Keywords: 
• Diagenetic Sequences /
• Physicochemistry /
• Thermodynamics.Reaction Gibbs Energy

Abstract: During sediments to be overlaid, a series of geological events occured.Especially when the underground water took partal, they become very complex.In these events, a large amount of minerals generated or converted and some minerals or elastics dissolved, which resulted in lots of secondary pores generation.It is not only important to improve the properties of reservior rock, but also to form diagenetic trap.Therefore, studying the complex diagenetic events is not only a Part of lithology and sedimentology, but also a part of Petroleum geology and reservior geology.In this paper, all of those geological events occured in underground environment assumed to be a series of physicochemical reactions.Those reactions alwayas follow Thermodynamic-Second Law and Third-Law.According to those assumptions, a method is derived which can be used to determine the diagenetic sequences by calculating the reaction Gibbs energy.The method is more logical and more reliable than the traditional method by which the sequences are determined use of identifying the concocts and shapes of secondary minerals.At last this method is verified by two examples which are from two models of oil fields (China and American).This poper presents a good demonstration for how to research reservior rock development history quantitatively.