Reservoir Characterization Of Triassic TII Oil Group In Well Area No3 In Lunnan Oilfield

After more than 30 years of efficient development,Lunnan Oilfield has fully entered the secondary development.TII oil group in Lunnan 3 well area is the main reservoir in this area.At present,it is generally high waterflooded,and the description accuracy of the internal details of the reservoir needs to be further improved.At the same time,due to the unclear understanding of the non-main layer and insufficient productivity contribution,the pressure of stable production of the oilfield is large.Based on the 3D seismic data of Lunnan area and guided by the theories of petroleum geology,sequence stratigraphy and seismic sedimentology,this paper systematically studies the thin sand body of target layer from the aspects of sedimentary model,sedimentary main controlling factors and reservoir characterization.Firstly,the detailed characteristics of reservoir faults are finely described by using the identification technology of low-order faults under low SNR conditions,and the important influence of fine faults on the internal pattern of reservoirs is clarified.Secondly,the fine sequence division combined with the analysis of sedimentary model clarified the favorable conditions for lithologic accumulation of thin sand bodies in the water advance period.Based on the paleogeomorphology restoration technology of well-seismic matching,the sedimentary microgeomorphology of TII0 sublayer was restored more accurately.Combined with drilling,logging and lithologic data,the sedimentary facies belt was analyzed,and its control effect on the deposition of TII0 sublayer was discussed.The waveform inversion technology of sedimentary microgeomorphology control was innovatively formed,which accurately characterized the spatial distribution range of TII0sublayer.Finally,the favorable targets are analyzed and optimized based on the understanding of structure,reservoir formation,reservoir and oil and gas.The following results were achieved:(1)The fault development in the study area has obvious inheritance relationship, and there are mainly four types of faults,among which the NE strike-slip fault has obvious control effect on the internal pattern of the reservoir;(2)The thin sand layer No.0 of TII oil group under the background of water inflow in the study area belongs to the beach bar sand body of shore-shallow lake.The sedimentary micro-geomorphology of this set of thin sand body is generally distributed in multiple rows,which is the main control factor for the deposition of TII0 layer.The TII0 layer is developed in the groove position of micro-paleogeomorphology;(3)Waveform inversion constrained by sedimentary microgeomorphology accurately characterizes the spatial distribution characteristics of TII0 layer with thickness of only 1-3 m.The predicted results are in line with sedimentary understanding and have high degree of well coincidence;(4)The structural traps of the Neogene Jidike Formation in the study area were formed in the southern Triassic before deposition,which matched the Paleogene-Cretaceous hydrocarbon expulsion phase and formed the paleoreservoir;adjusted in the middle and late Kuqa Formation,the distribution of potential areas is mainly controlled by the EW-trending paleotectonic belt and the NNE-trending hydrocarbon migration path;(5)Thirteen new lithologic traps with a total area of 96.34 km~2 and a predicted resource of 1224×10~4t have been discovered based on the study of structure,fault,reservoir and hydrocarbon migration.