## 2 The Overview of the Study Region  
The Southwest Depression of the Tarim Basin, situated in the southwestern part of the basin, is bordered by the South Tianshan orogenic belt to the north and the West Kunlun orogenic belt to the south. Encompassing an area of approximately 100 \(\times\) 100 km\({}^{2}\), it is the largest sub-basin within the Tarim Basin and a favorable area for oil and gas exploration in Cambrian Ordovician carbonate rocks. The traps formed during the Himalayan movement predominantly consist of effective hydrocarbon source rocks distributed in the Bachu fault uplift and Maigait slope area ([PERSON] et al., 2000) [20]. After extensive research, a consensus has emerged concerning the Cambrian subsalt of the Maigait slope: the Maigaiti slope contains Ordovician Carboniferous oil and gas sources, while drilling through the Cambrian south of Bachu revealed no Cambrian source rock, indicating the development of Cambrian subsalt source rock in the slope area. The Middle-Lower Cambrian serves as an important reservoir and regional cap rock for the area's deep carbonate rocks and is a significant horizon for hydrocarbon source rock development ([PERSON] et al., 2017; [PERSON] et al., 2015) [21; 22]. Its seismic sequence features three strong reflective interfaces within the Middle Cambrian. The energy at the bottom boundary of the Lower Cambrian is not strong, whereas the bottom of the upper salt section displays a continuous and stable strong wave crest. A noticeable phase change occurs at the bottom of the lower salt section, and the sedimentary pattern from the Early Cambrian to Middle Cambrian exhibits significant changes. The three strong reflective interfaces in the Middle Cambrian provide favorable conditions for internal multiple formations. However, internal multiples can distort seismic waveforms, decrease the signal-to-noise ratio, and affect effective wave identification, thereby complicating seismic processing, diminishing seismic imaging authenticity and reliability, influencing hydrocarbon source rock studies, and increasing the difficulty of oil and gas exploration and development in the northwest region. To better understand and identify the internal multiples in the study area, well-seismic calibration was performed using existing seismic and logging information, as illustrated in Figure 1. The well-seismic calibration results reveal that the bottom interface of the upper salt section at the Middle Cambrian is stable. The lithology of the lower salt section of the Middle Cambrian comprises pure gypsum salt rock with a strong wave crest at the bottom, while the lower salt section contains gypsum-bearing dolomite and exhibits a trough at the bottom boundary. The bottom boundary of the Lower Cambrian primarily appears as a trough, and the time thickness of the Lower Cambrian varies significantly across different drilling wells, as does the mismatch between well synthetic records and seismic records. Subsequently, velocity spectra were generated for multiple identification and confirmation, as depicted in Figure 2. Figure 2 displays the velocity spectra of two distinct CMP gathers, revealing numerous low-velocity energy clusters. Following NMO correction of CMP gathers using primary velocity, downward-bending events indicate the presence of a large number of multiples in the original seismic data, necessitating multiple suppression processing. Considering the characteristics of multiples in the study area, we initially employed the Radon transform to suppress internal multiples in the pre-stack data. However, the Radon transform cannot entirely eliminate all internal multiples present in the data, and this method can only suppress some long-period multiples. Multiples interference still exists under the Cambrian salt, as shown by the red circle in the velocity spectrum in Figure 3. Additionally, there are significant differences in energy and frequency of multiples in the  
Figure 1: Well A synthetic record calibration and well seismic profile. horizontal direction.