Effects of pore geometry and rock properties on water saturation of a carbonate reservoir

摘要

Capillary pressure analysis is an important piece of every reservoir rock study. Mercury injection capillary pressure (MICP) is one of the best methods for pore geometry analysis among different techniques for obtaining the capillary pressure data. Pore-facies analysis is a useful method for classifying the carbonate reservoir rocks directly according to their pore system characteristics using the MICP curves. One of the challenging subjects in every carbonate reservoir study is the characterization of reservoir fluids behavior in the pore network. The purpose of this study is determining the effect of the rock properties and pore geometry on water saturation in the carbonate reservoir rocks. Two types of reservoir rock classification were performed based on the MICP and air-water capillary pressure data. The results show that the reservoir rock samples with specific depositional texture, pore type and cement content show distinct capillary and water saturation behavior. Therefore, the pore geometry of rock samples has a strong effect on the fluid movements and entrapment in the reservoir rock. In turn, it is the result of depositional texture and diagenetic features. Although understanding the relationship between the rock properties and capillary behavior and determining the controlling parameters in fluid behavior in the pore network is very difficult and time consuming in carbonate reservoirs with such a complicated pore system, it is possible by detailed capillary pressure and petrographic studies.