Abstract:

With the increase of infill and sidetrack wells, more and more sidetrack wells require more bypassing obstacles and become more difficult to be planned and drilled. The planning process of sidetrack wells for bypassing obstacles generally includes describing the configuration of obstacles, planning path of the sidetrack well for bypassing obstacles in the horizontal projection drawing and vertical plots and calculating the well path. Considering the shape of well trajectory in space and the change of anti-collision distance from adjacent wells along well bore, the obstacle of drilled well was assumed as the frustum of a curved-axis cone, and a model for describing the obstacle contour was provided. According to the geometric relationship among sidetrack point, target and obstacle area, the methods and optimizing criterion for planning the sidetrack well path for bypassing obstacles in the horizontal plot were presented by using single arc and double arc profiles. On the basis of the characteristics of sidetrack wells, a universal well-bore profile in the vertical plot and the corresponding design method were given. The coupling relationship of nodes in the horizontal projection drawing and vertical plots was analyzed, and the method for dividing well path into sections corresponding to the cylindrical helix model of well-bore trajectory was obtained. Thus, the obstacle area, plan and calculation of well path can be reasonably determined. The science and applicability of the methods was validated by examples.

Key words: sidetrack well for bypassing obstacles, planning method, well trajectory, mathematical model, directional drilling, well profile, optimization design

摘要：

随着加密井和侧钻井数量不断增加,侧钻绕障井越来越多,其设计和施工难度也越来越大。侧钻绕障井设计一般应包含:障碍物的形态描述;绕障井轨道的水平投影图设计;垂直剖面图设计;绕障井轨道计算。考虑井眼轨迹的空间形态和安全绕障距离沿井深变化等因素,将作为障碍物的已钻井抽象为空间曲圆台,给出了障碍物的描述模型。根据侧钻点、靶点和障碍域之间的相互关系,提出了在水平投影图上采用单圆弧绕障和双圆弧绕障的设计方法及优化设计准则。结合侧钻绕障井的特点,提出了垂直剖面图的通用井身剖面及其设计方法。通过分析水平投影图与垂直剖面图上轨道节点之间的耦合关系,得到了符合圆柱螺线模型的计算单元划分方法,从而可以合理地确定障碍域并进行轨道设计与计算。用实例验证了设计方法的科学性和适用性。

关键词: 侧钻绕障井, 设计方法, 井眼轨迹, 数学模型, 定向钻井, 井身剖面, 优化设计