Study On Logging Response And Fluid Identification Method Of Tight Sandstone Gas Reservoir In Kuqa Depression

The formation pressure system in the Kuqa Depression of the Tarim Basin is complex.Under the dual effects of strong tectonic compression stress and gravity compaction,the reservoirs in this area present the characteristics of ultra-low porosity and ultra-low permeability.Affected by strong horizontal compression stress and high-steep structure,reservoir logging response characteristics are complex,the resistivity difference between gas and water layers is not obvious,it is difficult to use electrical logging to accurately evaluate reservoir fluid properties,and fluid identification is difficult.Therefore,it is of great significance to establish a set of effective fluid identification methods to improve development efficiency and accurately evaluate reservoir effectiveness.This paper takes the deep Cretaceous tight sandstone reservoir in Kuqa depression as the research object.The target interval is Bashijiqike formation.The reservoir density logging value is low,the acoustic time difference value is large,and the resistivity value range is large,generally 2-200 ?.m? From top to bottom,it can be divided into tension section,transition section and compression torsion section according to the change of resistivity.Combined with petrophysical experiments,the "four property relationship" of reservoir is analyzed,and the main controlling factors of resistivity in tension section,transition section and compression torsion section are analyzed from macro factor and micro factor.Affected by the gypsum layer at the top,the resistivity of the tensional reservoir is low,while the high resistivity of the compression torsion reservoir at the bottom is mainly related to the in-situ stress.On this basis,combined with the gas test data in the study area,the research on fluid identification methods was carried out.Taking into account the poor fluid identification accuracy of resistivity logging,three-porosity logging and array acoustic logging were used to extract fluid sensitivity factors,and a fluid identification chart was constructed.The two-porosity overlap method,based on three-porosity logging,was established respectively.Backcalculation sonic curve method,porosity difference ratio method,Lame constant method mainly based on array sonic logging,fluid compressibility method,p-s-wave velocity ratio measured value to theoretical value ratio method,DSI fluid identification factor method,etc.Kind of fluid identification plate.Counting the coincidence rate of each fluid identification plate shows that the fluid identification method based on array acoustic logging has a better application effect in the study area,and the coincidence rate is high.At the same time,in order to integrate various fluid sensitivity factors and give play to the advantages of different fluid identification methods,the Lame constant method,fluid compressibility method,and P/P wave velocity ratio method with high coincidence rate are selected.,Established a comprehensive fluid identification method,and further improved the fluid identification coincidence rate.Based on CIFlog platform,the processing module is developed and formed to realize the standardized processing and batch processing of fluid identification.In addition,through core observation and imaging logging,it was found that the reservoir in the study area developed fractures.Therefore,this paper uses electrical imaging logging and array acoustic logging to identify fractures,evaluates the effectiveness of the reservoir,and establishes a chart for the classification of reservoirs.The effectiveness of fractures was evaluated using shear wave anisotropy and Stoneley wave permeability,and it was shown that the more developed the fractures,the greater the anisotropy,and the stronger the shear wave anisotropy of unfilled fractures,and the shear wave anisotropy of filled fractures.The characteristics are weaker.the more fractures develop in the formation,the greater the permeability of Stoneley waves,the more obvious the attenuation of Stoneley waves,and the better the formation permeability.Based on the degree of fracture development and connectivity in the study area,the reservoirs in the study area were classified,and the stoneley wave permeability and fracture porosity were used to construct a reservoir classification chart,and a quantitative method for the classification of tight sandstone reservoirs in the study area was established.