基于熵权法的气液界面监测评价方法及应用OA

Throughout the full lifecycle of underground gas storage—including construction,capacity expansion,and cyclic injection and production—the dynamic evaluation of the gas-liquid interface remains a key research focus and technical challenge.Accurately quantifying the temporal evolution of gas saturation is of significant importance across different operational stages of gas storage development.During the early construction phase,thermal neutron imaging logging often suffers from insufficient interpretation accuracy and poor computational sensitivity under conditions of low gas saturation and low formation water salinity.To address these issues,this study leverages the response mechanism of thermal neutron imaging logging and selects three key sensitive parameters:long-space count rate,short-space count rate,and formation thermal neutron capture cross-section.The entropy weight method is employed to objectively determine the contribution weights of these parameters to gas saturation.A gas-liquid saturation sensitivity factor is thereby constructed,and a quantitative gas saturation calculation model tailored for the early-stage development of gas storage reservoirs is established.The proposed method effectively suppresses interference caused by low formation water salinity and fluctuations in neutron tube yield,significantly enhancing the detection sensitivity to weak gas-phase signals and improving the precision of gas-water interface delineation.Applied to 18 wells'operation during the initial construction phase of the M oilfield-based gas storage,the approach enabled the establishment of a quantitative evaluation standard and interpretation chart for monitoring wells.Thresholds for classifying six reservoir types—including gas zones and gas-water transition zones—are clearly defined,leading to the cumulative identification of seven effective gas-bearing layers with a total thickness of 21.8 meters.Single-well validation demonstrates that the interpretation results from the new method show excellent agreement with temporary gas production test rates and gas inflow profiling,achieving a correlation coefficient of 0.93.This study confirms that the method exhibits strong adaptability and robust anti-interference capability.It effectively solves the problem of low sensitivity in saturation evaluation caused by low gas content and severe water-phase interference in the initial stage of gas storage construction,provides reliable technical support for gas-liquid dynamic monitoring in the initial construction stage of water-flooded gas storage.