Relationship Between Hydrothermal Fluid Activity And Reservoir In Fault Zone 4 At The Shunnan Area Of Tarim Basin

With an area of approximately 560,000 km²,the Tarim Basin is the largest petroleum-bearing basin in China.In recent years,the SN4 well,the SN401 well and the SN4-1 well have been drilled at the SN4 fault zone in Tazhong,but the oil and gas production of the three wells is different.This article uses core observation,rock petrographic observation,inclusion micro-thermometry,laser Raman test,carbon and oxygen isotope test and other research methods to compare the three wells in the SN4fault zone.By the study,the relationship between the hydrothermal fluid activity widely existing in the area and the reservoir is obtained.?1?Core observations revealed that the hydrothermal effect of Well SN4 is strong,with a large number of fractures and pores,and a small number of fractures were filled with calcite or quartz;the hydrothermal effect of Well SN401 is weak,with a small number of fractures and pores,and most of the fractures were filled with quartz or calcite;the hydrothermal effect of Well SN4-1 is the weakest,with only a few fractures,and most of them were filled by calcite.According to the statistics of core fractures,the density of core fractures in the three wells differs greatly,and they decrease in the order of Well SN4,Well SN 401,and Well SN4-1.Hydrothermal fluids have advantages and disadvantages for reservoir reform.?2?Observation under the core slice of Well SN401 revealed that quartz and calcite were developed in sequence from the fracture wall outwards.We have got the result of the inclusion micro-thermometry.The homogenization temperature range of inclusions developing in quartz developing in fractures of silicified carbonates is 121.7-191.7??average 152.2??,and the salinity range is 14.16-23.69wt%NaCl+CaCl₂?average 22.69wt%NaCl+CaCl₂?;the homogenization temperature range of inclusions developed in calcite developing in fractures of silicified carbonates is 128.9-172.5??average 147.83??,and the salinity range is 16.70-22.69wt%NaCl+CaCl₂?Average 18.67 wt%NaCl+CaCl₂?;the homogenization temperature range of inclusions developed in calcite filled in the fractures of weak silicified limestone is 128.50-158.00??average 139.63??,and the salinity range is 17.94-24.46wt%NaCl+CaCl₂?Average 22.31 wt%NaCl+CaCl₂?.So the silica-bearing hydrothermal fluid has the characteristic of high temperature/low salinity,indicating that the original silica-bearing hydrothermal fluid from the deep is not high in salinity.?3?The paleopressure recovery results show that the trapping pressure distribution range of the inclusions developing in quartz developing in fractures of silicified carbonates,Well SN401,is 47.09-113.25MPa.Combined with the burial history and thermal history map of the Shunnan region.It was found that the hydrothermal activity of Well SN 401 happened in the Late Triassic,which was related to the fault activity of the late Hercynian.The range of?¹³C_VPDB of the detrital calcite in Well SN 401 is-2.20-0.50‰,with an average of-1.09‰;the range of?¹⁸O_VPDB is-9.30--7.20‰,with an average of-8.24‰.As the content of detrital quartz increases,the values of?¹⁸O_VPDBPDB of the detrital calcite also slowly become negative.