Multivariate geochemical and statistical methods applied to assessment of organic matter potentiality and its correlation with hydrocarbon maturity parameters (Case study: Safir-1x well, North Western Desert, Egypt)

摘要

The TOC-Rock–Eval pyrolysis and vitrinite reflectance measurements for “15” shale rock samples, as well as, multivariate statistical analysis are discussed to investigate hydrocarbon, source rock characteristics, correlation between the assessed parameters (S1, S2, HI, S1+S2, QI, BI, PI, TOC) and the impact of changes in the T max and Ro% on the assessed parameters in Safir exploratory-1x well in Safir oilfield. The geochemical analysis indicated that the Bahariya Formation is considered to be a poor source rock for oil generation with a low degree of thermal maturation in comparison with the Alam El Bueib and Khatatba Formations. However, Alam El Bueib is found to be a good source rock for oil generation with slightly higher thermal maturation. Interestingly, Khatatba Formation lies within the oil and gas generation window and shows an excellent source rock potential. Based on statistical findings of cluster and factor analysis, the source rocks in the study area are classified into two types corresponding to two different clusters. Cluster I includes Alam El Bueib and characterized by kerogen type II and II/III whereas, cluster II, characterized by kerogen type III, is subdivided into two subgroups (IIa and IIb) and represents Bahariya and Khatatba source rocks. Nonparametric tests (K-independent samples) between the dataset of 15 samples confirm that the distribution of values from respective parameters exhibits significant difference (P < 0.05) except for PI and BI. On the other hand, the nonparametric tests (2-independent samples) showed that there is no significant difference (P >0.05) in the distribution of HI and QI values indicating that both HI and QI values remain constant with increasing thermal maturity. Unlike TOC and HI, Pearson’s and linear regression analysis indicated a significant correlation between TOC and S2. Nevertheless, two different trends were observed between S1 and S2. Moreover, the Ro% and T max were found to be positively correlated. Interestingly, our study showed no significant correlation between HI, QI, BI and thermal maturity (Ro% and T max ), while, a good correlation between TOC, S2 and thermal maturity was observed.