| 摘要 |
An apparatus for measuring the density of a subterranean formation from within a wellbore, especially a cased wellbore. The apparatus has an energy source configured to generate 14 MeV of neutrons in pulses of 20 microseconds or less. The apparatus has at least three detectors for detecting gamma rays which are produced as a result of the neutron pulse. The detectors and energy source are aligned along a central axis with the energy source being at one end. Shielding is disposed between each of the three detectors and between the end detector and the energy source adjacent to it. The detectors are configured to measure gamma rays below 700 KeV and generate a signal in response thereto. The signals may then be compared to predetermined characteristic signals or computer simulations to determine the density, and hence porosity, of the formation.
|
