Research On Stress Detection Techniques Of Casing Damage Magnetic Survey Of Oil-Water Well

In the course of the use of the oil-water well casings,besides the condition of the resistance to corrosion,the casings are influenced by various complex factors such as the geological factors,engineering technology factors and development mode factors,so it is difficult for them to achieve the natural life of the design.According to the statistics,now the casing damage wells account for about 20% of the active wells,and the casing damage seriously affects the crude oil production of various oil fields,including Daqing Oilfield,so it is currently the urgent difficult problem which is faced by the oil and gas production in the oil industry to solve.Corrosive causes of casing damage are easy to determine,and also easy to measure.In the middle and late stage of development and exploitation of the oil field,the cause of casing damage is very complicated,and however,the stress damage is the main cause of casing damage.The study of effective detection of the casing stress and the measures to develop the predictive detection of casings and to predict the service life of the casings,and the effective comprehensive treatment scheme to be formulated and implemented based on the study are the urgent and important matters of the casing damage prevention and control work,and they have important practical significance for the oilfield productivity construction and sustainable development.This paper deals with the situation facing the sustainable development of Daqing Oilfield40 million tons of oil and gas equivalent,and aims at the present situation of casing damage of Daqing Oilfield,focuses on carrying out the development and performance test of the finite element simulation and the stress sensor of the casing stress,and implementing the development and application of the stress logging instrument,improving the matching technology of comprehensive detection of casing stress for the inner and outer sleeves and perfecting the stress detection method of magnetic survey for detecting the casing stress and the interpretive method of comprehensive detection for the casing damage.The main contents of the study include:1.The casing damage emerges as a result of the bearing stress overload.The study attempts to establish the stress model of stretching,shearing,bending and ring crush of the oil-water well casings in order to use the finite element software ANSYS to simulate the stress distribution of the oil-water well casing.The result shows that we can use the axial andcircumferential strain of the casing to estimate the casing safety state,and reveal the casing damage cause of the non-uniform load.2.In the basic study field of the casing stress detection,the paper studies the effect of the stress on the magnetic property of ferromagnetic materials and the magnetic stress mechanism through the magnetic domain theory,and establishes the stress detection method of a non-contact and nondestructive magnetic survey so that the study lays the theoretical foundation of the magnetic stress sensor.Through the application of the inverse magnetostrictive theory,the magnetic stress sensor has been designed and made,and the effective detection of the stress signals has been achieved.By using the circuit theory,the effective examination and discrimination of weak signals and shielding of the stray interference signals have been realized,and the accurate collection of the weak effective signals of the stress has been achieved.Through the experimental study of the sensor property,the measurement data can determine the nature of the stress and the conclusion of the stress quantization,and the data are consistent with the theoretical deduction conclusion.The study shows that the sensor can effectively distinguish the nature of the stress,and the magnetic signals which are detected and one-dimensional stress values show good linear relationship,and the stress values are close to the actual values,so this provides a basis for the norms of stress sensors of the quantitative calibration and the stress logging instruments,and provides a powerful detection method for the quantitative evaluation of casing damage.3.Through application of the control technique of the single chip microcomputer,the positioning technique of the optical fiber gyroscope and the stress sensor of six bearing magnetic survey to carry out the azimuth well logging,the matching superior management software has been developed,and the stress logging instrument of magnetic survey of the complete casing damage has been made and produced.The calibration of the magnetic stress logging instrument ensures the reliability of the field application of logging instruments.The result of application of the logging instrument shows that,when the instrument tests,the probe of the sensor does not require full contact with the inner wall of the casing;the stress bearing detection of the online casing damage is realized,and the “force-circle vector” imaging logging is proposed,as a result,the instrument has little dependence on the casing curvature,but it has the advantages of higher measurement accuracy.By using the logging instrument,the stress state of the casing can be quantitatively evaluated,and the determination method of the casing damage degree is put forward,so an effective testing method and a powerful data support are provided for preventing the casing damage.