基于空间球对称模型的井底岩石可钻性研究

针对井底复杂应力环境下的岩石可钻性问题，开展了岩石可钻性和岩石单轴抗压强度实验和理论研究，研究 中采用弹性力学理论和Drucker-Prager 强度准则，建立了球坐标系下的井底岩石可钻性模型，并以川西地区某井须家 河组致密砂岩实验数据和测井资料为基础，进行了算例分析。结果表明，井底岩石可钻性随着液柱压力的增大而增 加；井深一定时，沿井底表面径向方向，随着距离的增加，岩石可钻性增大。该模型计算结果，能够较好地反映井底岩 石可钻性级值的变化规律，有助于钻具优化设计。

A Bottomhole Drillability Model in Spherical Symmetric Coordinates

Aiming at bottomhole drillability in complex stress conditions，experimental and theoretical studies were carried out in this paper，including drillability and uniaxial compressive strength tests. A bottomhole drillability model was established in spherical symmetric coordinates，based on the elasticity theory and Drucker-Prager strength criterion. A case was done according to the drillability test data and well logging data from sandstone reservoir in Xujiahe group. The results show that bottomhole drillability increases with the increase of fluid column pressure in wellbore. Bottomhole drillability also increases along the radial direction. This drillability model can well reflect the law of bottomhole drillability and contributes to BHA optimization design.