THE DESIGN OF THE TRAJECTORY OF A SPATIALLY DEVIATED WELL

Abstract

Natural spatial deviation is due to the non-conformity of the type of a BHA and geotechnical drilling conditions at a certain interval, as well as mistakes in conducting geological exploration. The article presents the method which benefits the most from the natural deviation and the use of non-directional bottom hole assemblies. The main idea of this method lies in the fact that the design of the well trajectory is directed from the center of the target area to the wellhead. The article describes the main sections which constitute the trajectory of a spatially deviated well including the section of big diameter in the upper intervals. The input data necessary for designing the profile are given. The authors present the method of calculating the drilling lot using non-directional BHAs. The method consists of several cyclic repetitive operations and each subsequent interval of the wellbore is designed taking into account the change of the inclination and azimuthal angles in the previous interval. The authors conduct the survey of devices for drilling the borehole section which is made using a directional BHA. In rotor drilling, the technical devices and directional drilling technology are quite complex, therefore whipstocks with mud motors are used more often. As a result of calculating the trajectory of the well with different transition points between directional andnon-directional BHAs on the axis parallel to the azimuth direction, an array of transition points from two-axis to single-axis directional BHAs is formed. When drawing these points on the well plan, the ellipse of intermediate depths of BHA change is formed. This ellipse makes it possible to choose the optimal two-axis BHA using the necessary inclination angle values at the final stage of drilling a big diameter wellbore and using the final depth of this interval. On the basis of the this method the authors create software that allows automating the process of designing the well trajectory, taking into account the change of geology in the log, technical parameters of wells construction and technological parameters of drilling. This software was used while designing a well trajectory, referring to certain geological drilling conditions.