Current technology offers the operators of well-intervention equipment little opportunity to receive accurate and real-time visual feedback from the borehole when the fluid contents are opaque. As a result, the majority of operations are performed 'blind' leading to extensive use of time and increased risk of material damages. In extreme cases, and in the pursuit of a clear image the well's contents must be displaced and replaced with fluids that offer better visibility for video cameras at the possible expense of well integrity.
Previous work within the field of borehole imaging has focused upon optical cameras, ultrasound and millimeter-wave technologies. Ionizing radiation is not perturbed by the optical opacity of the well contents or refracted and distorted by flowing fluids. The paper provides detailed results of data gathered from laboratory and field testing. In addition, the paper illustrates images of objects located in a drilling-fluid-filled well. The information provided offers an overview of a new technology and method, which solves the issues surrounding in-hole imaging of infrastructure, well-integrity inspection, and lost or stuck items without the need to displace the well contents.
An overview of the development efforts involving the creation of a borehole tool which aims to solve the issue of through mud imaging, or imaging in a producing well without the need to displace the current contents to an optically clear fluid. The paper gives an overview of the steps necessary to mitigate the risk of such a development project, and an overview of the most important lessons learned. Imaging of backscattered ionizing radiation can find applications within well integrity inspection, perforation inspection, well auditing and the location and orientation of lost or stuck items within the borehole.
One of the major financial concerns voiced by the drilling industry is lost time due to unplanned events such as items lost or stuck downhole in addition to well integrity issues. A number of companies have launched a series of major initiatives that have seen the number of such incidents fall substantially; however, the problem has not been completely possible to eradicate (Fowler, 1996).
Drill string or a downhole tool stuck in a well can prove to be expensive, not only due to possible material damages but due to lost time. Not only are the increasingly sophisticated array of downhole tools and the time lost using them costly, but also the inability to retrieve them could realistically result in the loss of a well.
A common precursor to a fishing expedition is lowering a lead block into the hole and taking an impression of the end of the fish to give the engineers some idea about the best fishing tool to select in order to remove the snapped drill strings or other items. The problem is, however, there is still a distinct challenge in interpreting these impressions and unless the identity is obvious, the impression can be discarded (Walker, 1984).