致密砂岩储层贝叶斯岩性判别与孔隙流体检测

Bayesian lithofacies discrimination and pore fluid detection in tight sandstone reservoirs

应用统计岩石物理方法可以定量预测地下岩性和储层孔隙流体分布。根据川中致密砂岩储层的特点,本文选用纵波阻抗和横波阻抗进行二维贝叶斯分类。井数据分类结果表明,利用纵波阻抗和横波阻抗可以较好地区分各种岩性,甚至可以初步识别孔隙流体。因此,将该分类技术运用到反演的地震属性中,得到了目标层段、围岩及储层孔隙流体在横向上的分布。预测的岩性分布基本上反映了目标层位的沉积特点,含气砂岩主要分布在须二段砂体的内部并且在B井两侧富集。

Applying statistical petrophysics can quantitatively predict the distribution of subsurface lithofacies and pore fluid in reservoirs.According to the characteristics of tight sandstone reservoirs in the Central Sichuan,P-wave and S-Wave impedances were selected for 2-D Bayesian classification in this paper.Classification results of well data show that using P-wave and S-wave impedance could distinguish lithofacies,even preliminarily recognize pore fluid.Therefore,applying this classification technique to invert seismic attributes,we obtain the lithology lateral distribution and pore fluid around targets.The predicted lithofacies distribution reflects basically sedimentary characteristics of targets.Besides,gas bearing sandstones distribute mainly in the interior of the Formation Xu 2 and concentrate around Well B.