Viscous remanent magnetization: a tool for orientation of drill cores

Rolph, Tim; Shaw, John; Harper, T.R.; Hagan, J. T.

doi:10.1144/gsl.sp.1995.098.01.14

Cited by 12 publications

(9 citation statements)

References 1 publication

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“…Secondly, additional diametral sawcuts could be made on the two halves of the initial core, monitoring strains using the strain rosettes attached at the end of each core piece remaining from the initial sawcut. This technique, known as laboratory inherent force evolution (LIFE), was combined with a demagnetization process for core orientation (Rolph et al 1995) and shown to be consistent with stress determinations made using the ASR procedure and interpretations based on wellbore breakout (Fig. 3, Table 1).…”

Section: History and Objectivesmentioning

confidence: 57%

The nature of stress state: numerical and laboratory experiments and some field observations

Harper¹,

Hagan²

2015

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Simulations of the stress state in a region of discontinuously fractured rock revealed a strongly heterogeneous, self-organized stress distribution displaying internally balanced strains and corresponding energy storage. The explicit simulations follow a sequence which may be inferred to be irreversible and strongly dependent on interaction between fractures, implying a time-dependency. The state of the simulated reservoir displays a sensitivity characteristic of marginal stability. These numerical observations are compared with new and previous laboratory and field experiments spanning a wide range of size, stress magnitude and stress difference. The characteristics of the state of the simulated reservoir, laboratory samples and field behaviour are found to be consistent with the numerical predictions. A stress memory is evident. This supports previous conclusions that the concept of stress state as uniform, constant and resulting from averaged values of stresses or displacements, presently applied at remote and artificial boundaries, is grossly oversimplified and flawed.

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Section: History and Objectivesmentioning

confidence: 57%

The nature of stress state: numerical and laboratory experiments and some field observations

Harper¹,

Hagan²

2015

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“…The accuracy of this method depends upon the number of gauges and sawcuts (redundancy of data), level of viscous remanent magnetisation in the core (Rolph, Shaw, Harper, & Hagan, 1995) which primarily determines the accuracy of core orientation, the diameter of the core and number of gauges used. As a direct result of the weakness and heterogeneity (induced by tectonic mixing) of the core, which reduced the potential core samples to a small number, the tested sample was only 38 mm in diameter and was only strain-gauged at the one end which was free of fractures.…”

Section: Determination Of the Azimuth Of Maximum Horizontal Stress Frmentioning

confidence: 99%

Stress state and its influence on drilling performance in the Brighton Marine field, Trinidad

Harper

Chambers²

2004

Marine and Petroleum Geology

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“…One core (DB) is unoriented and the other (EC) is oriented. In studies of unoriented cores, the viscous remanent magnetization (VRM) has been utilized in an attempt to orient the core (e.g., Van der Voo and Watts, 1978;Rolphe et al, 1995;Dennie et al, 2012). We evaluate this method to orient the DB core and compare the results to the oriented EC core.…”

Section: Introductionmentioning

confidence: 99%

Remagnetization of Marcellus Formation in the Plateau Province of the Appalachian Basin

et al. 2019

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An integrated paleomagnetic, magnetic fabric, and petrographic study of two cores (EC, oriented; DB, unoriented) in the Devonian Marcellus Formation from the Plateau Province (PA) indicates the presence of chemical remanent magnetizations (CRMs) and extensive diagenetic alteration. Anisotropy of magnetic susceptibility results indicate a predominately oblate fabric. Some specimens contain a prolate fabric that is interpreted as diagenetically altered. A well-developed viscous magnetization, possibly contaminated by a drilling induced component, is not present in either core, and cannot be used for orientation. An intermediate temperature component (ITN) with steep down inclinations is removed in both cores below ∼300 • C. Specimens in DB also contain a component with steep up inclinations (ITR) that is removed between 300 and 440 • C. The ITN is interpreted to reside in magnetite and/or possibly pyrrhotite, and the ITR resides in magnetite. The ITN could be a reversal of ITR, acquired in the Cretaceous to Cenozoic based on a comparison with the expected inclinations. Alternatively, the ITN could be a contaminated by a Brunhes viscous magnetization. Specimens from both cores contain a characteristic remanent magnetization (ChRM) with shallow inclinations that is removed by 500 • C in DB and 460 • C in EC, and is interpreted to reside in magnetite. The DB ChRM has an inclination of −9.0 • , which corresponds to a range of ages between 310 and 225 Ma based on the expected inclinations. The ChRM in EC has streaked declinations, which may have been caused by core barrel rotation. Shallow inclinations (−3.7 • ) in this core suggest a range of acquisition from 305 to 230 Ma. Rock magnetic data are consistent with the presence of magnetite but provide conflicting evidence for pyrrhotite. The ChRM in DB is interpreted as a CRM whereas the ChRM in EC could be thermoviscous in origin. Diagenetic studies indicate a complex paragenesis with authigenic minerals such as barite, sphalerite, baroque dolomite, and sylvite suggestive of alteration by external fluids. The presence of the CRM in highly altered zones suggests it is related to alteration by external fluids, although its presence in other facies suggests that burial diagenetic processes could also be a cause of remagnetization.

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Viscous remanent magnetization: a tool for orientation of drill cores

Cited by 12 publications

References 1 publication

The nature of stress state: numerical and laboratory experiments and some field observations

The nature of stress state: numerical and laboratory experiments and some field observations

Stress state and its influence on drilling performance in the Brighton Marine field, Trinidad

Remagnetization of Marcellus Formation in the Plateau Province of the Appalachian Basin

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