Hydrocarbon Generation, In-Source Conversion of Oil to Gas and Expulsion: Petroleum System Modeling of the Duwi Formation, Gulf of Suez, Egypt

Abstract

A multiple forward 1D modeling approach on four wells in the Abu Rudeis-Sidri oil field has been performed in accordance with the plate tectonics and crustal development of the Gulf of Suez, Egypt. The current work intends to simulate the hydrocarbon generating capability, in-source conversion of oil to gas, expulsion and adsorption (retention) of marine sulfur-rich Duwi kerogen. The integration of log responses and organic geochemistry indicate mature organic-rich intervals that have been confirmed by the 1D model. The rifting phases and its associated thermal cooling have a prominent contribution on the thermal maturation, particularly the Mio-Pliocene event. The elevated basal heat flow associated with the lithosphere thinning due to different rifting phases accelerates the thermal maturation of the high sulfur content of Duwi organic-rich interval. The pre-rift sequences are thermal insulators in contrast to the post-rift sequences of evaporites that can cool the underlying strata. Hydrocarbon generation, gas secondary cracking and expulsion are influenced by the post-rift thermal subsidence (the first and second phases). The kerogen has attained a thermal maturity level to generate liquid hydrocarbon since the Messinian (~ 5.8 Ma) and thermogenic gas secondary cracking since Zanclean (~ 3.57 Ma). The hydrocarbon generation (Early Pliocene) is related to the combination of basin burial (accompanied the first phase post-rift thermal subsidence) and the rift renewal through the Pliocene (Messinian Time Event). The gas generation is related to the second phase post-rift thermal subsidence that is accompanied by the deposition of the Post-Zeit Formation. Most of the hydrocarbons attained peak bulk generation during Pliocene (5.8 Ma), which dominated until expulsion commenced (2.52 Ma). The expulsion onset (Late Pliocene) attained subsequent to gas generation and after rift structural trap formation in Late Oligocene–Early Miocene. The expulsion onset (2.52 Ma) related mainly due to a high transformation ratio of kerogen, compaction and partly because of higher initial values of TOC (4.8%) as compared with its present-day values (3.2%). Applying the sensitivity analysis inferred that the source rock properties (HI and TOC) are not assigned as a controlling factor in the maturation process. The eroded thickness has small influence on the maturation process. In contrast, the excellent correlation (Pearson correlation coefficient = 1) supports that heat flow superimposed on the burial-related maturation.