The Casing Condition Logging And The Study Of The Method To Detect The Casing Stress

In order to meet the need of casing monitoring, inspection and damage prediction innational oil fields and enhance the development of production well logging technology, Thepaper developed high temperature rating and high pressure rating telemetry engineeringcombination logging tool with high data transmitting rate and took the leading study of themethod to inspect casing stress with the metal magnetic memory phenomenon in casing damageprediction at home and abroad.The conventional subs in telemetry engineering combination logging tool are ccl andtelemetry sub;the functional subs are azimuth logging tool, acoustic caliper and ultrasonicimaging televiewer. The telemetry sub is the core of organization and management of the system,which provides necessary support of software and hardware for data acquisition, processing andtransmission;the ultrasonic imaging televiewer visually presents the condition of interwall ofcasing and the borehole wall;the acoustic caliper quickly and quantitatively detects the status ofinterwall of casing and borehole wall;the azimuth logging tool provides the casing damagelocation demanded by ultrasonic imaging televiewer and acoustic caliper.The technologies such as pre-code, relative code, QAM modulation, match-balancedamplifying receiving and synchronous demodulation, etc. are studied and applied, then the datatransmitting rate of 640 Kbit/s of the telemetry sub is realized. On the basis of basiccharacteristics of ultrasonic wave and characteristics of oilfield downhole media, we studied theprinciple and rule of ultrasonic imaging, established logarithmic amplifier math model withbandpass characteristics, designed the proper key electrical units such as preamplifier andlogarithmic amplifier and developed ultrasonic imaging logging tool-acoustic calipersuccessfully.According to magnetic domain theory, the ferromagnetic components are co-pressed byoutside stress and geomagnetic field, so it triggers the orientation of magnetic domainorganization along the geomagnetic field in the stress condensed area and irreversiblereorientation and keeps this irreversible-change status after the stress is eliminated, and itpresents on the surface of components in faint magnetic leakage field forming the metalmagnetic memory characteristics. The magnetic dipole equivalence model is established inmechanism study of metal magnetic memory inspection, the physical calculation way ofinspecting the magnetic memory signal is deduced and the principal of magnetic memoryinspection is physically simulated in a micro strip magnetic way. On the basis ofmagnetostriction equation set of ferromagnetic material, the equation set of magnetic memory isdeducted, and the magnetic memory phenomenon is explained. Effects of stress and geomagneticfield on the magnetic memory are discussed. The paper developed Db4 wavelet filter noiseelimination method applying to eliminate the noise in the signal of magnetic memory accordancewith the basic principal and property of wavelet analysis and the basis characteristics ofmagnetic memory. The cases proved that Db4 wavelet filter noise-eliminated method couldeliminate the effects of various noise in magnetic memory signal, and can identify the stresscondensed area accurately according to the magnetic memory gradient curve after treating.Through many experiments of forcing on the casing and testing, the good relationship betweenthe stress pressed on the casing and the signal of magnetic memory is found. The stress state ofcasing can be evaluated into one of several grades with the method of magnetic memory testing.