Theoretical and experimental analyses of casing collapsing strength under non-uniform loading
来源期刊：中南大学学报(英文版)2014年第9期
论文作者：LIN Yuan-hua(林元华) DENG Kuan-hai(邓宽海) ZENG De-zhi(曾德智) ZHU Hong-jun(朱红钧) ZHU Da-jiang(朱达江) QI Xing(戚兴) HUANG Yun(黄韵)
文章页码：3470 - 3478
Key words：non-uniform loading; mechanical model; collapse testing; collapse strength
Abstract: Failure data from oilfield showed that casings which were designed according to API standards were deformed and collapsed in salt formations. The main reason for decrease in strength may be caused by non-uniform loading (NUL) that was not considered in traditional casing collapsing strength design or that the designing method should be improved and developed. Obviously, the calculation of casing collapse strength is one of the key factors in casing design. However, the effect of NUL on casing collapse strength was generally neglected in the present computational methods. Therefore, a mechanical model which can calculate casing collapse strength under NUL was established based on the curved beam theory of the elasticity and was solved using displacement method. Simultaneously, three anti-collapse experiments were performed on C110 casing under NUL, and the strain and deformation laws of three casings in the process of collapse were obtained by the electrical method. Yield limit of every casing was obtained by analyzing those data. Experimental results are consistent with the results of calculation of new model. It indicates that the model can be used to calculate yield limit loading of casings under NUL.
LIN Yuan-hua(林元华)1,2, DENG Kuan-hai(邓宽海)1, ZENG De-zhi(曾德智)1, ZHU Hong-jun(朱红钧)3, ZHU Da-jiang(朱达江)1, QI Xing(戚兴)3, HUANG Yun(黄韵)2
(1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), Chengdu 610500, China;
2. School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China;
3. National Petroleum Corporation Key Lab for Tubular Goods Engineering (Southwest Petroleum University), Chengdu 610500, China)
Abstract:Failure data from oilfield showed that casings which were designed according to API standards were deformed and collapsed in salt formations. The main reason for decrease in strength may be caused by non-uniform loading (NUL) that was not considered in traditional casing collapsing strength design or that the designing method should be improved and developed. Obviously, the calculation of casing collapse strength is one of the key factors in casing design. However, the effect of NUL on casing collapse strength was generally neglected in the present computational methods. Therefore, a mechanical model which can calculate casing collapse strength under NUL was established based on the curved beam theory of the elasticity and was solved using displacement method. Simultaneously, three anti-collapse experiments were performed on C110 casing under NUL, and the strain and deformation laws of three casings in the process of collapse were obtained by the electrical method. Yield limit of every casing was obtained by analyzing those data. Experimental results are consistent with the results of calculation of new model. It indicates that the model can be used to calculate yield limit loading of casings under NUL.
Key words:non-uniform loading; mechanical model; collapse testing; collapse strength
