摘要
Abstract
During old-well re-evaluation,constrained by early-stage logging technologies and complex geological conditions,most old wells only retain conventional well-logging curves,without high-precision special logging data such as nuclear magnetic resonance and array acoustic logging.Limited accuracy of fluid identification using conventional logging leads to some potential reservoirs being misinterpreted as dry layers,water layers or uninterpreted zones.Aiming at the identification challenges of low-porosity and low-permeability reservoirs,including ambiguous logging responses,strong interferences from lithology and organic matter,and nonlinear superposition of multiphase-fluid responses,this paper proposes a gas layer identification method using superimposed area coefficients based on a multi-parameter weight model.A three-level progressive discrimination workflow is adopted in this method.At the reservoir screening stage,non-reservoir beds such as mudstone interbeds are eliminated via the superimposed area of gamma-ray and acoustic transit time,and lithology-sensitive evaluation indicators are established.At the fluid-property discrimination stage,a fluid identification index is constructed using the superimposed area of acoustic transit time and resistivity to quantify the response differences between gas-bearing reservoirs and water layers.At the gas layer identification stage,the superimposed area of neutron and density porosities is applied to effectively distinguish gas beds from oil beds.A comprehensive gas layer identification model is established by fusing the three types of superimposed-area characteristic parameters with the weight-coefficient method.Field application results show that the overall interpretation coincidence rate of the proposed model reaches 78.3%for verification wells in the study area,and its identification accuracy outperforms conventional gas layer discrimination methods.Converting the traditional static-parameter threshold discrimination into multi-parameter dynamic area-coupling analysis,this technique greatly improves the logging interpretation accuracy for complex gas reservoirs,and provides a low-cost and high-efficiency technical approach for tapping gaslayer potential in mature oil-gas areas.关键词
老井复查/常规测井/权重系数法/气层识别Key words
old well re-evaluation/conventional well-logging/weight coefficient method/gas layer identification分类
能源科技
