Method for predicting residual life of corroded casing of high-temperature and high-pressure well

Abstract

A method for predicting the residual life of a corroded casing of a high-temperature and high-pressure well mainly comprises the following steps: (1) predicting the inner average corrosion rate and the outer average corrosion rate of the casing by adopting the gray neural network algorithm; (2) establishing an finite element model for the corroded casing, and simulating the corrosion process of the casing by utilizing the element birth-death technology, so as to acquire the critical failure wall thickness of the casing when the casing loses efficacy; (3) establishing a residual life prediction model for the corroded casing, and computing the residual life of the casing subjected to uniform corrosion, local corrosion and pitting corrosion by utilizing the approximate analytical method; (4) establishing a relation equation for zero dimension residual intensity and zero dimension internal pressure and steam temperature by utilizing the regression analysis method. Aiming at the limitation of the theoretical study, laboratory test and field data on prediction of the service life of the casing, the method can effectively predict the residual life of the casing in shorter time, and the established residual intensity relation equation enables the engineering personnel to perform comprehensive evaluation on the service capability of the casing.

Description

technical field [0001] The invention relates to a method for predicting the remaining life of a corroded casing in a high-temperature, high-pressure well, which is applied to the replacement and maintenance of the corroded casing in a high-temperature, high-pressure well, and belongs to the technical field of oil and gas field control. Background technique [0002] Casing plays an extremely important role in the exploration and development of oil and gas wells. With the continuous exploitation and development of oil and gas fields, the resulting casing corrosion failure problem is becoming more and more serious. According to statistics, from 1997 to 1999, 61 wells in Zhongyuan Oilfield suffered casing failure due to corrosion, accounting for 16.8% of the number of wells with casing damage in the same period; from 1998 to 2000, 70 wells in four well areas of Tarim Oilfield were logged , 35 wells were found to have casing corrosion, accounting for 50% of the total well loggin...

AI Technical Summary

Problems solved by technology

[0003] The service casing in high-temperature and high-pressure wells has been in a complex and changeable environment for a long time. The formation water around the casing and the corrosive substances in the injected water will interact with the casing wall, which is very easy to corrode and form corrosion defects, which in turn cause casing failure. Partial thinning of the pipe wall reduces the effective strength of the casing, shortens the service life of the casing, and even makes the entire well scrapped

Due to the fact that there is no specific formula for the calculation of casing life in theory, and limited by the laboratory test conditions, it is impossible to conduct research on the corrosion life of casing running for a long time. In addition, the downhole service environment is complex and changeable. Tube life data are limited

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