关键词: 钻井理论, 定向钻井, 井眼轨迹, 数学模型, 计算方法

Abstract:

As a primary step of effectively controlling borehole trajectory, the design of borehole deviation control scheme has been widely applied in the process of directional drilling. Based on the spatial arc trajectory model, an interactive design method was proposed for the borehole deviation control scheme in this study, so as to solve the multi-valuedness problem of certain parameters, reveal the applicable conditions of special direction-turn modes, and describe the range of initial tool face angle for deviation gain or drop. The research results show that this interactive design method has optimal design and result check functions, and is easy to use onsite; the multi-valuedness problem of certain parameters, such as initial tool face angle, cannot be judged simply by deviation increment, but depends on the deviation rate at the terminal of direction turn; the steady-inclined and full direction turns should be limited within a certain well interval, which is can be characterized by allowable bending angle; the allowable bending angle of steady-inclined and full direction turns is unable to exceed 180° nor 90° respectively. The interval of steady-inclined direction turn is composed of two parts, i.e., deviation gain and drop with the midpoint of interval as the demarcation. The deviation gain or drop tendency of direction turn can be discriminated by initial tool face angle, while the demarcation line or area for initial tool face angle depends on the deviation angle at the starting point. The scientific and applicable research results have been validated by application examples.

Key words: drilling theory, directional drilling, wellbore trajectory, mathematical model, calculation method