NIR Technology Australia

Application Note 73: Calibration of Formate Stabilizer levels in Sodium Formate Mud using an NIT-38 Alcohol Analyser.

March 2006.

Introduction:

Sodium Formate Mud is a synthetic based mud that is used as a drilling fluid. The use of synthetic based mud’s compared to the more common water based mud’s is preferable due to it’s performance in difficult areas, such as, drilling in reactive shales, deep bore drilling and extended-reach drilling. The need for a quick portable testing system to analyse the stabilizing agents in the mud to ensure it is operating efficiently is required.

This study was undertaken to demonstrate the feasibility of measuring formate stabilizer levels in sodium formate mud solutions. The NIT-38 Alcohol Analyser was used for the purpose of this study.

Procedure:

6 samples of Sodium Formate Mud were supplied. The liquid solutions were then placed in a liquid test cell and scanned over the wavelength range of 720nm to 1100nm at a pathlength of 20mm. A total of 10 scans were collected and each sampling was repeated and presented to the instrument twice. The spectra was collected and then uploaded into NTAS (NIR Technology Australia Software) and Partial Least Squares Regression (PLS) was used to develop a calibration for Formate Stabilizer levels.

Results:

Figure 1, below, shows the NIT spectra of the 6 samples of pyrethrin solutions.

Figure 1: Plot of NIR Spectra for scanned Sodium Formate Mud solutions.

Figure 2 shows the calibration statistics for the NIR Formate Stabilizer values versus the reference Formate Stabilizer value. The Standard Error of Calibration is 0.15 with a correlation (R²) of 0.99.

Figure 2: Plot NIR Formate Stabilizer value vs. Reference Formate Stabilizer value.

After creating the calibration, 6 samples were retested, in duplicate and plotted. Figure 3, below, show the results of this testing giving a Standard Error of Prediction 0.07 and a correlation (R²) of 0.99.

Figure 3: Plot NIR Predicted Formate Stabilizer value vs. Reference Formate Stabilizer value.

Conclusion:

It can be seen in figure 2 that the NIT-38 Alcohol Analyser can be calibrated to measure the Formate Stabilizer levels. However, the sample set is too small for a truly robust calibration even with the wide range of available samples.

The Standard Error of Calibration for the trial set was 0.15 with additional samples this error could potentially be reduced. The correlation of 0.99 clearly shows the high level of potential with in this application. When using the trial calibration to predict against samples it was shown that the true error was actually 0.07.