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Volume 38 Number 9
  • ISSN: 0263-5046
  • E-ISSN: 1365-2397

Abstract

Abstract

Models to calculate pore pressure from the resistivity log have been developed in the Gulf of Mexico since the 1960s. The same approach has been difficult in the North Sea. Eight hundred released Norwegian exploration wells have been studied in detail. The statistical relationship between the following five logs; the sonic, density, neutron, gamma ray and resistivity log evaluated on 98 selected exploration wells. The statistical method chosen is the Principal Component Analysis. It suggests that the resistivity response is more or less random compared to the typical porosity logs; density, neutron and sonic. This suggests that no porosity or compaction information can be extracted from the resistivity log in the North Sea, Norwegian Sea or the Barents Sea. The resistivity log should therefore not be used to calculate porosity or predict or calculate pore pressure offshore Norway, UK, Denmark or Holland.

It has been suggested that the main case for the random resitivity (salinity) could be fresh water input from the glacial ice cover during the Quaternary period. But there are also studies that suggest there must be a meteoric water influx that is much older than Quaternary. Influx is not from the surface and down, but either lateral or from deeper down in the strata.

This suggests that detailed resistivity analysis must be done prior to interpreting CSEM data. So, far CSEM data acquired in the North Sea have given questionable results.

EAGE Publications BV
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/content/journals/10.3997/1365-2397.fb2020066
2020-09-01
2024-04-19

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Why the resistivity log should not be used to calculate or predict pore pressure in the North Sea
First Break 38, 57 (2020); https://doi.org/10.3997/1365-2397.fb2020066
/content/journals/10.3997/1365-2397.fb2020066
/content/journals/10.3997/1365-2397.fb2020066
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  • Article Type: Research Article

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