The Prediction Of Reservoir Distribution Of Carboniferous Sand And Mudstone Member In Santamu Area,Basin

Sangtamu is an important oil&gas-bearing area in Tabei of Tarim Basin.The sand and mudstone member of Kalashayi formation in Carboniferous system is the primary potential strata of petroleum.The results of previous rounds of study have provided a basic understanding of the sequence stratigraphy and sedimentary facies of Santamu area.However,the accuracy of sequence division does not meet the requirements of current oil and gas exploration due to the rapidly horizontal variation of sandstone in sand and mudstone member and the thinner thickness of single sand body.Therefore,it is necessary to further study the sequence stratigraphy and sedimentary reservoirs in combination with the previous research results and comprehensive utilization of the latest exploration data,thus provide a foundation for further exploration.Based on the theory of high-resolution sequence stratigraphy,the sequence division and comparison was carried out and the sequence stratigraphic framework was established on the basis of the identification and tracking of seismic sequence stratigraphic interface,logging data analysis and core observation.Taking the base-level rise-fall cycle as the mapping unit,the main sedimentary facies types,development scales and geometrical forms are summarized with the analysis of core and logging phases,and the single well sedimentary facies are described in detail,then well-tie sections are established.Subsequently,the plane distribution of sedimentary facies of sub-member unit corresponding to the sedimentary cycle was presented.Finally,the distribution of favorable reservoir of thin sand layer was presented on the basis of the understanding of sequence stratigraphy,sedimentary facies distribution,the development pattern and distribution of favorable sand bodies.The research results show that three long-term cyclical isochronous interfaces of SB1,SB2 and F1 may be identified in the study area.Four medium-term cycles of MSC1,MSC2,MSC3 and MSC4 are developed from bottom to top,which are divided into four sub-members of CK4,CK3,CK2 and CK1 respectively.The sand and mudstone member is generally developed in a delta-tidal flat sedimentary environment.The deltaic facies are mainly developed in MSC1,MSC2 and MSC3 cycles,and tidal flat in MSC4 cycle.The statistics of the porosity of the sand bodies in different sedimentary facies show the best physical properties of the sand bodies developed in the sub-facies distributary channel in delta plain and front,and the sand bodies developed in sub-facies estuary bar in delta front and tidal channels in intertidal zone of tidal flat facies are the medium,and the physical properties of the sand bodies developed in the sub-facies sand-flat in intertidal zone of tidal flat facies are the worst.The distribution of favorable sand bodies is mainly controlled by sedimentary facies,of which the favorable reservoirs in MSC1 cycle are the most developed.The reservoir in the study area can be divided into type I,II and III favorable areas,of which type I and II are favorable reservoirs.