Limits...
Burst strength of tubing and casing based on twin shear unified strength theory.

Lin Y, Deng K, Sun Y, Zeng D, Liu W, Kong X, Singh A - PLoS ONE (2014)

Bottom Line: Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design.Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models.The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), Chengdu, Sichuan, 610500, China.

ABSTRACT
The internal pressure strength of tubing and casing often cannot satisfy the design requirements in high pressure, high temperature and high H2S gas wells. Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design. The ISO 10400: 2007 provides the model which can calculate the burst strength of tubing and casing better than API 5C3 standard, but the calculation accuracy is not desirable because about 50 percent predictive values are remarkably higher than real burst values. So, for the sake of improving strength design of tubing and casing, this paper deduces the plastic limit pressure of tubing and casing under internal pressure by applying the twin shear unified strength theory. According to the research of the influence rule of yield-to-tensile strength ratio and mechanical properties on the burst strength of tubing and casing, the more precise calculation model of tubing-casing's burst strength has been established with material hardening and intermediate principal stress. Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models. The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.

Show MeSH
Relationship between the ratio of test data to calculations and the radius-thickness ratio (D/t).
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pone-0111426-g005: Relationship between the ratio of test data to calculations and the radius-thickness ratio (D/t).

Mentions: To validate the accuracy of the new model, the calculations of burst strength for the 16 kinds of frequently-used casing (7<D/t<26) have been presented in Table 1. In general, it can be observed from Table 1 that the calculations of model are PiR-API<PiR-New<PiR-ISO<PiR-Nadai. It can be seen from Figure 5 that PiR-API is considerably less than the test data; PiR-Nadai is considerably larger than the test data; PiR-ISO is close to the test data, but its calculations is almost larger than the test data, which makes against the casing design and improvement of upper limit of safety coefficient. However, PiR-New is quiet closer to the test data and its calculations are only slightly less than the test data (to meet the requirement of engineering design, the calculations must be less than real values, but not 10 percent less than real values), which is beneficial to casing design of deep and ultra-deep wells and improvement of upper limit of safety coefficient on the basis of material safety which was guaranteed. So the new model is more accurate and reasonable than other models.


Burst strength of tubing and casing based on twin shear unified strength theory.

Lin Y, Deng K, Sun Y, Zeng D, Liu W, Kong X, Singh A - PLoS ONE (2014)

Relationship between the ratio of test data to calculations and the radius-thickness ratio (D/t).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232241&req=5

pone-0111426-g005: Relationship between the ratio of test data to calculations and the radius-thickness ratio (D/t).
Mentions: To validate the accuracy of the new model, the calculations of burst strength for the 16 kinds of frequently-used casing (7<D/t<26) have been presented in Table 1. In general, it can be observed from Table 1 that the calculations of model are PiR-API<PiR-New<PiR-ISO<PiR-Nadai. It can be seen from Figure 5 that PiR-API is considerably less than the test data; PiR-Nadai is considerably larger than the test data; PiR-ISO is close to the test data, but its calculations is almost larger than the test data, which makes against the casing design and improvement of upper limit of safety coefficient. However, PiR-New is quiet closer to the test data and its calculations are only slightly less than the test data (to meet the requirement of engineering design, the calculations must be less than real values, but not 10 percent less than real values), which is beneficial to casing design of deep and ultra-deep wells and improvement of upper limit of safety coefficient on the basis of material safety which was guaranteed. So the new model is more accurate and reasonable than other models.

Bottom Line: Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design.Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models.The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), Chengdu, Sichuan, 610500, China.

ABSTRACT
The internal pressure strength of tubing and casing often cannot satisfy the design requirements in high pressure, high temperature and high H2S gas wells. Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design. The ISO 10400: 2007 provides the model which can calculate the burst strength of tubing and casing better than API 5C3 standard, but the calculation accuracy is not desirable because about 50 percent predictive values are remarkably higher than real burst values. So, for the sake of improving strength design of tubing and casing, this paper deduces the plastic limit pressure of tubing and casing under internal pressure by applying the twin shear unified strength theory. According to the research of the influence rule of yield-to-tensile strength ratio and mechanical properties on the burst strength of tubing and casing, the more precise calculation model of tubing-casing's burst strength has been established with material hardening and intermediate principal stress. Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models. The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.

Show MeSH