Aspects of core-log integration: an approach using high resolution images

Lofts, Jeremy; Bristow, J. F.

doi:10.1144/gsl.sp.1998.136.01.23

Cited by 10 publications

(8 citation statements)

References 9 publications

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“…The joint core and log integration is utilized to: (1) calibrate core and log data; (2) extract particularly subsurface physical information such as lithological boundaries and (3) predict the lithology at places where core recovery is incomplete (e.g. Lofts & Bristow 1998; Major et al 1998). Results of core‐log integration are discussed in the section of physical properties and log units.…”

Section: Data Acquisition and Methodology For Core‐log Integrationmentioning

confidence: 99%

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Yeh

Dong

et al. 2008

Geophysical Journal International

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S U M M A R YTaiwan Chelungpu-fault Drilling Project (TCDP) was initiated to understand the physical mechanisms involved in the large displacements of the 1999 Taiwan Chi-Chi earthquake. Continuous measurements of cores (including laboratory work) and a suite of geophysical downhole logs, including P-and S-wave sonic velocity, gamma ray, electrical resistivity, density, temperature, electrical borehole images and dipole-shear sonic imager, were acquired in Hole-A over the depth of 500-2003 m. Integrated studies of cores and logs facilitate qualitative and quantitative comparison of subsurface structures and physical properties of rocks. A total of 10 subunits were divided on the basis of geophysical characteristics. Generally, formation velocity and temperature increase with depth as a result of the overburden and thermal gradient, respectively. Gamma ray, resistivity, formation density, shear velocity anisotropy and density-derived porosity are primarily dependent on the lithology. Zones with changes of percentage of shear wave anisotropy and the fast shear polarization azimuth deduced from Dipole Shear-Imager (DSI) are associated with the appearance of fractures, steep bedding and shear zones. The fast shear wave azimuth is in good agreement with overall dip of the bedding (approximately 30 • towards SE) and maximum horizontal compressional direction, particularly in the Kueichulin Formation showing strong shear wave velocity anisotropy. Bedding-parallel fractures are prevalent within cores, whereas minor sets of high-angle, NNW-SSE trending with N-and S-dipping fractures are sporadically distributed. The fault zone at depth 1111 m (FZA1111) is the Chi-Chi earthquake slip zone and could be a fluid conduit after the earthquake. The drastic change in fast shear wave polarization direction across the underlying, non-active Sanyi thrust at depth 1710 m reflects changes in stratigraphy, physical properties and structural geometry.

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Section: Data Acquisition and Methodology For Core‐log Integrationmentioning

confidence: 99%

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Yeh

Dong

et al. 2008

Geophysical Journal International

View full text Add to dashboard Cite

show abstract

“…A joint core and log study is important to calibrate the log data, extract particular subsurface physical information, and predict lithology at places where core recovery is incomplete (Lofts and Bristow 1998;Major et al 1998).…”

Section: Core and Log Integrationmentioning

confidence: 99%

Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

Hung¹,

Wu²,

Yeh³

et al. 2007

Terr. Atmos. Ocean. Sci.

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: 1) a bedding-parallel thrust fault with a 30-degree dip; 2) the lowest resistivity; 3) low density, V p and V s ; 4) high V p /V s ratio and Poisson's ratio; 5) low energy and velocity anisotropy, and low permeability or fluid mobility within the homogeneous gouge zone; 6) increasing gas (CO 2 and CH 4 ) emissions; and 7) being rich in smectite within the primary slip zone.Formation physical properties hold consistent relationships with either depth or lithology. Anisotropy of shear-wave velocity shows that the dominant fast shear polarization direction is in good agreement with an overall azimuth of the maximum horizontal stress axis, particularly within the strong anisotropic Kueichulin Formation. A drastic change in orientation of fast shear polarization across the Sanyi thrust fault at a depth of 1710 m reflects changes in stratigraphy, physical properties and structural geometry.

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“…This contribution focuses on reconstructing the lithologies in the altered oceanic basement drilled at Hole 801C (Figure 1). Considering that only 47% of the section was recovered, it was deemed essential to integrate the core and log data [see for example, Brewer et al , 1998; Lofts and Bristow , 1998; Major et al , 1998; Bartetzko et al , 2001] to enable reconstruction of the entire drilled section and quantify the relative proportions of the different basement lithologies (massive basalt, pillow basalt, breccia, sediment, and hydrothermal material) that control the chemical budgets.…”

Section: Introductionmentioning

confidence: 99%

Determining the inputs to the Mariana Subduction Factory: Using core‐log integration to reconstruct basement lithology at ODP Hole 801C

Barr

Révillon

Brewer

et al. 2002

Geochem Geophys Geosyst

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[1] Calculating elemental mass balance across subduction zones enhances our understanding of global geochemical budgets and large-scale Earth processes. However, to accurately constrain the input flux, it is critical to know the lithological diversity and chemical characteristics of the downgoing oceanic plate. The west Pacific altered ocean crust that was drilled during Ocean Drilling Program (ODP) Leg 185 represents a significant component of the input to the Mariana Subduction Factory. The lithological sequence in Hole 801C consists of aphyric basalt, occurring as thick massive units, pillow units, and breccia units. The shallowest basalts are intercalated with sediments and two hydrothermal deposits. Core recovery was good for a basement hole (average 47%); however, over half the lithological section was unaccounted for. Downhole logging data provide a continuous record of physical, chemical, and structural properties of the rocks at the borehole wall, thus, when calibrated using available cored material, they can be used to reconstruct lithology in unrecovered intervals. Core-log integration results reveal a significant bias in core recovery, with infrequent retrieval of delicate breccia units and preferential recovery of more massive, competent, and less altered flow units. This is important because the breccia units are host to many of the key tracer elements used in mass balance calculations. The massive basalts exhibit high density, resistivity and velocity values and low porosity and gamma ray values. Formation MicroScanner (FMS) images of massive basalts are bright (reflecting their resistive nature) with a homogenous texture and regular fracture pattern. Breccia or pillow basalts are characterised by low resistivity, density and velocity, and high porosity and gamma ray values and unrecovered intervals displayed these same characteristics. The reconstructed log-based lithological sequence consists of thick massive flow units (27.4%), pillow units (33%), breccia units (31%), sediments (1.4%), and hydrothermal deposits (1.3%), with 5.9% unclassified due to unreliable tool response in intervals where hole conditions were poor. These findings have a significant bearing on the Subduction Factory recycling equation. The proportion of pillow basalts doubled and the amount of breccia increased six-fold from that reported using core description alone, demonstrating convincingly that core-log integration is essential to provide an accurate representation of the input flux. The log-based stratigraphy reconstructed for Hole 801C represents the first example of Jurassic fast-spread (160 km/m.y.) ocean crust and provides constraints on the relationships between crustal structure, age, alteration, and spreading rate.

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Aspects of core-log integration: an approach using high resolution images

Cited by 10 publications

References 9 publications

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Core-log integration studies in hole-A of Taiwan Chelungpu-fault Drilling Project

Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

Determining the inputs to the Mariana Subduction Factory: Using core‐log integration to reconstruct basement lithology at ODP Hole 801C

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