Drilling Fluid Activation Correction in LWD Gamma Ray Logging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Natural gamma ray logging measurements are biased by drilling fluid activation-induced gamma rays, particularly oxygen activation, which current correction methods are prone to errors due to varying contributions of mud-based gamma rays during logging operations.
Innovation Solution
A method involving a neutron source and natural gamma ray sensor in a logging while drilling string, which acquires spectral gamma ray measurements to compute first and second drilling fluid activation corrections using different methodologies, and applies a weighted average correction to obtain accurate total natural gamma ray measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single correction methodology is used for drilling fluid activation, then the correction process is simple, but measurement accuracy deteriorates due to varying contributions of mud-based gamma rays
Solution Approach 1:
The correction process is divided into multiple independent correction methodologies (first correction for initial gamma ray contributions, second correction for additional gamma ray contributions). Each correction method processes specific portions of the gamma ray spectrum separately, allowing for more accurate compensation of drilling fluid activation effects while maintaining clear computational boundaries
Solution Approach 2:
The correction methodology dynamically adjusts correction parameters based on measured gamma ray energy distributions. By monitoring changes in gamma ray spectral parameters and applying different correction factors for different energy ranges, the system adapts to varying mud activation conditions throughout the logging operation
2Reliability
If drilling fluid activation corrections are applied, then measurement bias is reduced, but correction errors increase due to varying mud gamma ray contributions
Solution Approach 1:
The correction system continuously adapts to changing drilling conditions by dynamically adjusting correction parameters based on real-time gamma ray spectral measurements. As mud composition, circulation patterns, or neutron flux vary during logging, the system modifies its correction approach accordingly, ensuring reliable and accurate measurements throughout the operation
Solution Approach 2:
The correction methodology incorporates feedback mechanisms where measured gamma ray energy distributions are continuously monitored and used to adjust correction parameters. The system compares expected versus actual spectral signatures and refines correction factors based on the observed deviations, improving both reliability and precision
Data Source
AI summary
A method for making natural gamma ray measurements of a subterranean formation includes causing a natural gamma ray sensor on an LWD tool to acquire a spectral gamma ray measurement while a neutron source emits neutrons. The measurements are evaluated to compute first and second drilling fluid activation corrections using corresponding first and second correction methodologies. The first and second corrections are processed to compute a third drilling fluid activation correction which is applied to the gamma ray measurements to compute a corrected total natural gamma ray measurement.