{"title":"Pore pressure prediction based on rock physics theory and its application in seismic inversion","authors":"","doi":"10.1016/j.jappgeo.2024.105494","DOIUrl":null,"url":null,"abstract":"<div><p>Formation overpressure seriously affects drilling and downhole operation. Accurate prediction on the formation pore pressure can not only reduce the probability of drilling accidents, but also quantitatively evaluate the original formation pressure of underground pore space, which provides an important reference for site selection of carbon sink projects using underground space resources such as CO<sub>2</sub> geological storage. It is therefore necessary to set up a widely applicable method that is based on rock physics theory and conforms to the characteristics of rock mechanics and fluid mechanic. This method is suitable for both logging prediction and seismic inversion of pore pressure. The traditional method of predicting pore pressure based on P-wave velocity has multiple solutions, and the prediction based on S-wave velocity which is not sensitive to fluid has new significance. Based on the Hertz-Mindlin petrophysical model that considering pressure variation and the Gassmann fluid substitution equation that addresses the change in fluid saturation, this paper firstly derived rock physical formulas for predicting pore pressure in logging, and then derived the intrinsic power function relationship between the effective pressure (<em>P</em><sub><em>e</em></sub>) and S-wave velocity (<em>V</em><sub><em>s</em></sub>) as well as S-wave impedance (<em>I</em><sub><em>s</em></sub>). Based on this, a set of geophysical methods integrating S-wave velocity prediction, pore pressure prediction in well and seismic inversion is finally established. The efficacy of this method has been well validated, with an average error of 2.35% in S-wave velocities prediction, 4.5% in single-well pore pressure prediction. The results of seismic inversion of pore pressure are consistent with the phenomenon of overpressure development in actual working area. This method can be further extended to other areas, providing invaluable reference for underground operation such as oil and gas exploration and CO<sub>2</sub> geological storage.</p></div>","PeriodicalId":54882,"journal":{"name":"Journal of Applied Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Applied Geophysics","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0926985124002106","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Formation overpressure seriously affects drilling and downhole operation. Accurate prediction on the formation pore pressure can not only reduce the probability of drilling accidents, but also quantitatively evaluate the original formation pressure of underground pore space, which provides an important reference for site selection of carbon sink projects using underground space resources such as CO2 geological storage. It is therefore necessary to set up a widely applicable method that is based on rock physics theory and conforms to the characteristics of rock mechanics and fluid mechanic. This method is suitable for both logging prediction and seismic inversion of pore pressure. The traditional method of predicting pore pressure based on P-wave velocity has multiple solutions, and the prediction based on S-wave velocity which is not sensitive to fluid has new significance. Based on the Hertz-Mindlin petrophysical model that considering pressure variation and the Gassmann fluid substitution equation that addresses the change in fluid saturation, this paper firstly derived rock physical formulas for predicting pore pressure in logging, and then derived the intrinsic power function relationship between the effective pressure (Pe) and S-wave velocity (Vs) as well as S-wave impedance (Is). Based on this, a set of geophysical methods integrating S-wave velocity prediction, pore pressure prediction in well and seismic inversion is finally established. The efficacy of this method has been well validated, with an average error of 2.35% in S-wave velocities prediction, 4.5% in single-well pore pressure prediction. The results of seismic inversion of pore pressure are consistent with the phenomenon of overpressure development in actual working area. This method can be further extended to other areas, providing invaluable reference for underground operation such as oil and gas exploration and CO2 geological storage.
地层超压严重影响钻井和井下作业。准确预测地层孔隙压力,不仅可以降低钻井事故发生的概率,还可以定量评价地下孔隙空间的原始地层压力,为二氧化碳地质封存等利用地下空间资源的碳汇项目选址提供重要参考。因此,有必要建立一种以岩石物理理论为基础,符合岩石力学和流体力学特点,具有广泛适用性的方法。这种方法既适用于测井预测,也适用于孔隙压力的地震反演。传统的基于 P 波速度预测孔隙压力的方法存在多种解,而基于对流体不敏感的 S 波速度预测孔隙压力具有新的意义。本文以考虑压力变化的赫兹-明德林岩石物理模型和解决流体饱和度变化的加斯曼流体置换方程为基础,首先推导出测井中预测孔隙压力的岩石物理公式,然后推导出有效压力(Pe)与 S 波速度(Vs)以及 S 波阻抗(Is)之间的本征幂函数关系。在此基础上,最终建立了一套集 S 波速度预测、井中孔隙压力预测和地震反演于一体的地球物理方法。该方法的有效性得到了很好的验证,S 波速度预测的平均误差为 2.35%,单井孔隙压力预测的平均误差为 4.5%。地震反演孔隙压力的结果与实际工作区超压发展现象一致。该方法可进一步推广到其他领域,为油气勘探、二氧化碳地质封存等地下作业提供宝贵参考。
期刊介绍:
The Journal of Applied Geophysics with its key objective of responding to pertinent and timely needs, places particular emphasis on methodological developments and innovative applications of geophysical techniques for addressing environmental, engineering, and hydrological problems. Related topical research in exploration geophysics and in soil and rock physics is also covered by the Journal of Applied Geophysics.