## 4 Results
### Unconformity Sealing Evaluation
#### 4.2.2 Unconformity Sealing Evaluation--Taking Ma 131 Well Area as an Example  
According to the experimental results above, when evaluating the closure of the unconformity structure, the thickness of weathered clay layer is selected from a macro perspective, and the fracture pressure is selected as the main influencing parameter from a micro perspective. The formation fracture pressure is defined as the bottom hole fluid pressure when the formation produces hydraulic fractures or opens the original fractures. In addition to the application of fracture pressure in drilling design, it can also be used to calculate the sealing height of caprock and the ancient pressure coefficient around the target layer [24], so as to evaluate the stability of the weathered clay layer structure. The larger the fracture pressure is, the more it can suppress the development of fractures and the stronger the sealing ability of the weathered clay layer is. The core of the measured fracture pressure in the study area and its corresponding porosity were sorted out, and it was found that the fracture pressure was negatively correlated with the porosity and permeability (Figure 9). The larger the fracture pressure is, the smaller the porosity and permeability are; therefore, the oil and gas could not pass through the interval, which indirectly proved that the fracture pressure could be used as a parameter to judge the unconformity sealing. Taking the Ma 131 well area as an example, Equation (7) is applied to the calculation of fracture pressure of a typical single well in the study area, and favorable application results are obtained. Based on the calculation results of fracture pressure, the single-well reservoir, along with the roof and floor, is divided and interpreted in detail (Figure 5). In order to verify the accuracy of the fracture pressure calculated by the model, the ground breaking test results are collected for verification. Taking Well Wu 36 in the study area as an example, the maximum fracture pressure difference measured by the rock sample of  
Figure 9: Diagram of the intersection of rupture (**a**) pressure and (**b**) porosity seepage. 203 m depth is 1.8 MPa, and the fracture pressure difference calculated by the formula is 1.84 MPa, at the same depth (Figure 10). The error is small, which proves that the formula can be applied in the study area. According to the above summary of the closure evaluation index, the rupture pressure (Equation (7)) (MPa) and thickness (H), two important indicators of the sealing ability of a single well, were summarized. In order to avoid the excessive difference of the rupture pressure values between different wells affecting the evaluation, the ratio of rupture pressure to normal pore pressure, referred to as the rupture pressure gradient (FG), was proposed. According to the FG curve, it can be clearly seen that the FG values between the reservoir and the caprock are significantly different (Figure 5). The average FG value of the caprock is 2.3-2.0, and the average FG value of the reservoir is 2.0-1.8. The key wells in the Ma131 well area are connected, and an even well profile of the Ma131 well area (Figure 11) is drawn to horizontally compare the FG and the thickness of each well. It was found that the oil pool in the Ma 131 well area contains three caprocks: the mudstone in the upper part of the third member of the hundred, the thin layer of mudstone in the first member of the hundred, and the weathered clay layer under the unconformity surface of the Wuerhe Formation (Figure 11). The well connection profile of the Ma 131 well area (Figure 11) shows that thicker mudstone is developed in the Wuerhe Formation in the lower part of the Baikouquan Formation, and the fracture pressure gradient is large, which provides a good floor condition for trap in the study area.