Abstract: In this paper,a new model for calculating formation forces is developed on the basis of the principle of rock-bit formation interaction and the analysis of the forces on a bit.The emphasis is put on well trajectory change and formation anisotropy in this model.It overcomes the shortcomings of previous models in which formation forces are calculated only on the condition of unchanged well trajectory to make the model more useful.The distribution of formation forces and their influence factors are discussed in detail.On the basis of the actual drilling data from the southern region of Daqing oilfield we have obtained the formation forces and the ratio of formation force to bit weight.The average ratio is 0.74%.

摘要： 根据钻头与地层相互作用理论,结合钻头的力学分析,建立了地层力计算的新模型.模型重点考虑了井眼轨迹变化和地层各向异性的影响,克服了以往只能由稳斜稳方位(或稳斜)条件确定地层力的缺点,它适用于井眼轨迹任意变化的状态.模型具有广泛的使用价值.文中还讨论了地层力的影响因素和分布特征.并结合大庆油田南Ⅱ区的实钻井史资料,得出了该地区的地层力数值和地层力与钻压的平均比值为0.74%.

关键词: 地层力, 各向异性, 井眼轨迹, 钴压