Hydrocarbon phase in the deep Cambrian of the Tarim Basin

The hydrocarbon phase of the deep Cambrian in the Tarim Basin is a scientific focus of geochemists and explorationists. Thermal simulations of heavy oil, normal oil and waxy-oil from the Tahe Oilfield in the Tarim Basin were carried out using a gold-tube confined system. For a frequency factor (A) of 1.78×10¹⁴s^-1, the activation energy range of C₁-C₅ gas yield of heavy oil is the widest, ranging from 56 to 66 kcal/mol, and the dominant potential is at 59 kcal/mol. In view of the ratio of oil conversion to gas, oil can be a separate phase at temperatures of 178-205℃. According to the paleo-temperatures of the Cambrian wells from the Tabei, Tazhong, Tadong and Machu uplifts, four dynamic models of the Cambrian reservoir cracking were established. The paleo-oil reservoir of well Tashen1 in the Tabei Uplift can be as a separate oil phase above Builtup Ⅰ in the Cambrian at present, whereas only condensate oil phase existsat the bottom of the UpliftⅠ. The models of the Cambrian paleo-oil reservoirs of typical wells from the Bachu Uplift, Tazhong Uplift and Tadong Uplift suggest that the hydrocarbon phase of the above areas may be dominated by gas and condensate phases.