Study On Architecture And Connectivity Of The Fourth Member Of Jurassic Sand Bodies In Lunnan Area Of Tarim Basin

Lunnan Oilfield is located at the northern part of Tarim Basin.The main focus of this study is J? Member,which depositional system is braided stream.Sand bodies are stacked in multiple phases,and sand body connectivity is complicated.This study carries out an anatomy of the internal architecture of the sandstone reservoir within J? Member,though integrated methods of hierarchical and pattern analyses.This study also quantitatively characterize different sandstone bodies in several hierarchical orders,in order to further understand the controlling factors of the reservoir connectivity and map the connectivity.Based on the above methods,following results are achieved.(1)The J? Member can be subdivided into three oil-bearing units,as J?1,J?2,and J?3,and 8 sandstone layers.(2)The entire J? Member is composed of braided stream deposits.By using the Google Earth software to measure the modern sedimentary outcrops and establishing the geological knowledge base,combined with the anatomical results of the well network pattern to establish the sedimentary facies model of the study area.It is found that the length of the channel bar in the study area is 1100?3200m;the width of the channel bar is 300?600m;the thickness of the single channel bar is 2?8m;the aspect ratio is about 1:2.(3)Sixth orders of the surfaces are identified,on the basis of the aforementioned architectural analyses and former studies.The third-order surface can be characterized in single well.The main architecture units in the study area are channel bars and braided channel sand bodies.Some small-scale floodplain mudstones exist as interlayers.The channel bar is the most important type of configuration unit.The profile form of channel bar is �bottom flat top convex�.The thickness of a single channel bar is several meters to ten meters,and the thickness of complex channel bar can reach 20?45m.The thickness of the braided channel sand body is several meters to twenty meters.The floodplain mudstone formation between the different periods of channel bar and braided channel sand body is a mudstone configuration unit that acts as a barrier in the reservoir,with a thickness ranging from one meter to several meters.(4)The connectivity of sand bodies are mainly affected by the development of sand forming period and stratum stratification,and sedimentary type.It has the bridge type of the same sand body channel corresponding to the channel bar,and the vertical sand body and channel bar superposition of different stages,and the composite sand body connectivity mode.(5)Under the control of sedimentary facies,based on the study of configuration,and combined with the tectonic characteristics,analyzing the Jurassic oil and gas accumulation in Lunnan area,the J?1 oil-bearing unit is considered to be the main reservoir area,and 4favorable reservoir forming areas are predicted in the study area.