ARMAS, MériemeDr. CHOUAT Nadjat2025-07-152025-07-152025http://dspace.univ-temouchent.edu.dz/handle/123456789/6673This thesis focuses on the quality control of liquefied natural gas (LNG) composition analysis carried out at the GL3/Z complex of Sonatrach in Bethioua. The study specifically addresses the management of analytical deviations in the gas composition analysis using gas chromatography, according to the ASTM D1945 standard. The main objective is to implement a statistical process control approach. A reference gas was injected 30 times to establish baseline averages and standard deviations for each component. These values were then used to analyze 24 weekly injections, aimed at detecting any significant drift in the analytical system. The results showed good stability and repeatability, with measured concentrations remaining within acceptable limits. This work contributes to strengthening metrological control and supports a broader quality assurance strategy aligned with ISO/IEC 17025 requirements.frThesis