A method for 3D casing-centralizing design in Chuanyu oil and gas field
The centralizing degree of the casing has a big impact on the cementing quality.A reasonable casing-centralizing design will greatly improve the distribution of casing annular flow field,enhance the efficiency of annular displacement,ensure the quality of cement sheath,and lay a foundation for subsequent drilling and reservoir transformation.By analyzing the limitations of existing mainstream models for calculat-ing the centralizing degree of casing strings,it is proposed that due to the fact that the gravity and axial load acting on the casing string in a 3D wellbore are not located in a single plane,non planar bending deforma-tion will occur,and lateral force and radial displacement will be affected by changes in wellbore trajectory and buoyancy.Based on the 3D shape of the real wellbore trajectory,considering the influence of axial ten-sion on the deflection and buoyancy effects of the main and auxiliary normal planes,a 3D mathematical model of the single span beam casing-centralizing was established,and a simulation analysis and calcula-tion module was developed.By comparing with the centralizing degree of the imaging logging data,the re-sults indicate ①The calculation error of the single-span beam model is less than 7.6%;②Optimizations such as increasing the outer diameter of stabilizer in vertical well section and displacing with water to achieve floating effect on top of liner which reduced the radial offset of the casing string,reasonably shorten-ing the spacing between the rigid stabilizers in the upper vertical well section can improve the overall cen-tralizing degree up to 70%and the quality of cement sheath.This model can provide a good guidance for casing-centralizing design and annulus sealing quality of complex wellbores in Chuanyu oil and gas field.
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