测井资料定量计算天然气藏中CO_2含量

Quantitative Calculation of CO_2 Content in Natural Gas Reservoir with Log Data

莺歌海盆地中央坳陷北部区域储层高温高压条件下,中子测井中岩石和流体骨架取值的不确定性严重影响该区CO_2含量的计算精度。在利用体积物理模型结合阿尔奇公式较准确计算出地层孔隙度和饱和度的基础上,利用中子长源距计数率对CO_2气层响应较为敏感的特性,建立了利用长源距计数率值、气体平均含氢指数预测CO_2含量的模型,较准确地预测了CO_2气体在目的层的相对含量。该方法能够有效克服地层物性、含水饱和度等因素对CO_2计算精度的影响,计算误差小于10%,在现场应用中取得了良好的效果。

Because of the influence of high temperature and overpressure environment of Yinggehai basin central depression, the methane and CO2 gas make little contribution to resistivity of formation water.The accuracy of the region CO2 content that is quantitatively calculated on the physical volume model is seriously affected by uncertainty of rock and fluid matrix value of neutron logs.With the Archie formula and physical volume model to more accurately calculate the porosity of formula, CO2 gas reservoir is identified by the long and short neutron source spacing logging counting rate response difference between the methane and CO2 gas reservoir measurements.Then established is statistic relation between long-short counting rate and gas mean hydrocarbon index, helping to do CO2content prediction.Comparing with the old methods, the practical application of this method shows better CO2 identification capability and quantitative calculation accuracy.