirs. Therefore, it is necessary to study permeability stress sensitivity characteristics. Permeability stress sensitivity evaluation experiments of tight sandstone were conducted. On this basis, the influencing factors were analyzed by means of scanning electron microscopy (SEM), cast thin section (CTS) and high-pressure mercury intrusion (HPMI). The results show that permeability decreases with increasing effective stress and that the decreasing trend gradually slows. After the effective stress is restored, permeability cannot be fully recovered. The microscopic pore structure has an important influence on stress sensitivity. According to the characteristics of the capillary force curve, the pore structure can be divided into three types: intergranular, dissolved and micro pore types. Reservoirs of the intergranular pore type have a low permeability stress sensitivity, and permeability slightly decreases with increasing effective stress, followed by reservoirs of the dissolved pore type, and those of the micro pore type have the highest permeability stress sensitivity. In addition, petrological characteristics also influence permeability stress sensitivity. The contents of flexible lithic fragments and clay mineral interstitial material are positively correlated with reservoir permeability stress sensitivity, and those of quartz skeleton particles and siliceous interstitial material are negatively correlated with the latter. A better understanding of permeability stress sensitivity and its influencing factors can provide a reference for the development of tight sandstone reservoirs influenced by it.