Research on Minimum Length Calculation of Skid-Mounted Small-Diameter Pipe Weight Bar

The drainage gas recovery operation with small-diameter continuous pipes is applicable to the one in natural gas well with low pressure, low production and low water content. Its advantages exhibit as the following: 1) high efficiency on continuous running of pipe string under pressure; 2) production while operation; 3) correct monitoring the position of ejection head; and 4) précised control of ejection quantity. Due to the small diameter, thin wall thickness and relative low rigidity of pipe string, it is easy to cause bending and deformation during down-hole process and affect the capability of small diameter pipe operation. Aiming at shutting and opening of the well, this thesis analyzes the force of the small-diameter pipe during down process, establishes the corresponding digital model and proposes the calculating method required to run the small-diameter pipes under different status. Taking G25-5 well as example, the appropriate minimum length of weight bar under different working status is given to verify the validness of the method to determine the minimum length of weight bar. Keywords-Skid-Mounted Small-Diameter Pipe; Drainage Gas Recovery & Weight Bar