NEW IDENTIFICATION METHOD OF LOW-PERMEABILITY RESERVOIR DIAGENETIC FACIES

Quantitative characterization of diagenetic facies has great significance for reservoir evaluation and prediction. In order to find methods of quantitative classification of diagenetic facies, chang 8¹ reservoir of Yanwu area in ordos basin has been taken as researching object, and diagenetic facies are characterized quantitatively by data envelopment analysis method, during which 14 quantitative evaluating parameters of diagenetic facies have been chosen, such as petrology characteristic parameter, diagenetic strength, porosity, etc. The results show that quantitative characterized index of diagenetic facies in chang 8¹ reservoir of Yanwu area ranged between 0 and 1. Quantitative characterized index of diagenetic facies is related with each diagenetic facies regionally. It's positively correlated with absorption strength and negatively correlated with remaining oil saturation. Chang 8¹ oil reservoir group of Yanwu area in ordos basin is divided into constructive and destructive diagenetic facies. Constructive diagenetic facies includes the diagenetic facies of weak corrosion with chlorite mat and diagenetic facies of weak corrosion of unstable components, while destructive diagenetic facies includes the diagenetic facies of clay mineral cementation-replacement, the diagenetic facies of quartz secondary enlargement, the diagenetic facies of filling with kaolinite and the diagenetic facies of carbonate cementation. Using data envelopment analysis method to calculate characterization indexes of diagenetic facies effectively overcomes the defects of giving weights factitiously and avoids tedious process of dimensionalizing parameters when each parameter is calculated in indexes of diagenetic facies comprehensive characterization. We can calculate diagenetic facies indexes of reservoirs by quantitative evaluation of diagenetic facies. The relationships among diagenetic facies indexes, absorption strength and remaining oil saturation can be used to evaluate the quality of reservoirs. When diagenetic facies indexes range between 1 and 0.60, they have stronger absorption strength, higher flushing efficiency and smaller remaining oil saturation.