黏土对蒸馏抽提法密闭取心样品饱和度影响分析OA

Measured oil and water saturations from sealed core samples are the fundamental data for reservoir oil-bearing evaluation.However,for montmorillonite-rich formations,when the Dean-Stark distillation method is used to determine core fluid saturations,the structural water within montmorillonite releases during high-temperature distillation,causing systematic overestimation of the measured water saturation,and the laboratory saturation results cannot truly reflect the original underground formation state.To quantitatively evaluate the interference of clay minerals on saturation measurements obtained by distillation,this study takes the Minghuazhen formation of Bohai B oilfield as the research object,selects four mudstone cores to carry out variable-temperature thermogravimetric tests,and quantitatively characterizes the release characteristics of bound water and interlayer water in different mudstone samples.Based on the rock volume physical model,combined with clay content and clay-water loss ratio,a clay correction method for saturation is established for shaly sandstone reservoirs.The experimental results show that the clay-water loss characteristics of mudstones under the same sedimentary environment are stable;at the standard Dean-Stark distillation temperature(116℃),the clay-water loss percentage is 20.1%.After simultaneously performing clay correction and fluid loss correction,the corrected core water saturation matches well with the MICP and well log interpretation results,and the absolute error can be controlled within-5%～5%.This correction method effectively solves the problem of distorted fluid saturation measurement in montmorillonite-bearing shaly sandstone reservoirs and can provide technical support for accurate evaluation of oil-bearing properties in similar reservoirs.