Characteristics Of Sedimentary System Of Yingcheng Formation In Jinshan Area

Jinshan Gas Field is located in the southernmost tip of southeast slope belt of Lishu fault depression which is the pointing area for longterm oil and gas migration.The ststructure and sedimentary environment in the study area is very complicated.By observing and describing the cores,analysising LWD data and 3-D seismic data,debeloping the sequence stratigraphy and implementing the stratigraphic distribution and sedimentary system characteristics of Yingcheng in Jinshan area.By the above means of research,several conclusions can be drawn:(1)The Yingcheng Formation can be divided in four sand formations.They are Ying?,Ying?,Ying? and Ying? formation.The stratum thickness of Yingcheng Formation in Jinshan area shows the characteristics of " thick in the west,thin in the east,thick in the South and thin in the north";(2)By the research of cuttings content,heavy mineral,characteristic of sandstone percent and color of mudstone,it is found that there are two provenance areas in the west and southeast of the basin margin,the western provenance area was the main provenance in Yingcheng Formation;(3)Fan delta plain,braided river delta plain,braided river delta front can be found in Jinshan Area when Yingcheng Formation developed.At the same time,four sedimentary microfacies,namely underwater distributary channel,underwater distributary bay,inter-channel and estuary bar can be identified.The Yingcheng Formation is mainly developed in the terrestrial sedimentary environment with oxidation characteristics;(4)By the research of the distribution characteristics of provenance system and sedimentary facies of Yingcheng Formation,characteristics of sedimentary system in different periods can be confirmed.In the period of Ying?,subfacies deposits of fan delta plain developed in western steep slope zone of study area,braided river delta plain subfacies deposits developed in the eastern gentle slope zone at the same time and delta front subfacies deposits developed in the northern region;In the period of Ying?,delta plain pushed northward,a large area of delta plain subfacies deposits developed in the study area;In the period of Ying?,braided river delta front subfacial deposition retreated to the south of the basin,subfacies distribution of delta plain has been greatly reduced;In the period of Ying?,delta plain subfacies pushed northward again,the range of inner front of delta reduced which had characteristic of circular distribution.Because of effects of the tectonic activity and climate,there are some differences of distribution of sedimentary facies zones,however,delta plain-front subfacies deposits are still dominant.