Acta Photonica Sinica, Volume. 52, Issue 3, 0352112(2023)
Quantitative Analysis Method of Multi-elements for Logging Cuttings Based on LIBS Technology(Invited)
It is one of the basic works to determine the elemental contents of cuttings' samples from different depths in the process of oil and gas exploration and development. An accurate element logging map can provide significant information for identifying lithology, predicting the formation to be drilled, selecting suitable drilling parameters and reducing drilling risks. With the disadvantages of complex operation processes, complicated sample pretreatment and long analysis time, most traditional element analysis technologies are difficult to meet the requirements of rapid analysis for cuttings at thelogging site. In recent years, X-ray fluorescence spectrometry technology has been widely used in the logging field for real-time online element analysis due to its portability, low sample demand and fast detection speed. However, based on its technical principles, XRF has a certain radiation risk, and it is poor to detect light elements (atomic number < 11). As a promising analytical technology, laser-induced breakdown spectroscopy technology has the advantages of real-time, in-situ, simple structure and multi-element simultaneous analysis, which meets the actual need of rapid analysis for cuttings logging. The experimental system used in this study was a self-developed benchtop laser-induced breakdown spectrometer, mainly consisting of a Nd: YAG laser, three spectrometers, a digital delay generator and several optical fibers and lenses. A total of 1320 LIBS spectra of 66 rock samples, including 49 Chinese national standard rock samples as training samples and 17 supplementary samples as test samples, were collected by the instrument. The characteristic peaks including 288.16 nm (Si Ⅰ), 308.22 nm (Al Ⅰ), 445.48 nm (Ca Ⅰ), 516.73 nm (Mg Ⅰ) and 769.90 nm (K Ⅰ) were selected as target peaks for quantitative analysis. To improve the data stability and repeatability, a part area normalization was proposed. Different from total area normalization, only considering18 characteristic spectral lines of 9 main elements in rocks, part area normalization could take into account the mapping relationship between the spectral line intensity and content of the element, reduce the spectral difference caused by the inconsistent ablative amount and weaken the influence of matrix effect. Based on the training data set, the appropriate data pretreatment method was selected from three normalization methods (including min-max normalization, total area normalization and part area normalization) for each element. To improve the quantitative accuracy, a coefficient correction method based on a principal component regression algorithm was proposed to correct the characteristic peak intensity. On the basis of the calibration curve of peak intensity after normalization and content established for each element, the ideal peak intensity and correction coefficient between peak intensity corresponding to different content could be calculated. PCR algorithm was used to establish models for calculating correction coefficients with the input of the full spectrum data. Then, the quantitative analysis models for five target elements were established upon the corrected peak intensity data. The test data set was applied to evaluate the quantitative models. The coefficients of determination (
Get Citation
Copy Citation Text
Sha CHEN, Yanting YANG, Xu WANG, Qingwen FAN, Yixiang DUAN. Quantitative Analysis Method of Multi-elements for Logging Cuttings Based on LIBS Technology(Invited)[J]. Acta Photonica Sinica, 2023, 52(3): 0352112
Category: Special Issue for Frontiers and Techniques of Laser Spectroscopy
Received: Oct. 12, 2022
Accepted: Nov. 29, 2022
Published Online: Jun. 21, 2023
The Author Email: FAN Qingwen (fanqingwen@scu.edu.cn), DUAN Yixiang (yduan@scu.edu.cn)