Research On Sedimentary Facies Of Jurassic In Lunnan Area

On the basis of core observation and analysis,this article has a combination of the theory and method of sedimentogy,continental sequence stratigraphy and petrolume geology,using the information of well logging and seismic,the strata of Jurassic in Lunnan field have been carried on the detailed stratigraphic division and correlation,the identification of the type of sedimentary facies,integrated analysis of sedimentary facies and sand body distribution rule,then combine the structural feature and testing oil data to select the favorable exploration blocks.By analyzing logging curves of all wells,we totally find eight marker horizons.Under the constraints of these marker horizons,according to the multicycle feature,we divide the Jurassic into four oil groups of JI?JII?JIII and JIV,six sand groups and sixteen single sand beds.In the region of research,the Jurassic mainly developes pebbled sandstone,sandstone and mudstone,the color of sandstone is mainly gray,gray green,the color of mudstone is mainly dark gray and ash black.And the percentage of sand and mudstone presents the characteristic of “sand bag mud”.Grain size accumulation curves include the typical “two stage” and the arc arch.Sedimentary structure mainly develops block bedding,cross bedding,parallel bedding,horizontal bedding,sand grain bedding and scour surface.The logging curve includes box-type,campaniform,flat and straight section clipping flat campaniform and digitiform.Above all,we conclude that the Jurassic in the working area develops braided river delta sedimentary,the main development of sedimentary subfacie is braided river delta plain,the braided river delta front develops four sedimentary microfacies,including braided channel,flood plain,braided channel's edge and interchannel.The braided river channel of this area presents a banded and platy distribution on plane,and its trend is north to south.By analyzing several factors including structural characteristics,sedimentary facies,distribution of sand body and well testing data,in Lunnan field,it is believed that JIV1-1 and JIV1-2 are the main reservoirs in Jurassic region of Lunnan field.Sedimentary facies' distribution and structural features are the major factors controlling oil accumulation and we can select five favorable blocks.