## 4 Gas Generation Potential
### Hydrocarbon Generation Simulation
The values of the gas generation intensity of the Fengcheng Formation source rocks reaches 20 \(\times\) 10\({}^{8}\) m\({}^{3}\)/km\({}^{2}\) at 425 \({}^{\circ}\)C (Figure 6), meaning that the gas generation intensity of the Fengcheng Formation source rocks could reach the essential condition of large and medium-sized gas fields at 425 \({}^{\circ}\)C. The gas generation intensity calculation was based on the rock density of 2.5 g/cm\({}^{3}\) and the average source rock thickness of 150 m.  
The vitrinite reflectance (R\({}_{\rm o}\)) of source rock samples at each simulated temperature point was measured during the hydrocarbon generation simulation experiment, and the R\({}_{\rm o}\) corresponding to 425 \({}^{\circ}\)C was about 1.45%. The relationship between the gas generation intensity and burial depth of source rock was deduced according to the relationship between R\({}_{\rm o}\) and burial depth. In general, the relationship between R\({}_{\rm o}\) and burial depth is exponential. With the increase in depth, the growth rate of R\({}_{\rm o}\) gradually slows down [25]. It is indicated that the R\({}_{\rm o}\) at abnormally high pressure does not match its thermal history and is lower than that under the normal pressure condition (Figure 7). Previous studies have shown that overpressure may retard the evolution of organic matter and suppress the increase of R\({}_{\rm o}\). According to the statistics of the pressure coefficient variation with depth in the western part of the basin, it is evident that the pressure coefficient at 4000 m is more than 1.2, indicating abnormal high pressure (Figure 7a). There are apparent differences in the degree of abnormal development in different regions. The pressure coefficient of the Well MS 1 is higher, with a pressure coefficient of more than 2, which is close to the rock breakdown pressure, and may be the maximum pressure that could be developed. The degree of abnormal pressure development in the Well DT 1 is relatively lower, with a pressure coefficient distributed in the range of 1.2-1.35. Considering that most of the pressure coefficients deeper than 4000 m are above 1.2, it could be assumed that the pressure development of Well DT 1 is the lowest in the study area. The overpressure retardation of organic matter maturation is evident, with its depth exceeding 4000 m (Figure 7b). The higher the overpressure, the stronger the effect on the retardation of organic matter maturation. Thus in Well MS1, with the highest overpressure, the pressure coefficient is 2.0; it could be deduced that for a depth of 7000 m, the predicted R\({}_{\rm o}\) is 1.45%. Taking Well DT1 with the weakest overpressure, the pressure coefficient is between 1 and 1.5, and the predicted R\({}_{\rm o}\) is 1.45% at the depth of 6000 m. Therefore, it could be concluded that when the average burial depth is than over 6500 m, the R\({}_{\rm o}\) of the Fengcheng Formation source rock is about 1.45%, and the gas generation intensity can reach 20 \(\times\) 10\({}^{8}\) m\({}^{3}\)/km\({}^{2}\). Figure 6: Hydrocarbon producing rate and gas generation intensity of the Fengcheng Formation.