Application Research of the Combination Technology of MTD-G Electromagnetic Defectoscope Logging and Ultrasonic Lamb Wave Imaging Logging in Complex Casing Damage Wells

In the block of long-term oil and gas production, well cement and casing are comprehensively affected by formation creep, geo stress evolution, corrosion, sand production erosion, and other external factors for a long time, which will lead to a great difference from the original state. In the later period of oilfield production, the issue of comprehensive management of low-production and low-efficiency wells is particularly prominent, often requiring sidetracking drilling operations to develop the potential. Accurately identifying real-time cement sheath cementing quality and quantitatively analyzing casing deformation are crucial for wellbore abandonment, and sidetrack drilling operations. Conventional radial cement bond logging cannot identify the absence of circumferential cement outside the casing, while conventional acoustic logging can only detect damage to the inner wall of the casing and cannot detect damage to the outer and outer casing walls. The Bohai Oilfield has combined MTD-G electromagnetic defectoscope logging and ultrasonic lamb wave imaging logging technology to form an engineering logging technology method for evaluating the casing damage of multi-layer casing strings in complex well conditions. The new technology has been applied and verified in Well A of Bohai Oilfield, and the results show that the monitoring results of the 9–5/8″ casing are consistent with the conventional logging interpretation. The detection of 13–3/8″ casing with new technology shows that there is strong damage in the 13–3/8″ casing from 337m to 340 m, with a minimum wall thickness of 7.91 mm. The metal loss rate in other casing sections is below 10%. The testing results of cement outside the 13–3/8″ casing indicate that the overall cementing quality of the external cement is good to medium, but there is a small amount of liquid distributed inside the cement. This method can quantitatively analyze the corrosion, wear, deformation, and eccentricity of underground casing strings, and accurately evaluate the damage status of the cement sheath outside the casing. It is of great significance for studying the damage situation of multi-layer casing and cement in complex wells.