Study Of Mechanical Behavior Of Layered Water Injection String In Vertical Well

Layered water injection pipe string plays a significant role in oilfield water injection development.With the process of several packers separating layer in layered water injection,the possibility of string's damage increases because of the packers' restraint,operating conditions and complex loads.Thus,the stress and strain of the layered water injection string in the vertical well have been analyzed in this paper using the mechanical analysis method.The buckling differential equations of tubing string was established,using the tubing string mechanics.The contact force between tubing and casing was analyzed.Considering the axial force,temperature effect,ballooning effect and buckling effect,the axial deformation and strength of tubing string was calculated.A field test was conducted to study how buckling affect axial force.The tubing string mechanics and structure stability theory was applied to analyze buckling behavior of separate layer water injection string with two sides hinged support.The mechanics method of tubing string with more hinged support was proposed.Taking account of the temperature effect during the water injection,the heat conductivity equation of wellbore was obtained.Temperature change law of tubing string was analyzed during the water injection.Considering the pump pressure and Injection rate,the ballooning of tubing string and friction of fluid were analyzed.In addition,the method was applied to calculate the maximum strength and deformation of tubing string during the different pump pressure and injection rate.Based on the theoretical analysis,the safety evaluation method of separate layer water injection string and controlling method of pump pressure were proposed.