A method for predicting oil and water well casing damage based on mudstone creep model

Abstract

The invention discloses a method for predicting oil-water well casing damage based on a mudstone creep model. The method is specifically as follows: firstly, based on the material balance method, the water content is calculated, and then the mudstone creep tests under different water contents are used to obtain different Stress and creep curves of mudstone strain changing with time under different water contents, substituting into the creep equation to calculate the creep model parameter E 1 ,E 2 ,E 3 , η 1 , η 2 , η 3 , a, Substituting the obtained parameters into the new mudstone creep equation, making it an explicit equation, and then numerically simulating the stress on the casing according to the calculated water content and the new mudstone creep equation, and obtaining the wellbore mudstone and The stress distribution of the casing, and finally, the obtained stress is substituted into the Mohr-Coulomb strength criterion including pore pressure, so as to judge whether the casing is damaged. Since the present invention considers the influence of the change of water content on the physical properties and rheological properties of mudstone, it has better applicability and accuracy.

Description

technical field [0001] The invention belongs to the field of oil and gas field development, and in particular relates to a method for predicting oil and water well casing damage based on a mudstone creep model. Background technique [0002] The lithology of most oil and gas reservoirs is sandstone and mudstone, and this type of surrounding rock has a creep reaction when exposed to water. In this process, the uneven change of the formation will cause the casing to be subjected to shear stress exceeding the maximum shear strength of the casing, resulting in damage to the casing. Especially in the process of oil well water injection development, since the injected water enters the soft rock formation along the perforation and rock formation fissures, the creep rate of the rock formation will be accelerated, the stress in the rock formation around the casing will be redistributed, and the displacement will change accordingly. , which will cause the bushing to be broken. [000...

AI Technical Summary

Problems solved by technology

However, they also have their own defects. Some models cannot simulate certain stages in the mudstone creep process, and some models have too complex constitutive structures, which make the model poorly adaptable, and cannot describe the impact of changes in water content on the physical properties of mudstone and its rheological properties. , thus affecting the analysis results of casing damage

Although the finite element model analysis method can intuitively reflect the change of the casing shear stress and provide a certain direction for the establishment of the rock creep model, there are still problems such as simplified calculation conditions, large amount of calculation, poor model convergence, and inaccurate structure. Disadvantages, it is not easy to be used alone to analyze and predict oil well casing damage

Therefore, existing oil well casing damage prediction methods are deficient to a certain extent, and are not suitable for large-scale application in field practice.

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