Bulletin Article
In prospective basins affected by exhumation, uncertainty commonly exists regarding the maximum burial depths of source, reservoir, and seal horizons. One such basin is the Otway Basin, an important gas province in southeastern Australia, which has witnessed several exhumation events. Here, we present estimates of net exhumation magnitudes for 110 onshore and offshore petroleum wells based on the sonic transit time analyses of Lower Cretaceous fluvial shales. Our results show significant post-Albian net exhumation in the eastern onshore Otway Basin (1500 m [4920 ft]) and a generally minor net exhumation (200 m [655 ft]) elsewhere in the Otway Basin, consistent with estimates based on thermal history data. The distribution of net exhumation magnitudes in relation to mid-Cretaceous and Neogene compressional structures indicates that exhumation was dominantly controlled by short-wavelength basin inversion driven by plate-boundary forces.
Deeper burial coupled with high geothermal gradients in the onshore eastern Otway Basin and along the northern basin margin during the early Cretaceous have rendered Lower Cretaceous source rocks mostly overmature, with any remaining hydrocarbons from the initial charge likely to be trapped in tightly compacted reservoirs and/or secondary (fracture-related) porosity. However, the embrittlement of these reservoirs during their deeper burial may present opportunities for the development of low-permeability plays through hydraulic fracturing where smectite clay minerals are illitized. Source rocks at near-maximum burial at present day are at temperatures suitable for gas generation, with key controls on prospectivity in these areas including the sealing potential of faulted traps and the relationship between charge and trap development.
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American Association of Petroleum Geologists (AAPG)
Added on 31 December, 2013
Explorer Emphasis Article
By Louise Durham
It’s now been shown that the “sweet” aspect of an identified sweet spot can change – not only stratigraphically, but also laterally within the zone itself.
American Association of Petroleum Geologists (AAPG)
Added on 01 December, 2013
Explorer Article
By Sarah Haviland
Edinburgh, Scotland, has a new research center planning to open its doors in 2015. It is the Sir Charles Lyell Centre, named after Britain's 19th century geologist. The uptick of interest in emerging industries of shale oil and gas and deep sea metal mining is just one of the areas of the focus planned for the centre.
American Association of Petroleum Geologists (AAPG)
Added on 01 December, 2013
Explorer Article
By David Brown
The popularity of Don Clarke's talk on induced seismicity took him by surprise. Then, he was asked to give it as an ethics talk leading to him serving as the Distinguished Ethics Lecturer this year.
American Association of Petroleum Geologists (AAPG)
Added on 01 December, 2013
Bulletin Article
The Marcellus Shale is considered to be the largest unconventional shale-gas resource in the United States. Two critical factors for unconventional shale reservoirs are the response of a unit to hydraulic fracture stimulation and gas content. The fracture attributes reflect the geomechanical properties of the rocks, which are partly related to rock mineralogy. The natural gas content of a shale reservoir rock is strongly linked to organic matter content, measured by total organic carbon (TOC). A mudstone lithofacies is a vertically and laterally continuous zone with similar mineral composition, rock geomechanical properties, and TOC content. Core, log, and seismic data were used to build a three-dimensional (3-D) mudrock lithofacies model from core to wells and, finally, to regional scale. An artificial neural network was used for lithofacies prediction. Eight petrophysical parameters derived from conventional logs were determined as critical inputs. Advanced logs, such as pulsed neutron spectroscopy, with log-determined mineral composition and TOC data were used to improve and confirm the quantitative relationship between conventional logs and lithofacies. Sequential indicator simulation performed well for 3-D modeling of Marcellus Shale lithofacies. The interplay of dilution by terrigenous detritus, organic matter productivity, and organic matter preservation and decomposition affected the distribution of Marcellus Shale lithofacies distribution, which may be attributed to water depth and the distance to shoreline. The trend of normalized average gas production rate from horizontal wells supported our approach to modeling Marcellus Shale lithofacies. The proposed 3-D modeling approach may be helpful for optimizing the design of horizontal well trajectories and hydraulic fracture stimulation strategies.
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American Association of Petroleum Geologists (AAPG)
Added on 30 November, 2013
Explorer Division Column EMD
By Jeremy Boak
A recent story about Shell’s withdrawal from a long-lived project on in situ production of shale oil from oil shale was an interesting example of over-interpretation of a small dataset.
American Association of Petroleum Geologists (AAPG)
Added on 01 November, 2013
Explorer Regions and Sections
By Carol McGowen,Joe Curiale,Michael Abrams,Ross Clark
Concepts and technologies developed for liquid-rich unconventional plays in North America are on the verge of being exported worldwide.
American Association of Petroleum Geologists (AAPG)
Added on 01 October, 2013
Explorer Policy Watch
By Edith Allison
As shale gas development has boomed over the past decade and public concern about its safety has swelled, both regulatory agencies and operating companies have accelerated their efforts to improve environmental safety.
American Association of Petroleum Geologists (AAPG)
Added on 01 October, 2013
Explorer Emphasis Article
By Louise Durham
A valuable study funded by the Texas Water Development Board sets aside the controversy and takes a closer look at hydraulic fracturing and water resources and consumption.
American Association of Petroleum Geologists (AAPG)
Added on 01 October, 2013
Explorer Policy Watch
By Edith Allison
The president’s Climate Action Plan, released June 25, aims to slow the effects of climate change.
American Association of Petroleum Geologists (AAPG)
Added on 01 September, 2013