Reservoir Characteristics and Favorable Areas of the Karamay Formation in the Mahu 446 Well District

The Karamay Formation in the Mahu 446 well district is an important oil-producing layer in the Karamay oilfield. However, the unclear characterization of favorable sandstone bodies in the Upper Karamay Formation has constrained further exploration and development in this area. This paper provides sedimentary facies distribution characteristics and seismic inversion methods to characterize the favorable sandbodies in the T₂k₂² section of the Upper Karamay Formation in the 446 well area, based on a re-understanding of the sedimentary reservoir and geophysical response characteristics of favorable sandstone bodies in the Upper Karamay Formation. The research suggests that this area belongs to a braided river delta front subfacies sedimentation, which can be mainly divided into four sedimentary microfacies: underwater distributary channels, inter-distributary bays, mouth bars, and sheet sands. The T₂k₂² section of underwater distributary channels is the most developed and is the primary favorable reservoir development section in this area. The overall provenance of the T₂k₂² section comes from the northwest, with the central channels being the most developed and having the most favorable sedimentary background. The pseudo-acoustic impedance seismic inversion method has a good effect on identifying T₂k₂² sandbodies, with the impedance boundary at 8900 g/cm³·m/s, which can identify two sets of favorable channel sandbodies with strong amplitude and high pseudo-acoustic impedance characteristics. Combining sedimentary facies distribution, seismic inversion, and structural features, this study predicts one lithological trap and its range beyond the oil-containing area controlled by the T₂k₂² section. The trap exhibits a U-shaped distribution, develops approximately 6 m of oil layer, which thins from high to low, covers an area of 8.4 km², and has a closure of approximately 300 m.