Advance in alkaline dissolution of sandstone

Abstract

Alkaline authigenic minerals such as chlorite, laumontite, albite, and illite formed by alkaline dissolution of volcanic materials and feldspar are the focus of sandstone reservoir research, but alkaline dissolution itself is often ignored. Through analysis of the alkaline dissolution mechanism, controlling factors and diagenetic characteristics, it is found that alkaline dissolution includes five types: alkaline dissolution of quartz grains, hydrolysis and dissolution of volcanic materials, K-feldspar dissolution caused by illitization of montmorillonite, K-feldspar dissolution caused by illitization of kaolinite, and albitization of plagioclase. As alkaline dissolution is often superimposed with acid dissolution, it is difficult to directly determine the type and scale of alkaline dissolution and is often ignored or misjudged as acid dissolution. Based on the genetic relationship between alkaline dissolution and its associated cements, the type and scale of alkaline dissolution of some sandstone reservoirs are analyzed. Alkaline dissolution is very common in the petroliferous basin of China, and the secondary pores formed by the first four kinds of alkaline dissolution can reach 2%-7%, 5%-10%, 1.32% and 1.63%, respectively.

Keywords

• alkaline dissolution
• diagenesis
• secondary porosity
• hydrolysis of volcanic materials
• illitization of montmorillonite