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Stress sheath demage predicting method

A prediction method and stress technology, applied in the direction of measuring force, measuring device, using stable tension/pressure to test the strength of materials, etc., can solve problems such as inability to predict casing damage

Active Publication Date: 2006-12-20
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

[0098] Embodiment 1: Casing anti-internal pressure strength:

[0099] 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, and the elastic-plastic strength of the casing P p ′ is 66MPa. When the external load (internal pressure) reaches this value, it begins to enter the elastic-plastic stage, and its change law is no longer a linear relationship, and its strain change range is only 0.1 mm to 0.2 mm. Instrumental monitoring of its changes is very difficult. The strength of casing against internal pressure increases more and more slowly, but the value is still relatively large, and the ability of casing to resist internal pressure is still relatively large, which is not the main type of casing damage in oilfields. Series 2, 3, and 4 are the situations when the internal pressure is 10, 20, and 30 MPa. It can be seen that the internal pressure resis...

Embodiment 2

[0100] Embodiment 2: Uniform external pressure resistance strength:

[0101] Figure 5 The middle 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, and the elastic-plastic strength of the casing P p ' is 66MPa. When the external load (external pressure) reaches this value, it begins to enter the elastic-plastic stage, and its change law is no longer a linear relationship. The strain range varies from 0.2 mm to 2.5 mm. Monitor the radial strain u of the casing r , the casing stress load P can be inverted by the formula (3) of the present invention p . The strength of casing against uniform external pressure increases more and more slowly, but the value is still relatively large. The ability of casing to resist external pressure is still relatively large, and the main types of casing damage in oilfields are not like this. Series 2, 3, and 4 are the situati...

Embodiment 3

[0102] Embodiment 3: Anti-inhomogeneous external pressure strength:

[0103] Image 6 Series 1 is the stress-strain relationship of the casing against non-uniform external pressure when the pressure difference between the inside and outside of the casing is 0. The elastic-plastic strength of the casing is 5.6MPa, which is less than 10% of the uniform value. When a value begins to enter the elastic-plastic stage, its change law is no longer a linear relationship, the load resistance strength drops rapidly, and its strain range varies from 0.3 mm to 15 mm. The radial strain of the casing is monitored with a casing caliper measuring instrument u r , the casing stress load P can be inverted by the formula (3) of the present invention p . This type of casing damage is the most harmful. Series 2, 3, and 4 are the situations when the internal pressure is 10, 20, and 30MPa, and the ability of the casing to resist non-uniform external pressure decreases with the increase of interna...

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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 of oil and water wells in an oil field, and belongs to a method for predicting casing damage due to stress. Background technique: [0002] Casing damage refers to the abnormal damage or deformation that affects the production of oilfield production pipelines. The prediction of oilfield oil and water well casing damage 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 acoustic caliper instruments, magnetic caliper instruments and mechanical caliper instruments, etc., to monitor the change in radial strain of the casing. If the radial strain is uniform along the circumferential direction, the same as Compared with the original casing, the enlarged borehole diameter can judge the type of external load as internal pressure, and the t...

Claims

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Application Information

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