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A comparative analysis of time–depth relationships derived from scientific ocean drilling expeditions

Citation

Sauermilch, I and Mateo, ZRP and Boaga, J, A comparative analysis of time-depth relationships derived from scientific ocean drilling expeditions, Marine Geophysical Research, 40, (4) pp. 635-641. ISSN 0025-3235 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 Springer Nature B.V.

DOI: doi:10.1007/s11001-019-09393-7

Abstract

Time–depth relationships (TDR) are required for correlating geological information from drill sites with seismic reflection profiles. Conventional time–depth domain conversion is implemented using P-wave velocity data, derived from downhole sonic logs, calibrated with vertical seismic check-shots. During scientific ocean drilling expeditions, immediate seismic correlation is carried out using laboratory velocities measured on recovered core material. As these three velocity measurements vary significantly in signal frequency, resolution and acoustic pathways, they carry potential for substantial TDR differences and consequent miscorrelation to seismic profiles. Our analytical work uses the comprehensive scientific ocean drilling dataset to quantify these differences in core-seismic integration. TDRs are calculated and compared at sites where check-shot, sonic log, and laboratory velocity measurements cover the same depth segments of the drill hole. We find that the maximum differences between the TDRs (TDR diffmax ) reach up to 55%, which can cause fundamental errors in the seismic correlation. No direct relationship to porosity and bulk density of the cored material is observed. Instead, higher TDR variability is found at sites with carbonate content > 70%, particularly with coarser grain texture. Sites containing primarily igneous and siliciclastic sequences show less than 10% TDR diffmax . This semi-quantitative criterion indicates that downhole logging should be conducted during drilling expeditions, especially at sites with carbonate sequences, or low core recovery, to ensure accurate core-seismic integrations.

Item Details

Item Type:Refereed Article
Keywords:time–depth relationship, scientific ocean drilling, P-wave velocity measurement, seismic check-shot, downhole sonic log
Research Division:Earth Sciences
Research Group:Geophysics
Research Field:Seismology and seismic exploration
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Sauermilch, I (Miss Isabel Sauermilch)
ID Code:137267
Year Published:2019
Web of Science® Times Cited:1
Deposited By:Oceans and Cryosphere
Deposited On:2020-02-06
Last Modified:2020-08-12
Downloads:0

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