Research On Reservoir Formation Conditions Of Yanchang Formation, Triassic, In Panlong Field, Northern Region Of Shaanxi Province

With the theory of sedimentlogy and petroleum geology, by a large number of drilling, logging and various analytical data applied, taking the means of theoretical study and practical research to combine and the combination of theoretical study and practical research, research on stratum and tectonic,reservoir sedimentation and accumulation rules were taken; oil and gas distribution and accumulation model in exploration area were summarized inYanchang formation Of Triassic, in Panlong field,Ordos Basin, the Results and cognition were gain generally as follows:Research on fine structure mapping of Triassic in the study area showed that reservoir inYanchang formation of Triassic, in Panlong field is not the simple monoclinic structure but a series of tectonic uplift noses developed on mnocline dumped to west whose scale and location not only have inheritance but also differences succeed. For instance, compared with top surface structure in the oil layer Chang 4+5andchang6, the nose-shaped bulge in in the oil layer Chang 2 were developed so much.By means of analysis of lithology,sedimentary structures grain size,paleontology and logging, the sedimentary facies in the oil layer Chang 6 was mainly delta front deposition, among which the delta front subfacies deposition developed at from Chang64to Chang62 and delta plain subfacies deposition developed at Chang 61; reservoir types were mainly sandstone deposited in distributary channel; sedimentation face was succeed when the stratum of Chang 4+5 deposited, the sedimentation type was delta plain distributary channel deposition previous and back swamp deposit; the sedimentation type at Chang 2 was braided fluvial deposition and the reservoir microfacies types is channel sand dam? the sedimentation type at changl was delta plain sediments, shallow lake sediment developed in some areas.The evaluation on hydrocarbon source rocks showed that type of organic matter of dark mudstones from changl formation mainly belongs to,chang2 and chang 6 mainlyâ…¢respectively,the type Hand III take some proportion in chang4+5,chang 7mainlyâ…¡; organic matter abundance in chang 7 is highest,second is chang 4+5 and chang l,the rest is worse;ecept the mudstone in chang 7 come to maturity,the rest also immaturtity,which have little contribution to reservoir.Simultaneously,oil-source correlation confirmed the oil source all come from the Zhang-jiapan lacustrine shale in chang7,partlt from dark mudstone in chang1,chang4+5andchang6 formation.Diagenesis studies have shown that the diagenesis type of sandstone reservoir mainly compaction, cementation, metasomatism and dissolution; at the same time, diagenetic compaction and cementation in early period main reason which led to low porosity and low permeability reservoir.Reservoir enrichment rules demonstrated that the oil layer chang2 distributed in sub-formationchang21andchang22 longitudinally and horizontally distributed in the northern and middle part of the study zone,which was controlled by sedimentary facies,nose like structure,migration pathway and capping formation; the oil layer chang6 horizontally distributed in the Saze duct areas and enriched longitudinally insub-formation of chang6, secondary is sub-formationchang62andchang63 which was controlled by petroleum sources,favorable sedimentary facies,reservoir conditions,migration pathway and capping formation.