Gamma ray detectors with gain stabilization

摘要

Systems and methods for measuring natural gamma rays in a wellbore are disclosed that involve using a downhole gamma ray detector that provides signals that scale with energy deposited by gamma rays in the downhole gamma ray detector and storing digital signals in channels. A derivative of the digital signals is taken and the location of the maximum value of the derivative is used to stabilize the gamma ray detector by adjusting the threshold or gain based on the maximum value of the derivative or adjusting an amplifier or variable high voltage source. Other systems and methods are presented.

主权项

1. A system for measuring natural gamma rays in a wellbore, the system comprising:
a downhole gamma ray detector that provides signals that scale with energy deposited by gamma rays in the downhole gamma ray detector; an electronics unit electrically coupled to the downhole gamma ray detector for converting the signals including preparing digital signals; a processing unit electrically coupled to the electronics unit, wherein the processing unit comprises one or more memories for storing data or instructions and one or more processors associated with the one or more memories; wherein the electronics unit and processing unit are operable to sort the digital signals from the downhole gamma ray detector into channels according to amplitude of the digital signals and storing the sorted digital signals as an energy spectrum; and wherein the one or more processors in association with the one or more memories is configured to:
take a derivative of the digital signals stored in the channels, locate a maximum value of the derivative of the digital signals, and sum counts of the digital signals in the channels above a threshold based on the location of the maximum value of the derivative of the digital signals.