## 5 Discussion
### Influence Factors of Micro-Sealing Ability  
In order to clarify the reasons for the significant difference in breakthrough pressure of the samples, core data and thin sections corresponding to different breakthrough pressures in wells ZS 5 and Y 10 were selected. It was found that apart from permeability, fractures have a significant impact on breakthrough-pressure results (Figure 11). In Figure 11, three thin sections with increasing breakthrough pressure in well ZS 5 are shown. The lithology includes gypsum dolomite, dolomicite and powder crystal dolomite. As shown in the figures, when there are unfilled structural fractures, it will cause higher permeability  
Figure 10: Isopach map of Cambrian gypsum-salt rocks and basin tectonic units in the Tarim Basin.  
and lower breakthrough pressure, while conversely, it will cause lower permeability and higher breakthrough pressure. The dolomicrite in well Y 10 also has the same characteristics. From Figure 11d, it can be seen that multiple structural fractures have developed, with a breakthrough pressure of only 0.7 MPa. In Figure 11e, the fractures are filled with calcite and dolomite, with a breakthrough pressure of 4.5 MPa. However, in Figure 11f, there are no fractures, with a breakthrough pressure of 11.5 MPa. Therefore, fractures will reduce the breakthrough pressure of rocks and affect their sealing performance.  
Through microscopic analysis of the sealing property of the Middle Cambrian samples, it was found that, compared to carbonate rocks, the breakthrough pressure of gypsum varies significantly, and many of the rocks have higher porosity and permeability. This contradicts the understanding that gypsum can be used as a high-quality caprock. In response to this problem, [PERSON] et al. [31] conducted triaxial stress tests on gypsum samples of the Middle Cambrian in the Tarim Platform Area and they believe that gypsum is prone to cracks and fractures when buried at depths above 650-700 m, leading to loss  
Figure 11: Typical microscopic characteristics of the Middle Cambrian (Shayilike Formation and Awatage Formation) samples in the Tarim Basin (monopolar light). **(a)**—Well ZS 5, Shayilike Formation, gypsum-Well ZS 5, Shayilike Formation, gypsum-Well ZS 5, Awardage Formation, anhydrite dolomite; **(d)**—Well Y 10, Awardage Formation, argillaceous dolomite; **(e)**—Well Y 10, Awardage Formation, argillaceous dolomite; **(f)**—Well Y 10, Awardage Formation, argillaceous dolomite.  
of sealing capacity. After burial depth exceeds 700 m, gypsum transforms from brittle to plastic, and its sealing ability is strongest. When the layer temperature exceeds 52 \({}^{\circ}\)C, gypsum begins to dehydrate and transform into anhydrite, forming a large number of pores, and the sealing ability decreases at this time. When the burial depth of anhydrite reaches 3300 m or more (this depth corresponds to the boundary pressure of brittle-plastic transformation), anhydrite regains plasticity. At the same time, the compaction effect also reduces the pores inside the gypsum, making it regain its sealing ability. This provides a basis for quantitative evaluation of gypsum sealing property of the Middle Cambrian in the Tarim Platform area [43].