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Mount Isa, Australia

Hillis R.R.,Deep Exploration Technologies CRC | Holford S.P.,University of Adelaide | Green P.F.,Geotrack International | Dor A.G.,Statoil | And 5 more authors.
Geophysical Journal International | Year: 2013

While Davis et al. provide convincing evidence for dynamic support of modern topography in NW Scotland, we take issue with their claims that the spatial distribution of Cenozoic denudation correlates poorly with the pattern of upper crustal shortening, and that the magnitude of shortening is insufficient to cause the observed denudation. We disagree with Davis et al.'s map of denudation, which forms the basis of their claims, and believe that their conclusions seriously downplay the widely documented contribution of crustal shortening to Cenozoic denudation of many areas of the British Isles.© The Authors 2013. Source


Franca L.F.P.,CSIRO | Mostofi M.,Deep Exploration Technologies CRC | Mostofi M.,Curtin University Australia | Richard T.,Deep Exploration Technologies CRC | Richard T.,Epslog SA Rue Hocheporte 76
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

Impregnated diamond bit has emerged as one of the most commonly used types in the extraction of underground resources in hard and abrasive formations. Despite the success and its frequent use, the drilling performance of these bits is still quite volatile and inconsistent due to a lack of fundamental understanding of the mechanisms governing the bit/rock interface. Impregnated diamond bits are rotary drag bits, in which the cutters also called segments or crowns are comprised of sintered metal powder with diamonds (natural or synthetic) uniformly distributed throughout its volume. The diamonds, which are exposed at the bit surface, are responsible for cutting away rock while the matrix provides the necessary bonds to retain the diamonds during their cutting life. Focusing our attention to evaluate performance of impregnated diamond bit, it is absolutely essential to establish interface laws, and also to establish a distinction between "topologically-invariant" and "topologically-variant" responses. Initially, specific laboratory tests are conduced with single segments and a procedure to identify topologically-invariant cutting response proposed. Interface laws for a segment are then derived, assuming that the cutting response is composed of two independent processes, pure cutting process and frictional contact or rubbing; and the rubbing process is composed by losses generated at both contact surfaces: diamond wear flat areas and matrix bearing surface. Next, impregnated diamond bit responses are investigated and the interface laws obtained, using the same logic established for segments. Finally, the parameters of the model are identified through an extensive series of laboratory tests. © 2014. Source


Tassone D.R.,University of Adelaide | Holford S.P.,University of Adelaide | Stoker M.S.,British Geological Survey | Underhill J.R.,University of Edinburgh | And 2 more authors.
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

Increasing demand for hydrocarbons is driving exploration in poorly understood and geologically complex basins. These include basins affected by exhumation, where there is often uncertainty regarding the maximum burial depths of source, reservoir and seal horizons. This uncertainty can be reduced by quantifying exhumation magnitudes using techniques such as sonic velocity analysis, which can be used to determine the compaction state of sedimentary rocks. The Mesozoic-Cenozoic basins between the Faroe, Orkney and Shetland Islands along the NW European Margin are oil and gas provinces whose subsidence histories have been interrupted by several tectonic phases, including multiple Cretaceous rifting, Paleogene volcanism and Oligo-Miocene inversion. We have used sonic velocity data from 23 wells to estimate the magnitude and distribution of Cenozoic net exhumation recorded in over-compacted intra-formational shale units identified from gamma-ray logs within Maastrichtian marine shales. Our results indicate that the Maastrichtian marine shales are at, or near (i.e. within ≤100 m net exhumation) maximum burial in the northeast (i.e. More and Magnus basins) and increase towards the southwest (i.e. North Rona Basin and Rona High) where post-Maastrichtian net exhumation magnitudes of ∼300-960 m are estimated. Source


Tassone D.R.,University of Adelaide | Holford S.P.,University of Adelaide | Stoker M.S.,British Geological Survey | Green P.,Geotrack International | And 3 more authors.
Basin Research | Year: 2014

The Mesozoic-Cenozoic basins located between the Faroe, Orkney and Shetland Islands along the NE Atlantic Margin are actively explored oil and gas provinces whose subsidence histories are complicated by multiple tectonic factors, including magmatism, inversion and regional-scale uplift and tilting, that have resulted in spatially variable exhumation. These basins also exhibit nonburial related, transient Cenozoic heating anomalies that make thermal history interpretation and burial history reconstructions problematic. In this study, we have applied a compaction-based approach, which is less susceptible to distortions from transient heating, to provide new constraints on Cenozoic burial and exhumation magnitudes in the UK sector of the Faroe-Shetland region using sonic transit time data from Upper Cretaceous marine shales of the Shetland Group in 37 wells. As estimates of exhumation magnitude depend critically on the form of the normal sonic transit time-depth trend, a new marine shale baseline trend was firstly constructed from shales presently at maximum burial, consistent with other marine shale baseline trends of different ages from nearby basins. Our results indicate that Upper Cretaceous marine shales are presently at or near (i.e. within ≤100 m net exhumation) maximum burial depths in the Møre and Magnus basins in the northeast of the study area as well as in the deeper water Faroe-Shetland Basin (i.e. Flett and Foula sub-basins). However, Upper Cretaceous strata penetrated by wells in the southwest have been more deeply buried, with the difference between maximum burial depth and present-day values (net exhumation) increasing from ca. 200 to 350 m along the central and northeastern parts of the Rona High to ca. 400-1000 m for wells located in the West Shetland Basin, North Rona Basin and southwestern parts of the Rona High. Although the precise timing of exhumation is difficult to constrain due to the complex syn- to post-rift tectonostratigraphic history of vertical movements within the Faroe-Shetland region, our estimates of missing section, together with available thermal history constraints and seismic-stratigraphic evidence, implies that maximum burial and subsequent exhumation most likely occurred during an Oligocene to Mid-Miocene tectonic phase. This was probably in response to major post-breakup tectonic reshaping of this segment of the NE Atlantic Margin linked to a coeval and significant reorganization of the northern North Atlantic spreading system, suggesting that fluctuations in intraplate stress magnitude and orientation governed by the dynamics of plate-boundary forces exert a major control on the spatial and temporal variations in differential movements along complexly structured continental margin. © 2014 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists. Source


Tassone D.R.,University of Adelaide | Holford S.P.,University of Adelaide | Hillis R.R.,Deep Exploration Technologies CRC | Tuitt A.K.,University of Adelaide
Geological Society Special Publication | Year: 2012

Parts of the Australian continent, including the Otway Basin of the southern Australian margin, exhibit unusually high levels of neotectonic deformation for a so-called stable continental region. The onset of deformation in the Otway Basin is marked by a regional Miocene-Pliocene unconformity and inversion and exhumation of the Cretaceous-Cenozoic basin fill by up to c. 1 km. While it is generally agreed that this deformation is controlled by a mildly compressional intraplate stress field generated by the interaction of distant plate-boundary forces, it is less clear whether the present-day record of deformation manifested by seismicity is representative of the longer-term geological record of deformation. We present estimates of strain rates in the eastern Otway Basin since 10 Ma based on seismic moment release, geological observations, exhumation measurements and structural restorations. Our results demonstrate significant temporal variation in bulk crustal strain rates, from a peak of c. 2 × 1016 s1 in the Miocene-Pliocene to c. 1.09 × 1017 s1 at the present day, and indicate that the observed exhumation can be accounted for solely by crustal shortening. The Miocene-Pliocene peak in tectonic activity, along with the orthogonal alignment of inverted post-Miocene structures to measured and predicted maximum horizontal stress orientations, validates the notion that plate-boundary forces are capable of generating mild but appreciable deformation and uplift within continental interiors. © The Geological Society of London 2012. Source

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