Research On Sedimentary Facies Of Yanchang Formation Of Chang-6 Oil Formation In Hujianshan-Wuqi Region

Applied with field profile observation, core description, logging data interpretation, thin section identification, reservoir lithology and physical property analysis, and some effective theories of other subjects such as sedimentology, lithofacies-paleogeography, reservoir geology, and sequence stratigraphy, the sedimentary facies of Chang-6 oil formation of the Triassic Yanchang Formation of Hujianshan-Wuqi region was studied deeply.By the primary marks of contrast in region, data of reconnaissance in field and interface of sequence stratigraphy, stratum of the oil-containing interval Chang-6 oil formation of Yanchang Formation were devised. Based on the tectonic movement surface, super long-term base level cycles are marked off. All the sequence interfaces are identified from logging profiles, including sequence boundaries, maximum flooding surface, first flooding surface, subsequences and subsequence sets; meanwhile, identified and classified system tracts and datum level cycles. From all the work above, Yanchang Formation are divided into a tectonic supersequence and five pieces of third class sedimentary sequences, which are compared with traditional stratum partition.This paper investigated source of Chang-6 oil formation in Hujianshan-Wuqi region, by the study of the regional geology, palaeocurrent direction, light and heavy mineral debris analysis, CLM, trace element and REE analysis as well as ancient land distribution feature. These make sure that NE is the main direction of sediment provenance, and that metamorphic rock of Archeozoic Jining Group, Wulashan Group and lower Proterozoic Erdaowa Group in Daqing Mountain and Yinshan Mountain in the north and northeast part of Ordos Basin.According to outcrop observation, core description, single well log facies analysis and connecting-well section comparison, combining with the rock types, depositional texture, structure characteristics, paleontology, litho-electric features, profile structures and sedimentary cycles, etc. It shows that Chang-6 oil formation of Yanchang Formation is composed of the lacustrine system and the delta system in Hujianshan-Wuqi region, which are subdivided carefully into 4 subfacies and 13 microfacies.The sedimentary micro-facies and sandstone distribution character of Chang-6 oil formation in Hujianshan-Wuqi region is displayed for the first time by this thesis. Considering that subaqueous distributary channels in deltaic front microfacies and delta plain microfacies are the main frame sandbodies for oil and gas reservoir. The distribution rule of sandbodies is determined by sedimentary facies. Sedimentary environments of Chang-6₁, 6₂, and 6₃ subages have good inheritance, which make all the sandbodies of different time spreading in the NE direction on the whole, and are obviously influenced by denivellation. Chang-6₃ subages are lacustrine ingression, Chang-6₂ and Chang-6₁ subages are hold in line. Combining the distribution of sandbodies with several factor analysis of reservoir control factors, enrichment regularity and reservoirs type, etc, favorable exploration areas of the main Chang-6 oil formation in Hujianshan-Wuqi region are selected out in the end.