阵列声波测井技术在火山岩储层评价中的应用

Application of array acoustic logging technology in volcanic reservoir evaluation

为精细评价四川盆地二叠系火山岩储层有效性与含气性,针对阵列声波测井资料开展深入研究。建立了基于斯通利波衰减与反射波信号和纵波速度层析成像技术的储层有效性评价方法,利用阵列声波计算的岩石力学参数形成储层流体性质判别方法,最后,通过偶极横波远探测对井旁缝洞发育程度进行了定量表征,为单井测试结果分析提供合理解释。研究结果表明:①四川盆地火山岩储层主要岩性为火山碎屑岩,储层物性好,斯通利波能量衰减明显,反射系数高,且低频段反射系数比高频段高,地层声速有较明显径向变化,到时曲线滞后明显,反映储层渗透性强、有效性好;②当地层含气时纵横波速度比降低,泊松比降低而体积模量增大,利用泊松比和体积模量交会产生的包络面积可以有效判别储层含气性;③偶极横波远探测成像图显示T2井储层段井外发育有高角度过井裂缝,为地层水流动提供了通道,导致气层段测试产出地层水。

To finely evaluate the effectiveness and gas potential of volcanic reservoirs of the Permian in the Sichuan Basin,an in-depth study was conducted on array acoustic logging data.A method for evaluating reservoir effectiveness was established based on the Stoneley wave attenuation,and reflection wave and P-wave velocity tomography.And a method for discriminating reservoir fluid property was developed using the rock mechanical parameters calculated from array acoustic data.Finally,the development of frac-tures/vugs near wellbore was quantitatively characterized by dipole S-wave remote detection,providing reasonable interpretations for single-well testing.The research results are as follows:(i)Volcanic reservoirs in the Sichuan Basin are mainly composed of volcani-clastic rocks,characterized by good reservoir properties,significant Stoneley wave attenuation,high reflection coefficient(higher in the low-frequency interval than in the high-frequency interval),obvious radial variation of acoustic velocity in formation,and signif-icant hysteresis of the arrival time curve,reflecting strong permeability and good effectiveness of reservoir.(ii)When the formation contains gas,the velocity ratio of P wave to S wave decreases,the Poisson’s ratio decreases while the bulk modulus increases.The en-velope area derived by the intersection of Poisson’s ratio and bulk modulus can effectively discriminate the gas potential of reservoir.(iii)The image of dipole S-wave remote detection shows that high-angle fractures are developed outside the interval of Well T2,which provide pathways for formation water,resulting in formation water produced from gas-bearing interval.