Application of X-ray fluorescence logging technique in lithologic identification:A case study in wells YB10 and YB22, Yuanba region, northeast Sichuan Basin

New techniques such as air drilling,PDC and impregnated bit + fast-spiral screw have been practiced widely in Yuanba region of the northeast Sichuan Basin;however,fast drilling and fine or even powdered detritus have made it difficult to identify lithologic characters and formation boundaries for common well-logging.The X-ray fluorescence logging technique is not restricted by small detritus size or short analysis period.It deals with the contents of 14 elements such as Mg,Al,K,Si,S,Ca and Fe in rock samples so as to analyze lithologic features and to identify formation boundaries.The new technique was practiced in well YB10.4 115 samples collected from 702-7155 m deep were analyzed.According to element contents and curve changes,combined with outcrop lithologic data,continental sandstone and mudstone as well as marine carbonate rock were distinguished.The results were accordant with electric logging data in 92.60%.