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https://hdl.handle.net/2440/84916
2024-03-28T17:01:05ZSpectral gamma ray characterisation of the Dongara Sandstone, Perth Basin, W.A.: applications to high-resolution correlation
https://hdl.handle.net/2440/121128
Title: Spectral gamma ray characterisation of the Dongara Sandstone, Perth Basin, W.A.: applications to high-resolution correlation
Author: Di Bacco, Mark Phillip
Abstract: The northern Perth Basin has been a proven hydrocarbon province since the 1960s, however, little is known about the internal stratigraphy of the primary reservoir target the late Permian Dongara Sandstone. Spectral gamma ray data has previously been used in the high - resolution correlation of sediments, but its potential in the Perth Basin has not been previously determined. The effectiveness of this technique is investigated here. Spectral gamma ray (SGR) data were acquired from cores of the Dongara Sandstone using a hand -held gamma ray spectrometer. These data were combined with the relatively sparse wireline log SGR data available for the Dongara Sandstone. A study of the ratios of K, Th and U concentrations was first undertaken to determine whether SGR analysis was applicable in high - resolution correlation in the Dongara Sandstone. Core data was proven to be adequately precise for the comparison with wireline SGR data. It was confirmed that rocktypes could be clearly differentiated from one another on the basis of their SGR signatures. It was also proven that intra- formational character of the Dongara Sandstone could be identified from the SGR signatures, and that this character may have application in high - resolution correlation. Once the effectiveness of the SGR data for correlation had been demonstrated, the data were analysed with a suite of petrophysical software, creating a series of SGR composite logs for each well. There was a good similarity between the SGR composite logs from rocks that had both wireline and core SGR measurements taken. This indicates that the core SGR can be confidently integrated with the wireline SGR data for use in interpretation. These SGR composite logs were used in high - resolution correlation of the Dongara Sandstone. Composite logs effectively display specific SGR signatures as a distinct colour, thus indicating the bulk mineralogy of the sediment and giving indications of distinct depositional facies. In particular, high- thorium intervals were interpreted as representative of beach facies due to the likely presence of the heavy mineral monazite. These facies were recognised in the composite logs, and in many cases, facies could be correlated between wells in neighbouring fields. The stratigraphic and lateral extents of these facies were defined, enabling the construction of palaeogeographic maps for three chronologically separate Late Permian sediment packages. From these maps, the paleogeographic evolution was inferred. These maps indicate that the Dongara Sandstone is interpreted as having deposited on a series of back - stepping shorelines, depositing during a sea level transgression. The sequential changes in facies distributions identified from SGR data can assist in defining the sequence stratigraphy of the Dongara Sandstone. With the internal architecture of the Dongara Sandstone defined, accurate predictions of reservoir distribution and quality can be made. This has important implications in the future exploration and exploitation of hydrocarbon accumulations within the Dongara Sandstone.2004-01-01T00:00:00ZGeomechanical modelling of stress magnitude and orientation across fault and its relation to hydraulic fracturing
https://hdl.handle.net/2440/119147
Title: Geomechanical modelling of stress magnitude and orientation across fault and its relation to hydraulic fracturing
Author: Karatela, Ehtesham
Abstract: With intense exploration around the world, easily extractable hydrocarbons are getting more and more difficult to find. Major conventional hydrocarbon accumulations have been targeted and are being produced; but increased world’s consumption has led petroleum exploration and production industry to consider exploiting targets that were not believed to be economical. Tight reservoirs include shale gas, shale oil, coal seam gas (CSG) and tight sands. This concept has changed the conventional view of shales from being source and seal rock to unconventional perception –as reservoir. These reservoirs have minimal porosity and permeability which is not sufficient to produce at economic rates. Developing these reserves may require hydraulic fracturing to create a predictable network of fractures with height of several hundred feet through which hydrocarbons can easily flow towards borehole. Even if these reservoirs are fracture stimulated at best of the knowledge and skills; production from two wells in the same field is never the same. For a successful fracturing treatment, it is necessary to understand impact of existing fractures, faults and stress regimes in the subsurface. Geologic structures influence the stress field locally and show deviation from the regional trend of stress pattern. This study utilizes geomechanical modeling with static elastic moduli to depict stress magnitude and orientation around faults. For the purpose, stress magnitudes estimated by Reynolds et al., (2006) are used. Strike-slip stress regime prevails in at the depth interval selected. A thorough study using different lithologies, σH azimuth and fault size is carried out. Stress concentrate at the fault tips on opposite quadrants of the fault tips. Fluctuation in stress magnitude increases with increase in fault size. However, the variation diminishes after fault size of 1500 meters. These models help in understanding the orientation of fractures during hydraulic fracturing and help to recognize stress barriers that may affect production from an unconventional reservoir.2012-01-01T00:00:00ZControls on porosity in the Pab Sandstone, Kirthar Basin, Pakistan
https://hdl.handle.net/2440/116312
Title: Controls on porosity in the Pab Sandstone, Kirthar Basin, Pakistan
Author: Enman, Travis
Description: 2 v. : ill., maps; Volume two consists of 21 folded enclosures; Pages 23, 47, 87 are missing from the print and digital copies of the thesis1996-01-01T00:00:00ZReservoir characterisation of the Jurassic Springbok Sandstone, Surat Basin, Queensland
https://hdl.handle.net/2440/114138
Title: Reservoir characterisation of the Jurassic Springbok Sandstone, Surat Basin, Queensland
Author: Gallagher, Victoria
Abstract: The Late Jurassic Springbok Sandstone unconformably overlies the mid-Jurassic Walloon
Subgroup in the northeastern region of the Surat Basin, Queensland. The Walloon Subgroup
contains significant economic coal seam gas (CSG) reserves which are currently under
significant development. Development of CSG for production requires the extraction of
significant volumes of water from the coal seams to enable the gas to flow. The dewatering
process has the potential to affect the Springbok Sandstone as it may be in hydraulic
connection with the coal seams. The aim of this study is to characterise the reservoir quality,
stratigraphic architecture and primary geologic controls on the Springbok Sandstone in order to
gain an understanding of the potential for hydraulic interaction with the underlying coal
measures. The depositional characteristics of the Springbok Sandstone were evaluated by
analysing wireline line logs and the cored intervals of wells, and the petrology and reservoir
quality of the lower section of the Springbok Sandstone was conducted through statistical
analysis of thin sections, XRD data and RCA data.
The Springbok Sandstone has been previously interpreted as a thick sequence of channel
sands interbedded with relatively minor quantities of heterolithic sandstone, siltstone, mudstone
and coal lithologies deposited in a vast intracratonic alluvial plain in warm temperate conditions.
Core and wireline log analyses indicate that the Springbok Sandstone typically consists of a
thin, low-permeability blocky basal sandstone and two major fining-upwards sequences, each
consisting of channel sands at the base that fine-up into overbank and mire environments. An
erosional unconformity exists at the base of the Springbok Sandstone and between each
intraformational unit. The basal sandstone has been heavily eroded in the west of the study
area by the later succession of channel sands. This lower section of the Springbok Sandstone
appears to have been deposited in a high-energy braided stream environment, while the upper
section of the Springbok Sandstone was deposited in a lower energy meandering stream
environment. lsopach maps suggest that paleoflow was towards the centre of the basin and that
there may have been syndepositional deformation of the basin during the Late Jurassic.
The geologic controls on the detrital composition and diagenesis of the Springbok Sandstone
are complex. Analysis of thin sections indicates that the sediment in the lower Springbok
Sandstone section is generally medium grained, well sorted and mineralogically immature
volcanogenic feldspathic litharenite to litharenite. The formation contains abundant well
preserved lithic clasts, feldspars and biotite. The small sample size and mixed sediment
composition of volcanic, plutonic and metamorphic fragments and post-depositional alteration
precluded conclusive petrographic provenance analysis. High clay contents are present in the
volcanic-rich sediments, predominantly including kaolin and highly smectitic mixed-layer illite
interlayers, indicating that the formation may be freshwater sensitive.
The reservoir quality of the lower section of the Springbok Sandstone is principally controlled by
depositional environments, detrital mineralogy, clay alteration and cementation, and ranges
from poor to excellent. These controls are highlighted by the relationship between lithofacies,
grain size, grain composition and diagenetic alteration. The highly heterogeneous cyclic nature
of the Springbok Sandstone has made correlation and prediction of reservoir properties difficult.
Reseruoir quality tends to increase as grain size increases and is best developed in medium to
coarse sandstones while lower energy depositional facies have substantially lower
permeabilities. The basal calcite cemented sandstones potentially represent a sealing lithology
however the unit is not laterally extensive across the study area. The areas with the highest risk
of reseruoir connectivity between the Springbok Sandstone and Walloons Subgroup were
identified where porous sands directly overlie the Walloon Subgroup, particulary in the west of
the study region.
Autocyclic processes were the primary driver for much of the local scale composition variation,
which was largely a function of hydrodynamic softing. Tectonic and climatic influence is also
evident in the stacking pattern of the Springbok Sandstone succession. Mechanical compaction
reduced the porosity and permeabilty of sandstones containing high labile grain content.
Cementation involved early stage glaucony, pyrite, chlorite and siderite mineralisation, followed
by later stage dissolution and kaolinisation of labile grains, illitisation of clays, fracture formation
and poikilotopic calcite mineralisation. Diagenetic processes have diminished the reseruoir
quality of the deeper sandstone samples. Reservoir quality tends to reduce with increased
burial, although moderate to high porosity and permeability are still observed at depth.
The results of this study highlight the heterogeneous nature of the Springbok Sandstone. The
formation comprises a series of heterogeneous sandstone and mudstone units with variable
reservoir quality. The stratigraphic and depositional trends identified in the stratigraphy,
sandstone composition and reservoir quality of the Springbok Sandstone can be used in future
predictive reservoir modelling.
Description: Front matter only available electronically. The complete thesis in print form is available from the University of Adelaide Library.2012-01-01T00:00:00Z