Torque-drag And Extend Reaching Analysis In Horizontal Gas Drilling

Horizontal gas drilling is a new kind of drilling technology which can accelerate the drilling speed and protect the oil and gas reservoir perfectly.Although it is developed in recently years,attracts the attentions both at home and abroad.The technological advantage is obvious in accelerating the drilling speed,improving the oil and gas production a well and maintaining the stable time of production.It offers a new way to reduce the dirlling cost and improve the comprehensive economic efficiency of drilling.Although many advantages exist,there are two obstacles need to overcome before making this technology popularize.One is how to keep working efficiency from water when drilling;the other is improving the extended reaching length.Many works which focus on the latter are made in this paper.Combining with the theoretical research and experimental study,the dynamic characteristic and bending shape of drillstring are studied and the torque and drag is also studied.Some meaningful results are got based on these researches they are will make great influence to the development of horizontal gas drilling and offer the suggesting to the field practice This paper mainly carried out the following research work:(1)Domestic and international literature review.Gas drilling horizontal wells operating conditions,special equipment and operating system are in-depth analyzed,and the research progress,achievements and existing problems of domestic and international horizontal gas drilling are summarized.Besides,the existing domestic and international research results of the horizontal well friction and extended reach drilling the results of are investigated.(2)Establishment of horizontal gas drilling drillstring torque and drag model.Using Hamilton principle to establish gas drilling horizontal wells drill string dynamics model.To improve the accuracy of the model,the straight beam and bending beam unit are selected to deal with vertical section and horizontal section of the well respectively,and the main factors of gas drilling drill string damping are studied.Another,the features of hole enlargement,friction,well types and the contact behaviors between the drillsting and hole well are also considered in this model.Furthermore,four mathematical models of different contact conditions "collision,continuous contact,contact with sinusoidal buckling and helical buckling" are established by determining contacting state between the drill string and the borehole wall.(3)Experimental study of horizontal gas drilling friction coefficient.The influences of cuttings particle size,lithology,rock cuttings bed coating and cuttings bed thickness on and friction coefficient and their internal influence mechanism are analyzed through the simulation coefficient friction test platform between the drilling and borehole wall in horizontal section("drill string-naked rock borehole wall ","drill string-casing borehole wall”).(4)The bench testing of friction and buckling of drill string in horizontal gas drilling well.The proportional relationship between drillstring,borehole,experimental parameters and field parameters are studied based on the similarity theory;and the proportion of experimental bench of horizontal gas drilling which considering the effect of curved well segments is builded.In order to guarantee the precision of the experimental,the drillstring has been made a specific surface treatment to keep the friction in test approximately equal to the actual value.The effect of various drilling parameters(WOB,RPM)on the drillstring deformation and friction are researched under the situation of static loading(WOB)and dynamic loading(WOB,RPM);the precision of experiment is verified through the comparison of experiment value and theoretical calculating value.(5)The effect factors research of torque and drag in horizontal gas drilling.The phenomenon of Continuous slightly deflection in horizontal well is founded combining the correlational research and measured borehole trajectory data;and the law of deflection is obtained through the analysis of one case well measured trajectory.Take the CA2 well as an example,the effect of commonly used well type structure,drilling parameters,borehole diameter enlargement rate and friction coefficient on the torque and drag is analyzed.The main effect factor is found and the research direction of drillstring extension capacity in horizontal well is determined through the analysis of research results.(6)The research of drillstring extension capacity in horizontal well.Due to the situation of drillstring cannot lubricated by gas medium,the active antifriction tool is propose for the horizontal gas drilling;the tool can reduce the friction drag.The effectiveness of the passive tool is verified through the lab experiment.The objective optimization function of the well track design in horizontal gas drilling is established which take the minimum friction as the target.Sequential unconstrained minimization technique is adopted to improve the optimal solution and the drag is reduced through the trajectory optimization.The limitation factors of drillstring extension capacity in horizontal well are analyzed,and the prediction method of drillstring extension capacity which considering the effect of buckling of drill string is proposed.Then,the longest extended length of case wells is predicated.In this paper,the torque and drag is horizontal gas drilling is systematic researched through laboratory experiment and theoretical analysis.The main factors effect torque and drag is obtained,the affectivity method to reduce in horizontal gas drilling is determined and the prediction method of drillstring extension capacity is proposed.The research work is of great significance to promote the development and popularization of the technology of horizontal gas drilling.