Abstract: The salinity of formation water used to be normally measured in laboratory with in-situ formation water sample. The acquired formation water sample only characterizes in-situ movable water rather than unmovable water, both of which there possibly exists distinct difference in salinity. Particularly, such a difference may appear much bigger than before following water flood development of an oilfield. At the result, the measured salinity from the water sample is hard to reflect the total salinity of formation water comprehensively and accurately, thus leading to detrimental effect of corresponding well log interpretation. This study presents a more accurate thought or method for determination of the salinity of formation water, and better results have been gained followed by application of it in Qiuling oilfield.

Key words: formation water, salinity, core, well log interpretation