A Three-dimensional Numerical Sedimentary Simulation Model For The Lower-middle Ordovician Of Shunnan Area, Tarim Basin

The Central upgift is in the central of Tarim Basin, it’s a long development inherited palaeo-uplift. It locates in the downthrown block of Tazhong No.1 slope-break zone. It’s a monocline which is southeast to the northwest.From the analysis of seismic data and core data in the study area,Tazhong area’s lower-middle Ordovician Penglaiba Formation-Yijianfang Formation can be identified five third-order sequences.Through well position calibration recognition,T78 is the top of the Penglaiba Formation、T76 is the top of the Yingshan Formation、T74 is the top of the Yijianfang Formation.The numerical sedimentary forward simulation in lower-middle Ordovician of Shunnan work area on Tazhong northern ramp of tarim basin was presented by means of Dionisos software and sedimentary facies、cores data、paleo-water depth、subsidence,etc.Based on analyzing regional geological background,tectonic evolution,sedimentary characteristicas,applying sedimentary simulation experiment method and Dionisos software as a platform, three-dimensional sedimentary evolution process of the region is reproduced by establishing the initial model、analysing the changes of the sea level,adjusting the characters of carbonate production rate and the wave’s power and direction.Through this analyzing the main factors that controls platform’s formation and evolution,discussing the distribution patterns of high-energy carbonate sedimentary environment,analyzing the exposure characteristics of the key interface,discussing the types of the sedimentary facies and sedimentary structure under the condition of laboratory in order to solve related questions.The simulation results shows that platform edge in the study area begin to form from cambrian period.The platform mostly are vertical accretion.At the same time Basin slope on the east side of the edge are continually deepening and the slope become steeper.From Cambrian period to Ordovician period the location of the platform edge has no significant change.Each sedimentary cycle are completely developed.During the time many exposed surface because of the water subsidence are emerged,including unconformity surface.T78、T76 interface performs two long-term exposed surface.Local area shows interal small-scale parallel unconformity、small angle unconformity、exposed erosion surface and so on.A series of exposed or erosion characteristics of karst cave and moniliform distribution which is shown in seismic section are formed under the intersface.During Early-Middle Ordovician, frequent short-time exposure occurred at the top of the depositional cycle in Shunnan area and resulted in the formation of vugular-pore in carbonate deposits subjected to leaching and dissolution of meteoric fresh water, which makes a change that only the fracture dominates the developing of the carbonate reservoir.