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Rock Physical Modeling and Seismic Dispersion Attribute Inversion for the Characterization of a Tight Gas Sandstone Reservoir
Frontiers in Earth Science ( IF 2.9 ) Pub Date : 2021-03-01 , DOI: 10.3389/feart.2021.641651
Han Jin , Cai Liu , Zhiqi Guo , Yiming Zhang , Cong Niu , Di Wang , Yun Ling

In the rock physical modeling in this study, the complex pore space of tight sands was assumed to be equivalent to the combination of high aspect-ratio pores (stiff pores) and low aspect-ratio microcracks (soft pores). Then, the Chapman theory was used to simulate the elastic properties and inelastic behavior of the dispersion and attenuation caused by the squirt flow of fluids in the complex pore spaces for different gas saturations. The modeling results indicate that as the gas saturation increases, the P-wave velocity decreases at seismic frequencies and dispersion and attenuation occurs at higher frequencies. The velocity dispersion of the tight gas sandstone causes the contrast in the P-wave impedance across the interface between the tight sand and the overlying mudstone vary with frequencies, and thus, the reflection coefficients of the interface are frequency-dependent. The models with different gas saturations in tight sand represent the specific features of frequency-dependent reflection coefficients. The seismic modeling shows that the reflected waveforms have a negative phase when the tight sand is fully saturated with gas and a positive phase when they are fully water saturated. Moreover, these two extreme cases exhibit distinct amplitude versus angle (AVA) features in the seismic reflections. For a scenario between full gas and full water saturation, the reflection coefficients exhibit a more obvious frequency dependence, and polarity reversal occurs in the synthetic AVA gathers. The frequency-dependent AVA inversion using synthetic data revealed that high values of the inverted P-wave dispersion attribute indicate a high gas saturation in tight gas sandstone. There is a significant difference in the inverted dispersion attributes of the two cases of tight sandstone that are fully saturated with gas and with water. Applying the frequency-dependent AVA inversion to the pre-stacked field seismic data revealed that the inverted P-wave dispersion attribute is positively correlated with the gas production from the payzone of the tight gas sandstone. The methods used for the rock physics modeling and the frequency-dependent AVA inversion conducted in this study have good potentials for the evaluation of the degree of gas saturation in tight gas sandstone reservoirs.

中文翻译:

致密气砂岩储层特征的岩石物理建模和地震频散属性反演

在本研究的岩石物理模型中,假设致密砂的复杂孔隙空间等效于纵横比高的孔(刚性孔)和纵横比低的微裂纹(软孔)的组合。然后,用查普曼理论模拟了由于不同气体饱和度引起的复杂孔隙空间中的流体喷流所引起的色散和衰减的弹性和非弹性行为。模拟结果表明,随着气体饱和度的增加,地震频率下的纵波速度会降低,而在较高的频率下会发生弥散和衰减。致密气砂岩的速度色散会导致致密砂岩和上覆泥岩之间的界面上的P波阻抗的反差随频率而变化,因此,接口的反射系数与频率有关。在致密砂岩中具有不同气体饱和度的模型代表了随频率变化的反射系数的特定特征。地震模型表明,当致密砂子被气体完全饱和时,反射波形具有负相位;而当水分完全饱和时,反射波形具有正相位。此外,这两种极端情况在地震反射中都表现出明显的振幅与角度(AVA)特征。对于在充满气体和充满水之间的场景,反射系数表现出更加明显的频率依赖性,并且在合成AVA道集中会发生极性反转。使用合成数据进行的随频率变化的AVA反演表明,反向P波频散属性的高值表明致密气砂岩中的气体饱和度很高。两种致密砂岩在气体和水完全饱和的情况下,其倒置弥散属性存在显着差异。将频率相关的AVA反演应用于叠前的地震数据表明,反P波频散属性与致密气砂岩产层区的天然气产量呈正相关。这项研究中进行的岩石物理建模方法和频率相关的AVA反演方法对于评价致密气砂岩油藏的气饱和度具有良好的潜力。两种致密砂岩在气体和水完全饱和的情况下,其倒置弥散属性存在显着差异。将频率相关的AVA反演应用于叠前的地震数据表明,反P波频散属性与致密气砂岩产层区的天然气产量呈正相关。这项研究中进行的岩石物理建模方法和频率相关的AVA反演方法对于评价致密气砂岩油藏的气饱和度具有良好的潜力。两种致密砂岩在气体和水完全饱和的情况下,其倒置弥散属性存在显着差异。将频率相关的AVA反演应用于叠前的地震数据表明,反P波频散属性与致密气砂岩产层区的天然气产量呈正相关。这项研究中进行的岩石物理建模方法和频率相关的AVA反演方法对于评价致密气砂岩油藏的气饱和度具有良好的潜力。将频率相关的AVA反演应用于叠前的地震数据表明,反P波频散属性与致密气砂岩产层区的天然气产量呈正相关。这项研究中进行的岩石物理建模方法和频率相关的AVA反演方法对于评价致密气砂岩油藏的气饱和度具有良好的潜力。将频率相关的AVA反演应用于叠前的地震数据表明,反P波频散属性与致密气砂岩产层区的天然气产量呈正相关。这项研究中进行的岩石物理建模方法和频率相关的AVA反演方法对于评价致密气砂岩油藏的气饱和度具有良好的潜力。
更新日期:2021-04-29
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