基于阵列声波测井技术的海上砂岩储层压裂效果评价方法

Evaluation of Fracturing Effects in Offshore Sandstone Reservoirs Based on Array Acoustic Logging Technology

  • 摘要: 为满足海上砂岩储层压裂效果评价需求,基于压裂前后测量的阵列声波测井资料,研究并应用了纵波层析成像技术和偶极散射波技术进行储层压裂效果评价。纵波层析成像技术可以重建井壁附近地层径向声速剖面,通过对比压裂前后井壁附近地层声速的径向变化,可以评价近井壁储层水力裂缝的高度,但无法评价远井处储层的压裂效果;偶极散射波技术利用散射波能量分析井孔周围数十米范围内地层的非均质性,可以评价远井处水力裂缝的空间展布情况。上述2种技术相结合,可实现对储层近井壁和远井壁地层压裂效果的综合评价。采用该方法评价了海上调整井X1井的压裂效果,与压裂前相比,压裂后近井壁形成的裂缝使岩石声速明显降低,水力裂缝高度约为13.80 m,井周裂缝形成的散射波能量差异区域显示,在井眼周围至少14.00 m范围内形成了明显的压裂体积改造,说明压裂效果良好。该方法不仅可以准确判断近井壁和远井处水力裂缝的高度,还可以在一定程度上评价水力裂缝的径向长度。

     

    Abstract: In order to comply with the requirement to evaluate fracturing effects in offshore sandstone reservoirs, the application of P-wave tomography imaging technology and dipole scattering wave technology for fracturing effect evaluation of reservoirs were studied based on array acoustic logging data measured before and after fracturing. P-wave tomography imaging technology can rebuild the radial acoustic velocity profile of the formation near the borehole. By comparing the radial acoustic velocity changes of the formation near the borehole before and after fracturing, the reservoir fracturing height near the borehole can be evaluated, but the fracturing effect of the formation away from the borehole cannot. The dipole scattering wave technology uses the scattering wave energy to analyze the formation heterogeneity within tens of meters around the borehole. It can evaluate the spatial distribution of fractures away from the borehole. The combination of the above two technologies can accomplish the comprehensive evaluation of the fracturing effect of the formation near and away from the borehole. It has been applied in the fracturing Well X1 of the offshore sandstone reservoir. Compared with that before fracturing, the rock acoustic velocity was significantly reduced by the fractures created after fracturing near the borehole, and the fracturing height was about 13.80 m. Meanwhile, the difference area of scattered wave energy formed by fractures around the borehole showed that obvious fracturing volume stimulation was formed in the range of at least 14.00 m around the borehole, indicating that the fracturing effect was good. This method can not only identify the fracture heights of reservoir fracturing near and away from the borehole but also evaluate the radial length of the fractures to a specified extent.

     

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