The Optimization Design Of Casing Centralizer Distribution In Horizontal And Extended Reach Wells

The casing eccentricity is always a difficult problem to affect the cementing quality in horizontal and extended reach wells. To improve the cementing quality, centralizers are usually used to reduce casing eccentricity on site. And the installation of the centralizers are spacing, under the influence of the gravitational effect, the casing between two adjacent centralizers will engender bending deformation. In the position of the large deflection produces cement channeling influencing cementing quality. Therefore, it is particularly important to analysis the reasonable spacing of casing centralizers.This paper based on analyzing the related data, proposed some matters need attention when centralizers are selected and installed. These recommendations can provide certain reference for field operation. And the author analyzed the origin of the center degree calculation method in SY/T5334-1996, concluded the narrow limitation of the domestic casing center degree standard, introduced the ultimate eccentricity, established the model of casing center degree calculation under the condition of the ultimate eccentricity, analyzed the law of each factor impact on the casing center degree, and put forward the thought of using ultimate eccentricity to design the casing center degree. The thought is beneficial to improve the casing center degree and satisfy the cementing displacement efficiency, and lay a good foundation to improve the cementing quality. Also the author analyzed the weightlessness of casing pipes. The calculation formula of buoyant weight is obtained. This paper analyzed the advantages and disadvantages of a variety of centralizer spacing calculation model at home and abroad. The author used the vertical and horizontal bending beam theory to establish the casing deflection calculation model of the one dimensional, the two dimensional and the three dimensional. Through the analysis of the stress of the casing, we deduced the theoretical formula for calculating the maximum casing deformation. At the same time, we established the three moment equations, combined with the new design method of casing center degree, we have established a complete set of theoretical model to design the casing centralizer distribution in horizontal and extended reach wells. Finally, the author used visual basic programming language to compile the calculation software of the casing centralizer distribution. Also the author used the example to calculate, the results proved the rationality and accuracy of the theoretical model.