Friction Calculation And Admittance Analysis Of Horizontal Well Casing

With the development of horizontal well technology, design and construction of the horizontal well casing string, an important field of oil-gas well engineering, concerned well completion and proper implementations of follow-up projects, such as production, stimulation and workover. For horizontal wells, due to large borehole curvature in curved section and long lateral segment, casing stress is very complex during the process of casing running, so it’s necessary to calculate and analyze the frictional resistance and the strength, which could provide scientific advice and necessary technical supports for horizontal drilling design (drilling equipment selection, borehole trajectory parameters, string design and string running design, etc) and construction safety (well trajectory control, string running and underground operations, etc)This paper analyzed and studied the calculation of frictional resistance and feasibility of casing running for horizontal wells. Major work is listed below:(1) Cubic spline interpolation method was used to fit the actual well trajectory. According to the fitted data, casing friction mechanical model was established, considering the effects of mud viscous resistance. Meanwhile, this paper analyzed the impact of dynamic loads that might occur during case running on axial loads and deduced the calculating model of dynamic loads. Then this paper evaluated the dynamic loads proportion of payloads and proposed measures of controlling and using the dynamic loads.(2) Considering the effect of curvature on casing running, this paper calculated the maximum curvatures that casing could pass through with different casing sizes and established the casing and the wellbore geometry compatible model. Based on elastic model, this paper calculated and analyzed the maximum length of single casing that can pass through the certain borehole curvature, which ensured the rigid casing to be run through the maximum curvature successfully.(3) Based on the mechanical condition of the casing running, this paper studied the internal force, the outer squeeze force and axial force. According to the fourth strength theory, this paper checked the strength of the completion strings and analyzed the safety of casing running.(4) Based on the above findings and VB6.0programming language, a software that can predict feasibility of casing running for horizontal wells was written and was applied in two horizontal wells in a block to analyze the feasibility of casing running. The application results showed that the error between calculating results and tests results on site lied in a reasonable range, which proved that this model was reliable and able to predict the frictional resistance and axial loads during casing running. This model provided theoretical basis for judging whether casing could be run successfully. Besides, combining with actual construction on site, this paper established the technical measures of casing running for this block.