基于依赖频率AVO反演的高含气饱和度储层预测方法

摘要

Elastic parameters obtained by conventional preor post-stack inversions are not sensitive to gas saturation of reservoirs.Therefore,we use dispersion parameters obtained by frequency-dependent AVO inversion to predict high gas-saturation reservoirs.First the influence of sand-reservoir saturation on viscosity of different fluid mixtures is analyzed with Refutas equation; and the influence of gas-saturation on velocity dispersion and attenuation is analyzed with the dynamic equivalent- medium theory and Woods formula.Then the frequency-dependent AVO inversion is achieved based on f-μ-ρ AVO approximation;and the sensitive dispersion factor is optimized.The following phenomena are obtained in results:①Different fluids have different dispersion and attenuation,and dispersion and attenuation are dependent on water or gas saturation; ②The optimized dispersion factor is more sensitive to high gas-saturation reservoirs and less affected by the background,which can accurately depict the spatial disdistribution of high gas-saturation reservoirs.%常规的叠前或叠后反演得到的弹性参数对储层含气饱和度的敏感性很弱,较难识别高含气饱和度有效储层.为此,利用依赖频率的AVO反演得到的频散参数预测高含气饱和度的有效储层.首先引入Refutas公式,分析了饱和度对混合流体黏度的影响,结合动态等效介质理论和Wood公式,分析了含气饱和度对速度频散和衰减的影响;再基于f-μ-ρ 反射系数公式,实现了依赖频率的AVO反演,并优选了敏感频散因子.结果表明:①不同流体的频散和衰减程度不同,并且依赖含水(含气)饱和度的变化;②优选的频散属性对流体储层具有很强的敏感性,且受背景干扰小,可以精确地刻画高含气饱和度储层的空间分布位置.