During well intervention activities, one of the biggest challenges faced is uncertainty about the downhole hardware. Carrying out interventions without understanding the state of downhole equipment can be time-consuming, expensive and ultimately unsuccessful. There are several diagnostic techniques available to assess the state of downhole hardware, but none offer an efficient and reliable solution, particularly if the well fluid is opaque. Recently, an X-ray based wireline tool was introduced for providing downhole imaging, regardless of the well fluid. We will present a case study in which this new tool was run in a brine-filled onshore gas storage well in the Netherlands. In this case, the X-ray images provided measurements of the inner- and outer-diameters of a coiled tubing disconnect to millimeter-scale accuracy. These X-ray images and measurements verified the operator's fishing plan and they successfully retrieved the fish on the first attempt. In general, the quick and reliable visualization of downhole objects provided by X-ray imaging reduces the uncertainty and concomitant risk associated with well interventions, resulting in a higher success rate, less downtime, and lower cost.