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Wang W.,Jilin University | Peng J.,Jilin University | Wang H.,China National Petroleum Corporation | Chen C.,Jilin University | And 2 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2014

In the process of drilling in gas hydrate formation, the drilling disturbance may have a profound influence on the wave velocity of the bottom and surrounding formation of the hole. So it is difficult to obtain accurate information of the gas hydrate formation by core drilling analysis and logging. Using finite element analysis software ANSYS/LS-DYNA, the finite element model of the pressure core sampler (PCS) bit drilling in the gas hydrate formation was built, and the dynamic process of PCS bit drilling in the gas hydrate formation was simulated. The disturbance morphology at different time was obtained. The influence relationship of bit weight and rotary speed on the disturbance of gas hydrate formation also was acquired at the same time. The results show that, firstly, when rotary speed is constant, the disturbance degree of undrilled sub bottom hole near the cutting shoes and underground layer around the well near the PCS bit increases with the increase of the bit weight. Secondly, when bit weight and rotary speed are both constant, the shorter distance between the bottom formation of the hole and the cutting shoes in the drilling direction, the bigger disturbance degree will be obtained, and contrarily it would be smaller. The disturbance degree of bottom formation of the hole is relatively big when the distance to the cutting shoes is shorter than 0.09 m, while it is relatively small out of this distance. Meanwhile, the shorter distance between the surrounding formation of the hole and the PCS bit in the radial direction, the bigger disturbance degree will occur, and contrarily it could be smaller. The disturbance degree of surrounding formation of the hole is relatively big when the distance to the cutting shoes is shorter than 0.055 m, while it is relatively small out of this distance. The results can make a good reference for the PCS coring analysis and hydrate logging. Source

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