Petrophysical static rock typing for carbonate reservoirs based on mercury injection capillary pressure curves using principal component analysis

Abstract

Rock typing lay the profound basis of rational and efficient development of oil and gas reservoirs. In carbonate reservoirs, however, the identification of petrophysical static rock type (PSRT) has always been a great challenge to reservoir engineers and geologists due to its strong heterogeneity arising from the diagenetic process. The objective of this study was to propose a new method for petrophysical static rock typing in carbonate reservoirs. First, the evaluation equation of mercury injection capillary pressure (MICP) curve was established based on parameters analysis, and parameters weight was assigned by using the entropy method. Then, by analyzing and selecting the key influential parameters regarding the PSRTs in carbonate reservoirs, the novel rock typing model was established by principal component analysis (PCA) and ordinary least square (OLS) method. Finally, a realistic field case in Mishrif formation was presented through comparing the results from the proposed model with that of the existing methods, such as Winland plot (r35), flow zone indicator (FZI), FZI-star (FZI*) as well as bulk volume water method (BVW). The results indicated that the PSRTs identified by the new proposed model were superior to the others. What is reflected in the proposed model is that this approach can directly identify the PSRTs of the target formation. In contrast, neither the method of FZI nor the r35 can independently identify the PSRTs of carbonate reservoirs, they have to work jointly to determine the PSRTs.