DISTRIBUTION AND SEDIMENTARY FACIES OF MESOZOIC MAIN TARGET STRATA IN SOUTH TIDAL LAND OF HUANGHUA DEPRESSION

We discuss the stratigraphic division and study the distribution characteristic of Mesozoic of the south tidal land in Huanghua depression by using logging and seismic data. Then we probe into the lithofacies,logging facies and seismic facies of the Mesozoic strata. On the basis of these researches,we study the facies and sub-facies of the Mesozoic main target strata. Distributions of Mesozoic are mainly controlled by Indo-China SN extrusion, Yanshan SE-NW extrusion and Cenozoic dextral pull-dispartment. J_1-2 is distributed only in low-lying multi-anticline in the north zone,and is absent in south zone of the research area. The long axes of the residual Mesozoic strata are EW trending. Triassic is distributed in the south zone,centralizing and concealed in Paleozoic anticline with EW trending. The depo-center of J_1-2 is close to the east section and the residual depth of Mesozoic is incrassate from circumambiency to the deposit-center. The Mesozoic main target strata are lower-Jurassic which is of meander river facies formed in humid-, semi-humid weather condition. Meander river facies can be divided into stream channel sub-facies and alluvial flat sub-facies. The fabric and constituent maturity of conglomerate of stream channel sub-facies is fine, and so can act as reservoir,while the alluvial flat sub-facies is fine sediments and can be cap rock.