The Spontaneous Ray Log

A New Aid for Constructing Pseudo-Synthetic Seismograms

Adnan Quadir, Charles Lewis, Ruey-Juin Rau

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Conventional synthetic seismograms for hydrocarbon exploration combine the sonic and density logs, whereas pseudo-synthetic seismograms are constructed with a density log plus a resistivity, neutron, gamma ray, or rarely a spontaneous potential log. Herein, we introduce a new technique for constructing a pseudo-synthetic seismogram by combining the gamma ray (GR) and self-potential (SP) logs to produce the spontaneous ray (SR) log. Three wells, each of which consisted of more than 1000 m of carbonates, sandstones, and shales, were investigated; each well was divided into 12 Groups based on formation tops, and the Pearson product–moment correlation coefficient (PCC) was calculated for each “Group” from each of the GR, SP, and SR logs. The highest PCC-valued log curves for each Group were then combined to produce a single log whose values were cross-plotted against the reference well’s sonic ITT values to determine a linear transform for producing a pseudo-sonic (PS) log and, ultimately, a pseudo-synthetic seismogram. The range for the Nash–Sutcliffe efficiency (NSE) acceptable value for the pseudo-sonic logs of three wells was 78–83%. This technique was tested on three wells, one of which was used as a blind test well, with satisfactory results. The PCC value between the composite PS (SR) log with low-density correction and the conventional sonic (CS) log was 86%. Because of the common occurrence of spontaneous potential and gamma ray logs in many of the hydrocarbon basins of the world, this inexpensive and straightforward technique could hold significant promise in areas that are in need of alternate ways to create pseudo-synthetic seismograms for seismic reflection interpretation.

Original languageEnglish
Pages (from-to)2093-2120
Number of pages28
JournalPure and Applied Geophysics
Volume175
Issue number6
DOIs
Publication statusPublished - 2018 Jun 1

Fingerprint

synthetic seismogram
seismograms
Gamma rays
aid
rays
well
correlation coefficients
gamma rays
Hydrocarbons
self potential
hydrocarbons
Carbonates
Sandstone
shales
hydrocarbon exploration
sandstones
Neutrons
seismic reflection
electrical resistivity
carbonates

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

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abstract = "Conventional synthetic seismograms for hydrocarbon exploration combine the sonic and density logs, whereas pseudo-synthetic seismograms are constructed with a density log plus a resistivity, neutron, gamma ray, or rarely a spontaneous potential log. Herein, we introduce a new technique for constructing a pseudo-synthetic seismogram by combining the gamma ray (GR) and self-potential (SP) logs to produce the spontaneous ray (SR) log. Three wells, each of which consisted of more than 1000 m of carbonates, sandstones, and shales, were investigated; each well was divided into 12 Groups based on formation tops, and the Pearson product–moment correlation coefficient (PCC) was calculated for each “Group” from each of the GR, SP, and SR logs. The highest PCC-valued log curves for each Group were then combined to produce a single log whose values were cross-plotted against the reference well’s sonic ITT values to determine a linear transform for producing a pseudo-sonic (PS) log and, ultimately, a pseudo-synthetic seismogram. The range for the Nash–Sutcliffe efficiency (NSE) acceptable value for the pseudo-sonic logs of three wells was 78–83{\%}. This technique was tested on three wells, one of which was used as a blind test well, with satisfactory results. The PCC value between the composite PS (SR) log with low-density correction and the conventional sonic (CS) log was 86{\%}. Because of the common occurrence of spontaneous potential and gamma ray logs in many of the hydrocarbon basins of the world, this inexpensive and straightforward technique could hold significant promise in areas that are in need of alternate ways to create pseudo-synthetic seismograms for seismic reflection interpretation.",
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The Spontaneous Ray Log : A New Aid for Constructing Pseudo-Synthetic Seismograms. / Quadir, Adnan; Lewis, Charles; Rau, Ruey-Juin.

In: Pure and Applied Geophysics, Vol. 175, No. 6, 01.06.2018, p. 2093-2120.

Research output: Contribution to journalArticle

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