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Stress sheath demage predicting method

A prediction method and stress technology, applied in the direction of measuring force, measuring device, and testing the strength of materials by applying stable tension/pressure, which can solve problems such as inability to predict casing damage

Active Publication Date: 2005-03-23
DAQING OILFIELD CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] In order to overcome the problem that existing logging instruments can only monitor casing strain and formation stress, but cannot predict casing damage, the present invention provides a stress-induced casing damage prediction method, which can predict the possibility of casing damage , to take remedial measures on the casing before the casing damage occurs, which can slow down or avoid the casing damage and greatly reduce the repair cost

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0082] Example 1: Casing anti-internal pressure strength:

[0083] Figure 4 The middle series 1 is the stress-strain relationship of the casing against internal pressure when the pressure difference between the inside and outside of the casing is 0, the casing elastic-plastic strength P p ′ Is 66MPa. When the external load (internal pressure) reaches this value, it starts to enter the elastoplastic stage. The change rule is no longer a linear relationship, and the strain change range is only 0.1 mm to 0.2 mm. The existing casing damage detection It is very difficult for the instrument to monitor its changes. The internal pressure resistance of casing increases more and more slowly, but the value is still relatively large, and the internal pressure resistance of casing is still relatively large. The main type of casing damage in oilfields is not this. Series 2, 3, and 4 are the situations when the internal pressure is 10, 20, and 30MPa. It can be seen that the casing's internal p...

Embodiment 2

[0084] Example 2: Resistance to uniform external pressure:

[0085] Figure 5 Medium series 1 is the stress-strain relationship of the casing against uniform external pressure when the pressure difference between the inside and outside of the casing is 0, the casing elastic-plastic strength P p ′ Is 66MPa. When the external load (external pressure) reaches this value, it starts to enter the elasto-plastic stage. The change rule is no longer a linear relationship. The strain change range is from 0.2 mm to 2.5 mm. Use the casing diameter measuring instrument Monitoring the radial strain u of the casing r , Through the formula (3) of the present invention, the casing stress load P can be inverted p . The strength of casing against uniform external pressure increases more and more slowly, but the value is still relatively large, and the capacity of casing to resist external pressure is relatively large, and the main type of casing damage in oilfields is not this. Series 2, 3, and 4 a...

Embodiment 3

[0086] Example 3: Anti-uniform external pressure strength:

[0087] Figure 6 Series 1 is the non-uniform external pressure stress-strain relationship of the casing when the pressure difference between the inside and outside of the casing is 0. The elastoplastic strength of the casing is 5.6 MPa, which is less than 10% of the uniform pressure. When the external load (non-uniform external pressure) reaches this At a value, it enters the elasto-plastic stage, its change rule is no longer a linear relationship, the load strength drops rapidly, and its strain varies from 0.3 mm to 15 mm. The casing diameter measuring instrument is used to monitor the radial strain of the casing. u r , Through the formula (3) of the present invention, the casing stress load P can be inverted p . This type of sleeve damage is the most harmful. Series 2, 3, and 4 are the situations when the internal pressure is 10, 20, and 30MPa. As the internal pressure increases, the casing's ability to resist non-unif...

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Abstract

The invention discloses a forecasting method for stress damage. Its character lies in: at first, the radius strain of and ground stress are supervised; secondly, takes no account of affection of sleeve pipe axis stress, the sleeve pipe is considered as ring stress problem in condition of plane, deduces out the radius strain formula generated by the ring plastic deformation and the sleeve pipe plastics intensity formula, works out the stress carrier and correspondent limit intensity according to the two formulas. Finally, through the comparison of sleeve stress carrier and sleeve limit intensity, it judges the probability of damage.

Description

Technical field: [0001] The invention relates to a method for predicting casing damage in oil and water wells in oil fields, and belongs to a stress-induced casing damage prediction method. Background technique: [0002] Casing damage refers to the abnormal damage or deformation that affects the production of oilfield production pipelines. The prediction of casing damage in oil and water wells in oilfields has not found relevant technical reports and applications in major oilfields at home and abroad; monitoring of casing stress load changes The method is to use existing casing caliper measuring instruments, namely sonic caliper instruments, magnetic caliper instruments and mechanical caliper instruments, to monitor the radial strain change of the casing. If the radial strain is uniform along the circumferential direction, Comparing the original casing, the diameter expansion can judge the external load type as internal pressure, and the diameter reduction can judge the external ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01L1/00G01N3/08
Inventor 付泽民
Owner DAQING OILFIELD CO LTD
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