Force Analysis Of Drill-grinding Combined Tubing String And Research Of Running Ability In Horizontal Well

With the rapid development of unconventional oil and gas fields,the number of horizontal wells and horizontal section length are increasing,the long horizontal section of horizontal well can improve the production of oil and gas well.However,the structure of the wellbore with long horizontal section and high water than vertical leads to complicated force and large friction resistance during the running process of drill-grinding string,and influenced the drill-grinding string running ability.For drill-grinding string running difficulties,the oilfield adopted drill-grinding combined tubing string for drill-grinding operations.drill-grinding combined tubing string adopts the joining pattern of two-line weight tubing combinations.By changing the weight of the string in the vertical section and deviated well section of horizontal well improve the effective thrust of drill-grinding string,increases the drill-grinding string running ability.However,adopting the drill-grinding string of the joining pattern of two-line weight tubing combinations is no systemic study on the questions about the variation law of running load,the mechanism of running ability improvement,the reliable basis for the selection of the joining pattern of two-line weight tubing combinations and the passing ability of drill-grinding string.For the above problems,this paper carried out research on the joining pattern of two-line weight tubing combinations and the running ability.At first,according to drill-grinding operation technological process,for drill-grinding combined tubing string the characteristics of variable diameter location.The string buckling effect,internal and external fluid pressure,internal and external pressure,and wellbore trajectory are fully considered.The entire drill-grinding combined tubing string is separated into n-1element by using the micro-element method.The forces of the drill-grinding combined tubing string element in each well section are analyzed.In view of the string elements in vertical,stable,deviated and horizontal well sections of horizontal well in fluid environment,the running load calculation model of drill-grinding combined tubing string is established.Based on the actual parameters of YP10,CP13,AP18,AP24horizontal wells in the oilfield site,an example verification was performed,and the model was used to study the characteristics of the joining pattern of two-line weight tubing combinations and force analysis of tripping.Relevant results show that the calculated hook load force and frictional force are basically consistent with the field measured data.The average error of the hook load force is about 8.12%,and the average error of the friction force is about 8.825%.The error is within a reasonable range.The accuracy of the calculation model was studied.Taking 2 ⁷/₈'tubing combination 3 ¹/₂'tubing as the research object,it was verified that the two-line heavy tubing combination can increase the ability of the string running.Among them,when the deformation of the string is ignored,and the length of the string occupied by the 3 ¹/₂'tubing is the depth of the well trajectory at a well deflection angle of about 70.8°,the combination ratio of two-line weight tubing is optimal.The difference in friction coefficient?affects the different combination ratios of the two-line weight tubing.The larger the friction coefficient,the smaller the large line weight tubing accounts for the entire drill-grinding combined tubing string.At the same time,with the increase of the speed of drill-grinding combined tubing string,the running ability of drill-grinding combined tubing string is reduced.The content of the study provides theoretical guidance for horizontal well string construction.