Jurassic to Lower Cretaceous tectonostratigraphy of the German Central Graben, southern North Sea

The Central Graben is a Mesozoic sedimentary basin that is significantly influenced by rift and salt tectonics. Its southern part is located in the German and Dutch sectors of the North Sea. Even though studies exist on the tectonic and stratigraphic development of the Danish and Dutch Central Graben, the German Central Graben as an important link is less investigated. We aim to fill this gap and to investigate the sedimentary development from the Latest Triassic to the Early Cretaceous, the relative influence of salt and rift tectonics on subsidence and how our results fit into the existing studies of the Danish and Dutch Central Graben. Knowledge of the development of the graben and its sedimentation is critical for any possible economic use like hydrocarbon exploitation or carbon capture and storage. Therefore, we mapped nine laterally traceable horizons on 2D and 3D reflection seismic data from the Lower Jurassic to the Lower Cretaceous within the German Central Graben and adjacent Danish Salt Dome Province as well as the northern Dutch Central Graben. These horizons include the base horizons of four tectonostratigraphic mega-sequences of the southern Central Graben adopted from the current Dutch tectonostratigraphic concept. Based on the mapping results, we constructed subsidence, thickness and erosion maps of the tectonostratigraphic mega-sequences and their subdivisions. The tectonostratigraphic mega-sequences were then correlated with well logs to determine the lithology. The results show that the structural and stratigraphic architecture of the German Central Graben was consecutively dominated by either subsidence controlled by rifting, salt tectonics or by thermal uplift and subsidence. We suggest that the German Central Graben is divided by a large strike-slip fault zone, the Mid Central Graben Transverse Zone, into a northern part that geologically rather belongs to the Danish and a southern part that rather belongs to the Dutch Central Graben. We discuss how this division and the tectonics influenced the regional lithology

Petroleum System Analysis of the Chalk Fields in the Danish and Dutch Sector of the Central Graben, North Sea

The purpose of this MSc thesis is to use seismic and well data to investigate and understand the petroleum system of the many hydrocarbon discoveries found within the chalk layers of the Danish and Dutch Central Graben. The conclusions from this petroleum system analysis are then used as a recipe to look for the remaining prospectivity within the area. Seismic interpretation together with seismic to well correlation and well calibration has been performed in order to create different kinds of maps before conducting a petroleum system analysis on the Cretaceous chalk play of the Danish and Dutch Central Graben. Key aspects of the remaining chalk prospectivity in these areas are then brought into consideration as a result of the things learned from the previous petroleum system analysis. Results showed that the discovered chalk fields in the Danish and Dutch Central Graben can be divided into five categories, based on their structural trapping characterization. The first three categories are found on top of salt structures in anticlinal four-way dip closures that are a result of halokinesis. The difference between them is based on how much the salt structure has pierced through the overlaying layers, ranging them as traps over salt domes with some degree of inversion overprint in category 1 to traps formed over heavily pierced salt diapirs in category 3. The category 2 is included in this selection based on the addition of a major fault that cuts the field in two. The fourth and fifth categories define fields that are either found within a structural closure created by an inversion-generated anticline or within a non-structural stratigraphic trap as a result of late structural tilting. The source rock for all these fields is identified as being the Upper Jurassic Bo Member that belongs to the Farsund Formation in the Danish Central Graben and as the Lower Jurassic Posidonia Shale Formation in the Dutch Central Graben. Hydrocarbon migrations from these rocks have occurred mostly vertical, by using the major faults and fractures that are created as a result of the syn- and post chalk structural events. Cases of lateral migration have also occurred through the low permeability nature of chalk, especially in the case of the stratigraphic trap. The four-way dip closures in category 1 to 4 act as one part of the trapping mechanism that controls the capture of the migrated hydrocarbons. A pinch out of the chalk layer against a ridge does this for the fifth category. The other part of the trap is constituted by the overlaying seal, which is represented by the Palaeocene Shale Formation. These shales have caused the chalk to become over-pressured, due to effectively closing off the Chalk Group hydrodynamically when rapid post-chalk deposition of the overburden rocks occurred. This has led to the maintaining of high porosities in the chalk and is one of the major effects of the success of the chalk play. Throughout the work, an increasing understanding of how important the syn- and post chalk depositional structural events are for the success of the chalk play has been obtained. By knowing when and in what kind of scale these events have occurred, are crucial in order to better determine if the essential elements and processes of the petroleum system are placed correctly in time and space for a prospect to be of economical value or not

Controls on the geometry, stratigraphic distribution and quality of coals of Middle to Upper Jurassic strata in eastern Australia

The Middle to Upper Jurassic Walloon Coal Measures of eastern Australia host petroleum resources mostly in the form of coal bed methane. The coals accumulated at a high-latitude (>75°S) during a greenhouse epoch and occur in regionally extensive fluviolacustrine successions. Previous studies have described the spatial relationship of facies using a variety of (and sometimes ambiguously defined) stratigraphic frameworks. This was complicated by the absence of marker beds or published radiometric dates. The coal beds are thin and laterally discontinuous and their origin, which has been poorly understood, has implications for consistent stratigraphic correlations. Improved correlation techniques and an understanding of the controls on coal bed geometry should allow better prediction of: 1) the location and architecture of prospective reservoirs, and 2) gas drainage patterns around individual wells. This study aims to address these questions by building upon pre-existing notions on the evolution of eastern Australia during the Middle to Late Jurassic using an integrated approach with new sedimentologic and palynologic data, combined with precise U-Pb dating of volcanic sediments and basin subsidence studies. Zircon from twenty-eight tuffs in 12 wells across the Surat and Clarence- Moreton Basins were dated using the high-precision chemical abrasion thermal ionization mass spectrometry (CA-TIMS) technique to within an error margin of ±40 ka. In addition, two volcanogenic sandstones from one well that intersected the Birkhead Formation in the Eromanga Basin were dated using the same methodology to within ±50 ka. On a 1237 km transect, five regional datums 75°S), the coals originated from peats that accumulated in mires that experienced a warm temperate climate. Rapid and frequent climate change in the polar region may have limited the window of opportunity for thick, widespread coals to develop. New sedimentological and palynological data from the Surat Basin substantially revises interpretations of the environments of deposition. Sedimentary facies and spore-pollen assemblages confirm deposition in a predominately fluviolacustrine setting. However, the identification of tidally-influenced facies, acritarchs and dinoflagellate cysts (a first for Jurassic-aged strata in the basin) indicate periods of brackish water conditions. Marine incursions may have come from the north and the east during time of high eustatic sea-level during the Jurassic. Palaeogeographic reconstructions over 13 Ma reveal extensive fluviolacustrine systems draining from an eroding orogenic belt into proximal estuarine complexes. Allocyclic controls revealed by incised valleys and the deposition of transgressive estuarine facies strongly suggests the accumulation of coal (peat) was unlikely to be coeval with clastic sedimentation because of frequent changes in base level. This study illustrates that a multidisciplinary approach (notably the acquisition of precise U-Pb dates from volcanic sediments and the recognition of subtle indicators of marine influences) can be used to elucidate complex continental successions over large geographic areas. These type of studies will help in the search for subtle oil and gas reservoirs and better calculation of resource and reserve numbers. They may also be of use in better understanding sedimentary mineral resources and groundwater aquifer systems.Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 201

Sustainable development for traditional inhabitants of the Torres Strait region : proceedings of the Torres Strait Baseline Study Conference, Kewarra Beach, Cairns, Queensland, 19-23 November 1990

In July 1989 the Prime Minister of Australia, the Rt. Hon. R.J.L. Hawke, MP,announced, as part of his statement on the environment, which was later published as Our County, Our Future, that the Australian Government would fund a four year environmental study of the Torres Strait marine environment. This study, the Torres Strait Baseline Study, was instigated in response to concerns expressed by Torres Strait Islanders, commercial fishermen and scientists, about possible effects on the marine environment of the Torres Strait from mining operations in the Fly River catchment area of Papua New Guinea

Middle Jurassic deltaic and coastal deposits in the Lulu-1 well of the Danish Central Trough

Four cores from the Middle Jurassic Bryne Formation of the Lulu-I well in the northernmost part of the Danish Central Trough have been investigated. The cores were slabbed and a detailed description and facies analysis carried out. The cored sequence is very heterogeneous and includes beds of sand-, silt-, claystone, and coal. Seven facies are defined and the sequence is interpreted as sediments of a deltaic interdistributary bay and associated environments overlain by sediments of a coastal environment.</jats:p

THE DRAINING OF THE MARSHLANDS OF EAST YORKSHIRE

PhDHolderness, the Vale of York, and the Vale of Pickering are three fairly typical marshland areas, and all three were originally wasteland. Medieval reclamation improved the siltlands of each area for arable and pasture, but the peatlands remained waterlogged for three-quarters of the year and were used mainly for summer pasture and as sources of fish, fowl and fuel, until the mid-eighteenth century. Between 176o and 1900 they were drained by the use of large-scale engineering methods. Improvements were greatest in Holderness, while in the other two areas much still remained to be done in the twentieth century. There are various reasons both for the similarities and differences in the drainage history of the three regions, and for the differences between these regions and the other marshland areas of England and Wales. Location, size, the existence or otherwise of a frontage on tidal water and the resulting existence of a 'Court of sewers.. -farming systems, patterns of ownership, navigation interests, and the influence of settlements, as well an the physical geography, am all shown to have had an influence both on the pace of improvement and on the pattern of drains developed. The present geography of the three areas shows clear traces of the earlier stages In their history

Energy recovery from spent mushroom compost and coal tailings.

Spent mushroom compost (SMC) is an agricultural waste disposed of in an unsustainable and environmentally degrading manner - mainly in landfills. For every 1 kg of mushrooms grown, approximately 5 kg of SMC is produced, where current generation in the UK is 200,000 tJa. Coal tailings, an industrial by-product from coal mining, are also discarded untenably in lagoons; removing these deposits will eliminate the associated environmental hazards. This project aimed to combine these waste materials into a suitable 'green' fuel for industry through thermal treatment, to produce energy from a sustainable source. Not only will this alleviate the issues regarding existing waste management strategies, but will also attempt to mitigate the environmental impacts of energy generation from nonrenewable sources, such as anthropogenic climate change, through the generation of renewable energy. This PhD research has shown that both materials had high moisture contents, which negatively impacted the calorific value (CV). Drying, though expensive, would thus be required prior to pelletisation and thermal treatment. Key pelletisation parameters were identified and manipulated to control product quality. Optimal values were experimentally-determined for pellet composition (50:50 wt% SMC:coal tailing ratio), moisture (10.5 %) and pressure (6000 psi/41 MPa); such pellets had a NCV of 16.11 MJ/kg. As these pellets were still friable, additional studies were carried out to further improve pellet quality, in tenns of density, tensile strength and durability. Elevated temperatures and steam were considered, in addition to the use of starch and caustic soda binders, which were all successful to varying degrees. Combustion, gasification and pyrolysis tests compared the raw SMC to SMC-coal tailing pellets, where pellet combustion performed better than the SMC alone, and fluidised-bed combustion was more efficient than the packed-bed. Although pyrolysis worked well, the CV of the fuel products were low, whereas gasification was unsuccessful. Consequently, in-depth studies into pellet combustion in a laboratory scale fluidised-bed were perfonned, examining: (i) combustionl fluidisation air flowrates (4.9-10.7 kg/hr); (ii) fuel pellet feedrates (2.02-4.58 kg/hr); and (iii) sand bed depths (0.22-0.30 m). The impacts on temperatures, combustion efficiency and gas concentrations, including acid gas species were analysed. The most favourable operating conditions resulted in high temperatures for efficient energy recovery, with minimal pollutants, although the addition of secondary air jets could further improve the already high combustion efficiencies. While gaseous pollutants are unlikely to be an issue, as the emissions produced generally conformed to the Waste Incineration Directive, efficient particulate collection will be required to remove flyash from the gas stream prior to release to the atmosphere. Industrial implications were explored for heat and power generation, where mass and energy balances for a theoretical furnace, boiler and turbine set-up were completed for various fuel throughputs. Excess heat from the process could be utilized to dry the initial materials, but the economic analysis showed this would be costly - totalling 7) of overall pelletisation expenses. Assuming an overall process efficiency of 18.6 %, a steam turbine could generate over 10 MWe, based on an SMC-coal tailing pellet feedrate of 400,000 tJa - to simulate a large, centralised energy-from-waste facility. FLUENT, a mathematical model, was able to effectively replicate the results of the experimentation and was then used to model particle elutriation and entrainment to assess the suitability of the transport disengagement height provided