Ultrasonic wave attenuation dependence on saturation in tight oil siltstones
Ultrasonic wave attenuation dependence on saturation in tight oil siltstones
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DOI：
10.1016/j.petrol.2019.04.099
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发表时间：
2019-08
影响因子：
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通讯作者：
J. Ba;R. Ma;J. Carcione;S. Picotti
中科院分区：
文献类型：
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作者：
J. Ba;R. Ma;J. Carcione;S. Picotti
用两种独立的估计方法测量了致密油粉砂岩、碳酸盐岩和致密砂岩中的超声纵波衰减。在原位条件下，气水部分饱和粉砂岩对饱和度的依赖性与其他岩石相比表现出不同的行为。实验中的粉砂岩在含气条件下表现出随含水饱和度增加衰减逐渐减小的特征，且全气饱和度的衰减大于全油饱和度和全水饱和度的衰减。然而，以前的理论和实验研究表明，气水饱和的碳酸盐岩和砂岩在高含水饱和度时具有最高的衰减，并且通常，液体饱和的岩石比气体饱和的岩石表现出更多的衰减。孔隙弹性理论表明，两个主要的损失机制（由于织物的非均质性和斑片状饱和度）有不同的频率为粉砂岩的峰值，导致衰减随含水饱和度逐渐减少，而这些机制重叠在超声波频率碳酸盐岩和砂岩，导致衰减峰值在高含水饱和度。预测的衰减对流体类型的依赖性与大多数样品的测量结果一致。对于致密油粉砂岩，虽然该模型不能解释油水饱和度的实验结果，但可以得出结论，对于气水饱和度，由组构非均匀性引起的喷流主导衰减，这与碳酸盐岩和砂岩不同。实验研究表明，致密油藏中衰减对饱和度的依赖性与组构结构有关。该理论描述了这些行为，可以潜在地改进在储层中检测和监测多相流体的实践。
Ultrasonic P-wave attenuation was measured in tight oil siltstones, carbonates and a tight sandstone with two independent estimation methods. The dependence on saturation in gas-water partially-saturated siltstones at in-situ conditions shows a different behavior compared to the other rocks. The siltstones in our experiments exhibit a behavior characterized by a gradual decrease of attenuation with increasing water saturation in the presence of gas, and full-gas saturation shows more attenuation than full-oil and full-water saturations. However, previous theoretical and experimental studies show that gas-water saturated carbonates and sandstones have the highest attenuation at high water saturations, and generally, a liquid-saturated rock shows more attenuation than a gas-saturated one. Poroelasticity theory shows that the two dominant loss mechanisms (due to fabric heterogeneity and patchy saturation) have peaks at different frequencies for siltstones, resulting in a gradual decrease of attenuation with water saturation, while these mechanisms overlap at ultrasonic frequencies for carbonates and sandstones, leading to an attenuation peak at high water saturations. The predicted attenuation dependence on fluid type agrees with the measurement for most samples. Regarding the tight oil siltstones, although the model fails to explain the experimental results for oil-water saturation, it can be concluded that for gas-water saturation the squirt flow caused by fabric heterogeneity dominates the attenuation, which differs from carbonates and sandstones. Experimental studies show that the attenuation dependence on saturation in tight oil reservoirs can be associated with fabric texture. The theory describes these behaviors, which can potentially improve the practices of detecting and monitoring multi-phase fluids in the reservoirs.