The Application of Downhole Laser Raman Spectroscopy Technology in Coalbed Methane Wells in Eastern Ordos Basin

The downhole reservoir laser Raman spectroscopy system (DRRS) is growing to be an essential tool for in-situ and online detection of natural gas in reservoir. It is non-destructive, fast and accurate, and provides a significant method for direct gas identification and measurement and highly efficient development of unconventional gas reservoirs. This paper introduces development history and the basic principles of laser Raman spectroscopy technology, and also introduces the application effect of this technology in coalbed methane (CBM) wells in the Eastern Ordos basin. The test results showed that only methane was detected in the target coal seams, and that the relative gas content of individual layers was in high agreement with the results of gas chromatography, which was widely used in natural gas testing, differing by only 1% in the same layer, confirming the reliability of the new technique. Tests on both wells indicated that the most potential area was in the area controlled by well B, with the favorable layer being the Shanxi formation with a 9.27 mol gas content; the distribution law of the gas content in the area can be obtained from multi-well testing, which will provide a more perfect basis for fine exploration and development. The application of DRRS shows that the equipment can identify the composition of natural gas qualitatively in situ and quantitatively detect the relative content of natural gas reliably. However, in order to popularize this technology, the current data processing module needs to be improved so that the absolute values of the test can be directly compared with gas chromatography.