Working String Axial Force in L-Shaped Oil Well

The bottom section of a L-shaped well warps upward, so it is a different type against normal horizontal well and should be designed carefully. With regard to the peculiar geometry of borehole, in this paper, the working string axial force is calculated and the feasibility of string running in and out the hole is discussed. String buckling and bottom sticking are considered. This papers suggested that the tip-tilted section makes string tripping in more difficult, while makes tripping out easier; during tripping out, the ratio between the increase of hook load and sticking force is a certain value; string buckling begins at the kick of point firstly and at the target secondly during tripping in; the friction caused by buckling in the L-shaped well is more obvious than in normal horizontal well; the smaller the string size is, the shorter the largest extending length will be. (paper)