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Velocity anisotropy and trend in Niger Delta, Nigeria
Journal of Petroleum Exploration and Production Technology ( IF 2.2 ) Pub Date : 2021-03-22 , DOI: 10.1007/s13202-021-01136-y
Emmanuel Aniwetalu , Emmanuel Anakwuba , Juliet Ilechukwu

In geophysical data interpretation, matching the vertical velocity direction from seismic data with borehole-derived velocities is a challenging task because seismic-derived velocities are faster than borehole recorded velocities. This geophysical phenomenon is caused by velocity anisotropy. In this study, we used an empirical approach to estimate the degree of velocity anisotropy in the study area. The results showed that the delta anisotropy in sandstone beds varies from − 2.5% to 7.2% while most of them concentrate between 3.2% and 6.1%. The epsilon ranges between -6.4% and 9.3% while many of them concentrate between 3.2% and 7.2%. The gamma varies from − 6.3% to 7.3% while most of them concentrate between 1.2% and 5%. At shale beds, delta anisotropy varies from − 11.2% to 11.1% but most of them concentrate between 4.3% and 10.5%. The epsilon varies from − 7.2% to 14.5% while most of them concentrate between 4.5% and 10.5%. The gamma varies from 6.4% to 8.2% while majority of them concentrate between 2% and 5.3%. The results indicate that the study area is weakly to moderately anisotropic with shale beds having higher anisotropy values than sandstone beds. This probably results from preferential alignment of clay mineral orientations which also affect in situ velocity propagation. Three distinct velocity gradients (low, moderate and very high) were identified in the study area. These velocities vary erratically but showed northeast–southwest increase in velocities. Thus, the need to derive correction factors for individual wells for improved exploration success.



中文翻译:

尼日利亚尼日尔三角洲的速度各向异性和趋势

在地球物理数据解释中,将地震数据的垂直速度方向与井眼测得的速度相匹配是一项艰巨的任务,因为地震井测得的速度要比井眼测得的速度快。这种地球物理现象是由速度各向异性引起的。在这项研究中,我们使用一种经验方法来估计研究区域中速度各向异性的程度。结果表明,砂岩层中的三角各向异性在-2.5%至7.2%之间变化,而其中大多数集中在3.2%至6.1%之间。ε范围在-6.4%至9.3%之间,而其中许多浓度在3.2%至7.2%之间。伽玛范围从− 6.3%到7.3%,而大多数伽玛集中在1.2%和5%之间。在页岩层,δ各向异性在− 11.2%至11.1%之间变化,但大多数集中在4.3%至10.5%之间。ε在-7.2%至14.5%之间变化,而大多数集中在4.5%至10.5%之间。伽玛值范围从6.4%到8.2%,而大多数伽玛值集中在2%和5.3%之间。结果表明,研究区是弱到中等各向异性的,页岩床的各向异性值比砂岩床的各向异性值高。这可能是由于粘土矿物取向的优先排列而造成的,这也影响了原位速度的传播。在研究区域中确定了三个不同的速度梯度(低,中和非常高)。这些速度变化不定,但显示出东北向西南的速度增加。因此,需要为单个井导出校正因子,以提高勘探成功率。2%,而大多数人集中在2%至5.3%之间。结果表明,研究区是弱到中等各向异性的,页岩层的各向异性值比砂岩层的各向异性值高。这可能是由于粘土矿物取向的优先排列而造成的,这也影响了原位速度的传播。在研究区域中确定了三个不同的速度梯度(低,中和非常高)。这些速度变化不定,但显示出东北向西南的速度增加。因此,需要为单个井导出校正因子,以提高勘探成功率。2%,而大多数人集中在2%至5.3%之间。结果表明,研究区是弱到中等各向异性的,页岩床的各向异性值比砂岩床的各向异性值高。这可能是由于粘土矿物取向的优先排列而造成的,这也影响了原位速度的传播。在研究区域中确定了三个不同的速度梯度(低,中和非常高)。这些速度变化不定,但显示出东北向西南的速度增加。因此,需要为单个井导出校正因子,以提高勘探成功率。这可能是由于粘土矿物取向的优先排列而造成的,这也影响了原位速度的传播。在研究区域中确定了三个不同的速度梯度(低,中和非常高)。这些速度变化不定,但显示出东北向西南的速度增加。因此,需要为单个井导出校正因子,以提高勘探成功率。这可能是由于粘土矿物取向的优先排列而造成的,这也影响了原位速度的传播。在研究区域中确定了三个不同的速度梯度(低,中和非常高)。这些速度变化不定,但显示出东北向西南的速度增加。因此,需要为单个井导出校正因子,以提高勘探成功率。

更新日期:2021-03-22
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