Shiyou shiyan dizhi (Jan 2020)
Mechanism of “high-speed braking” effect on heavy oil formation during hydrocarbon migration: a case study of the eastern part of southern slope of Dongying Sag, Bohai Bay Basin
Abstract
The phenomenon of "high-speed braking" occurs due to the accumulation of oil and gas during hydrocarbon migration. Then the macromolecular substances are blocked and cannot pass through, while the small molecules can continue to migrate. The well Wang 146 area is located in the eastern part of the southern slope of the Dongying Sag in the Bohai Bay Basin. The viscosity of crude oil in the fourth member of the Shahejie Formation in this area is higher than that of the Dingjiawuzi structural belt in the lower part and the Bamianhe structural belt in the higher part. The "high-speed braking" effect was used to explain the occurrence of this phenomenon, and the formation mechanism of ultra-heavy oil reservoirs in this area was analyzed. At the same time, the geological conditions for the formation of the "brake effect" were discussed from three aspects: sand body thickness, formation inclination, and the characteristics of abnormal formation pressure. The differences in the main peak carbon, ∑C21-/∑C22+, and the degree of crude oil degradation in the three tectonic belts of the study area can be used as favorable geochemical evidence for the formation of heavy oil caused by the "high-speed braking" effect during crude oil migration.
Keywords
