Carbon Nanotube Gamma-Ray Detector For Use As An Imaging Device For Use In An Oil Or Gas Well

Schlumberger Technology Corporation (Sugar Land, TX) received U.S. Patent 7,767,958 for a carbon nanotube gamma-ray detector for use as an imaging device for use in an oil or gas well or the like. Examples of imaging devices include medical imaging devices, fluid flow imaging devices, and devices for the nondestructive imaging of materials. 

The detector is comprised of: a housing having a window through which gamma rays can enter; the housing comprising; a two-dimensional array of electrically conducting carbon nanotubes, which act as a cathode, on a substrate; a metal plate electrode, which acts as an anode, positioned opposite the substrate so that there is a gap containing a gas between the electrode and the nanotubes.  A voltage source connected to the substrate and the electrode such that when in use the voltage between the substrate and the electrode is maintained below the arc-threshold voltage so that no electric current can flow through the gap between the nanotubes and the electrode; wherein the electrode and the substrate are arranged such that when a gamma ray enters the housing and hits one of the nanotubes a spark discharge is triggered between the nanotubes and the plate electrode creating an electrical current that can be measured, according to inventors Anthony Veneruso Martin Luling and Gilles Mathieu.

 Gamma-ray measurements serve to detect radioactivity, whether it is from natural background radiation or from artificially created and deployed sources. They are used in many industries, such as non-destructive testing and inspection of materials and equipment, medicine, geologic (i.e., mineral) exploration, as well as in oil and gas exploration.

In oil and gas exploration, gamma-ray measurements can be used to determine the properties of formations surrounding wells. Gamma ray tools are used to measure density, porosity, photoelectric factor (Pe), hydrogen index, salinity and thermal neutron capture cross section (sigma). 

FIG. 1 (a) shows a schematic diagram of a nanograss patch and (b) a SEM photo of a nanotube arrangement