Research On Key Cementing Technology Of Inclined Horizontal Well

Inclined-straight horizontal wells start to increase the inclination after drilling into a certain depth of the formation at a certain inclination angle using a special inclined straight shaft drilling rig.Aiming at the characteristics of thin thickness and shallow burial depth of shallow heavy oil target layer in Xinjiang Oilfield,the wellbore structure was optimized,and the wellbore trajectory profile was designed.Different from conventional directional wells,the casing string lies on the lower downhole wall when the inclined straight section is under the casing,and it is subjected to a large frictional resistance.At the later stage of the casing,only the weight of the casing itself is insufficient to make the casing fall into the bottom of the well.In response to this problem,the following aspects of research have been carried out:(1)Design of borehole structure and borehole trajectoryAccording to the well quality and target front distance requirements of a block in Xinjiang Oilfield,the stratus of the heavy oil block in Xinjiang Oilfield is dominated by medium-fine sandstone,fine sandstone,siltstone,gravel-bearing medium-fine sandstone and softer strata.A reasonable wellbore track and well structure will be designed.(2)Analysis of the frictional resistance model of casing string in shallow inclinedstraight horizontal wellAccording to the fitted wellbore trajectory data,the frictional and axial forces of the casing are calculated by the two-dimensional soft rod model and the factors affecting the casing friction are analyzed.Relatively speaking,in the casing process,the dynamic load has a significant influence on the viscous force and pressure difference of the drilling fluid.(3)Friction coefficient calculation of down casingStarting from the relative radius of the casing and the wellbore,combined with the theory of friction and contact area,the true contact area is analyzed by the Hertz theory in contact mechanics,and the coefficient of friction of the casing is calculated.According to the calculation of different calipers,the friction coefficient of the same casing under different boring diameters is obtained.The frictional resistance of the casing is inversely proportional to the annulus clearance under certain conditions.(4)Study on the ability of casing string passing in curved sectionBy analyzing the influence of axial force and centralizer on the maximum curvature of casing in curved section,a calculation model of maximum curvature of casing is established.(5)Compilation and application of calculation software for casing string loadUsing MATLAB mathematic tool to calculate,the program of casing penetrability analysis for shallow inclined vertical wells is compiled.The calculation results are compared with those of adjacent shallow inclined-straight horizontal wells in the study block,and the results are in good agreement with the actual situation.