图7的左一栏为从最新钻井得到的伽马测井数据。左二栏为从纵波层速度转换来

The left column of Figure 7 is the gamma logging data obtained from the latest drilling. The second column on the left is the acoustic duration converted from the P-wave layer velocity. This curve has been corrected by the latest drilling logging data from the upper part. The purple line in the third column on the left is the stratum rock density calculated by the Gardener empirical formula method using the acoustic duration in the second column on the left. The density of the rock has been checked by the rock density parameter obtained from logging data. This shows that the layer velocity curve in the second column on the left is credible. Due to the geological history of the formation being compacted first and then uplifted, the normal compaction trend line in the second column on the left is not a straight line, but is composed of multiple line segments. The existing drilling mud has reached a depth of close to 5800 meters. Near the vertical depth of 4000 meters, the borehole wall has been severely expanded, resulting in poor logging data quality there. Near 2300 meters, there was an air invasion. <br>The right column of Figure 7 contains many curves, which makes the analysis more complicated. First of all, this column includes the curve after the numerical solution of the numerical solution of the three-dimensional in-situ stress field in the Tugulu anticline block on the Letan 1 well site is converted into the stress gradient form. Among them are the normal stress/overburden pressure along the Z-axis-3D_overburden pressure and 3D_minimum horizontal principal stress. The theoretical value of the pore pressure calculated according to the acoustic time-length curve and the overburden pressure 3D_overburden pressure is a light green curve. The empirical value of the pore pressure is the predicted value of pore pressure based on the theoretical pore pressure curve, combined with previous experience and actual drilling information from the upper part. <br>The collapse pressure SFG obtained from the numerical solution of the acoustic curve and the three-dimensional principal stress is the red curve in the right column of Figure 7. In some formations, due to the relatively high values ​​of strength parameters such as the friction angle and bond strength of the formation calculated from acoustic waves, the calculated collapse pressure is less than the pore pressure value. The lower limit value of the mud density window at such a depth section will take the value of the pore pressure. The upper limit of the mud density window is the smaller of 3D_minimum horizontal principal stress curve and 3D_overburden pressure. This shows that the three-dimensional numerical solution of ground stress can automatically and accurately select the minimum principal stress component as the upper limit of the mud window under different stress states. However, single-well geomechanical analysis is difficult to achieve this. This is one of the advantages of using the numerical solution of the three-dimensional in-situ stress field to calculate the mud density window.<br>The change trend of the pore pressure curve in the right column of Fig. 7 is: the uppermost Shawan Formation is at normal pressure. After entering the Anji Haihe Formation, the pressure coefficient rapidly increases to a high pressure above 1.8, and then in the Ziniquanzi Formation and Donggou Formation. It gradually decreased to about 1.5, and then gradually increased to a high pressure of about 2.5 in the Lianmuqin and Shengjinkou formations. The pressure coefficient decreased in the Hutubihe Formation, increased in the Qingshuihe Formation, and decreased in the Kalazha Formation, and its value remained between 2.2-2.4. Since the overburden pressure curve in the figure is obviously lower than the value of the actual drilling mud curve, it indicates that the overburden pressure of the rock at a depth below 4400 meters in this well is greatly affected by the local structure. This phenomenon illustrates the three-dimensional in-situ stress field. The necessity and importance of analysis.

The left column of Figure 7 shows the gamma logging data obtained from the latest drilling. The second column on the left shows the acoustic duration converted from P-wave interval velocity, which has been corrected by the latest drilling and logging data at the upper part. The purple line in the left third column is the formation rock density calculated by gardener's empirical formula method using the acoustic time in the left second column. The rock density has been checked by the rock density parameters obtained from logging data. This shows that the layer velocity curve in the left second column is credible. Due to the geological history of compaction before uplift, the normal compaction trend line in the left second column is not a straight line, but composed of multiple line segments. At present, the actual drilling mud has reached a depth of nearly 5800m. Near the vertical depth of 4000 meters, the borehole wall expands seriously, resulting in poor logging data quality. There was a gas invasion near 2300m.<br>The right column of Figure 7 contains many curves, which are complex to analyze. Firstly, this column includes the curve after the numerical solution of three-dimensional in-situ stress field in Tugulu anticline block is converted into the form of stress gradient at Letan 1 well location. There is normal stress along z-axis / overburden pressure-3d_ Overburden pressure and 3D_ Minimum horizontal principal stress. According to acoustic time curve and overburden pressure 3D_ The theoretical value of pore pressure calculated by overburden pressure is a light green curve. The empirical value of pore pressure is the predicted value of pore pressure based on the theoretical value curve of pore pressure, combined with previous experience and the actual drilling information in the upper part.<br>The collapse pressure SFG obtained from the acoustic curve and the three-dimensional principal stress numerical solution curve is the red curve in the right column of Fig. 7. In some formations, the calculated collapse pressure is less than the pore pressure because the strength parameters such as internal friction angle and bond strength calculated from acoustic wave are relatively high. The lower limit of mud density window on such depth section will take the value of pore pressure. The upper limit of mud density window is 3D_ Minimum horizontal principal stress curve and 3D_ The lesser of the overburden pressures. This shows that the three-dimensional in-situ stress numerical solution can automatically and accurately select the minimum principal stress component as the upper limit of the mud window under different stress states. However, it is difficult to do this in single well geomechanical analysis. This is one of the advantages of using the numerical solution of three-dimensional in-situ stress field to calculate the mud density window.<br>The change trend of pore pressure curve in the right column of Figure 7 is: the uppermost Shawan Formation is at atmospheric pressure. After entering the stratum of Anjihaihe formation, the pressure coefficient rapidly increases to a high pressure of more than 1.8, then gradually drops to about 1.5 in Ziniquanzi formation and Donggou formation, and then gradually increases to a high pressure of about 2.5 in lianmuqin and shengjinkou formation. The pressure coefficient decreases in Hutubihe formation, increases in Qingshuihe formation and decreases in Kalaza formation, and its value remains between 2.2-2.4. The overburden pressure curve in the figure is obviously lower than the value of the actual drilling mud curve, indicating that the overburden pressure of the rock in the depth section below 4400m of the well is greatly affected by the local structure. This phenomenon shows the necessity and importance of three-dimensional in-situ stress field analysis.

The left column of Figure 7 shows the gamma logging data obtained from the latest drilling. The second column on the left shows the duration of acoustic wave converted from P-wave velocity, and this curve has been corrected by the latest drilling logging data in the upper part. The purple line in the third column on the left is the formation rock density calculated by Gardener empirical formula method with the sound wave duration in the second column on the left. The rock density has been checked by the rock density parameters obtained from logging data. This shows that the velocity curve of this layer in the second column on the left is credible. Due to the geological history of strata being compacted first and then lifted, the normal compaction trend line in the second column on the left is not a straight line, but consists of several line segments. At present, the existing actual drilling mud has reached a depth close to 5,800 meters. Near the vertical depth of 4,000 meters, the borehole wall is seriously enlarged, which leads to poor logging data quality. Near 2300 meters, there was a gas invasion event. The right column of Figure 7 contains many curves, which are complicated to analyze. First of all, this column includes the curve after the numerical solution of 3D in-situ stress field in Tugulu anticline block at Letan 1 well position is converted into stress gradient form. There are normal stress/overburden pressure along Z- axis -3D_ overburden pressure and 3D_ minimum horizontal principal stress. The theoretical value of pore pressure calculated according to the acoustic time curve and overlying strata pressure 3D_ overlying pressure is a light green curve. The empirical value of pore pressure is the predicted value of pore pressure based on the theoretical value curve of pore pressure, combined with previous experience and the actual drilling information in the upper part. The collapse pressure SFG obtained from the acoustic wave curve and the three-dimensional principal stress numerical solution curve is the red curve in the right column of Figure 7. In some strata, the calculated collapse pressure is less than the pore pressure because of the relatively high values of strength parameters such as friction angle and bond strength in the strata calculated by acoustic wave. In this way, the lower limit of the mud density window on the depth section will take the value of pore pressure. The upper limit of mud density window is the smaller of 3D_ minimum horizontal principal stress curve and 3D_ overlying pressure. This shows that the three-dimensional numerical solution of in-situ stress can automatically and accurately select the minimum principal stress component as the upper limit of mud window under different stress states. However, it is difficult to do this in single well geomechanics analysis. This is one of the advantages of using the numerical solution of 3D geostress field to calculate the mud density window. The changing trend of pore pressure curve in the right column of Figure 7 is that the uppermost Shawan Formation is at normal pressure, and the pressure coefficient rapidly increases to a high pressure above 1.8 after entering Anjihaihe Formation, then gradually decreases to about 1.5 in Ziniquanzi Formation and Donggou Formation, and then gradually increases to a high pressure of about 2.5 in Lianmuqin and Shengjinkou Formation. The pressure coefficient decreased in Hutubihe Formation, increased in Qingshuihe Formation, and decreased in Kalazha Formation, and its value remained between 2.2 and 2.4. As the pressure curve of overlying strata in the figure is obviously lower than the value of the actual drilling mud curve, it shows that the pressure of overlying strata of the rock in this depth section below 4,400 meters in this well is greatly influenced by local structure, which shows the necessity and importance of three-dimensional in-situ stress field analysis.