The sedimentary environment and control factors of Youganwo Formation oil shale in Maoming Basin

摘要

Maoming Basin has been the second biggest producing area of oil shale which develop Youganwo formation of Paleogene System and Shangcun Formation of Neogene System.Based on the data of field outcrop and wells, the sedimentary facies marks of Youganwo formation are summarized in combination with the studies on lithology and element geochemistry.The sedimentary types are identified including shallow lacustrine facies, half deep lacustrine facies, deep lacustrine facies, limnetic facies and delta facies.And the main type of oil shale is half deep lacustrine.Combined with the characteristics of sedimentary facies, reservoir petrology , organic matter, etc, the favorable factors of high quality oil shale including the anoxic retention environment on the bottom of half deep lacustrine to deep lacustrine facies, the appropriate ancient climate conditions and deposition rate, the temperature and salinity stratification of water, the transgressive events, et al.The sedimentary basement morphology and basin tectonic evolution are the main controlling factors of stratigraphic distribution state.Two forms of oil shale in Youganwo Formation and Shangcun Formation have different enrichment pattern of organic matter.The enrichment pattern of organic matter of Youganwo Formation are benefited by reduction sedimentary environment.While Shangcun Formation is controlled by high deposition rate.Thus, the quality of oil shale in Shangcun Formation is worse than Youganwo Formation.