The technology known as downhole television logging, also referred to as borehole wall ultrasonic imaging, utilizes ultrasonic wave reflections from the well wall or casing inner wall to analyze the well's profile. This technology has two main applications in the field of oil drilling. In open-hole wells, it can be utilized to detect fractures in rock formations, measure the dimensions of the wellbore, determine hole size, assess the apparent inclination and orientation of formation fractures, and qualitatively identify lithology. In cased wells, it is used to precisely measure changes in casing inner diameter, detect casing rupture, misalignment, corrosion, and assess perforation quality. Additionally, it allows for observation of casing couplings.
Application of ultrasonic television logging in cased wells：
Detection of Casing Corrosion
Downhole TV logging is a valuable tool for identifying casing corrosion as it can distinguish between pitting and sheet corrosion. This technology provides accurate insights into the shape, degree, and remaining wall thickness of the corrosion.
Casing coupling inspection
In the figure, the black horizontal line at the well depth of 1965.18~1965.56m is the casing coupling. Each well has a special coupling as a mark of the well depth. It is very convenient to use ultrasonic imaging to observe couplings, find casing pup joints, and adjust the depth at the pup joint.
Detection of casing deformation and explosion shaping effect
The impact of shaping can be easily observed through ultrasonic imaging logging tools. The figure clearly shows that the casing has been twisted and distorted, with the casing expanding in the explosion shaping area at a depth of 1883.0~1886.0m. A three-dimensional histogram reveals significant corrosion in the 1881.0~1884.0m section of the well. Additionally, it is evident that certain areas have suffered blowouts. The maximum well diameter reaches 200mm, surpassing the casing's outer diameter of 139.7mm.
Application of ultrasonic video logging in fracture evaluation:
This image shows the identification of fractures in the exposed portion of the well. Analysis of ultrasonic TV data revealed a correlation between the formation of fractures in the well and the type of rock. Basic and intermediate-basic igneous rock formations are more likely to develop large vertical fractures and high-angle fractures. These fractures eventually connect to form reservoirs that are conducive to oil or natural gas storage.
It is obvious that underground television plays an important role in oil and gas exploration and development and has great economic benefits.
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