Many components used in completions are geometrically complex and machined to tight tolerances. Precisely measuring the internal profile dimensions of these items after installation is impossible using mechanical means such as calipers due to the sharp ID changes precluding good finger contact. This paper will discuss the use of a precision ultrasonic tool that allows accurate measurements to be taken without physical contact, and to detail a case study of inspecting a landing nipple profile.
Mechanical finger type caliper devices cannot measure internal diameters unless physically in contact with the surface and this is not possible at all times. An alternative to physical measurement is to reflect a projected beam of acoustic energy from the target and, knowing the speed of sound of the well fluid, calculate an ID measurement. Using a number of ultrasonic transducers allows beamforming techniques to precisely focus the sound to produce good resolution. The ultrasound tool uses a circumferentially arranged band of 288 sensors that operate in a phased array to determine accurate ID of even very complex profiles.
A landing nipple is a component that is designed for the installation of flow control devices in a well completion and comprises a seal area and a lock profile. The dimensions of these faces are very precisely controlled during manufacture because the device being installed, such a safety valve, must fit perfectly in order to provide a seal and mechanical attachment. If the lock profile, for example, becomes damaged or eroded than there is a chance of the safety valve being ejected from the nipple. The 288 transducer array of the ultrasound tool provides a circumferential spacing of 1.25° between measurements; ensuring even small defects can be detected. Following a laboratory test of a representative landing nipple under controlled conditions to verify the tool performance, a number of landing nipples were inspected in a field where erosion was suspected. The tool was able to accurately map the complex locking profile and to measure the dimensions to within a hundredth of an inch in each case, giving the operator confidence that the correct locks were being used to install the safety valves.
The unique properties of focused ultrasound allow the mapping and verification of even complex machined components while they are still downhole. With 288 circumferential readings, high resolution measurements are possible to an accuracy of a fraction of a millimetre raising the possibility of engineering a solution to a given problem rather than resorting to the expensive option of replacing the completion.