Analysis Of Drag & Torque On Downhole Tubular String In Horizontal Well For Shale Gas In Mountainous Area

Horizontal well as the fundamental method of shale gas exploitation in mountainous area,has been applied widely.But horizontal extended-reach well also encounters many problems.Drag & torque problem of downhole tubular string is one of them.Horizontal extended-reach well is more complicated than conventional horizontal well in well trajectory,the constrain conditions of downhole tubular string,borehole clean and so on.When downhole drag is increased abnormally,bit can not get enough weight from ground,and mechanical load will show abnormal,even lead to downhole complexity and accident.First,this thesis illustrates the main factors affecting downhole tubular string drag& torque and its control methods.Second,the relative research work has been done in this thesis for calculating the side forces of downhole tubular string acted on horizontal curved borehole section.Third,using some data from the shale gas wells such as well Jiaoye 81-2HF in Fuling Shale Gas Field and well H3-2 in Changning Shale Gas Field,distribution of downhole tubular string drag & torque was calculated to give some results with the reference value.Finally,taking the self-lock of downhole tubular string as the objective function,this thesis gives the casing running limitation of horizontal extended-reach and the feasibility for casing running operations upward and downward when casing stopped at diameter shrinking segment of shale stratum,thus the program is developed.This thesis gives some new cognition about the effect of the length & gap of horizontal curved borehole on the side force and the quantitative analysis method of feasibility for casing running operations upward and downward.