Abstract:

In order to investigate the complex accumulation model of super heavy oils in LX oilfield (Minghuazhen and Guantao formations), integrated data including geochemical, petrophysical and fluid inclusion analysis were applied in this study to reconstruct the charge history in Dongying Formation, and to characterize the evolution process of oil properties and therefore densification during the charge period. Based on the combined analysis on both the shallow braided channel reservoir and oil saturation, the accumulation processes and model of super heavy oil in shallow reservoirs were established, the result as follows: (1)The hydrocarbon accumulation in shallow Minghuazhen and Guantao formations is strongly associated with the destroy of deep Dongying  oil reservoirs. The hydrocarbon in Dongying Formation was accumulated during 28 to 25 Ma and thereafter suffered biological degradation. During the oil evolution history, the density was increased firstly and then the viscosity was increased, which reduces the oil properties and decreases the requirement to cap rock sealing capacity. The dynamic evolution processes made it possible that crude oil could accumulate in the Minghuazhen and Guangtao formations which have poor sealing capacity during 5~0 Ma. (2)The vertical cyclicity of the oil saturation and oil properties is ascribed to the vertical stacking pattern of braided channel sandy bodies in Minghuazhen and Guantao formations as well as the fact that crude oil were suffered from biological degradation during the charging time. This is corresponding to the cycles of reservoir lithology. In term of these analysis, we established the hydrocarbon charge models and characterized the vertical distribution of crude oils.

Key words: super heavy oil, source of crude oil, charge history, crude oil degradation, reservoir characteristics, LX oilfield, Liaodong Bay Depression