Identification of Strike-Slip Faults Provides Insights into the Further Development of Mature Cooper Basin Fields

Geophysical Prospecting

Cooke

et al. 2017

A thorough and complete understanding of the structural geology and evolution of the Cooper‐Eromanga Basin has been hampered by low‐resolution seismic data that becomes particularly difficult to interpret below the thick Permian coal measures. As a result, researchers are tentative to interpret the basement fault architecture within the basin, which is largely undefined. To provide a better understanding of the basement fault geometry, all available two‐dimensional seismic lines together with 12 three‐dimensional seismic surveys were structurally interpreted with assistance from seismic attribute analysis. The Upper Cretaceous Cadna‐owie Formation and top Permian reflectors were analysed using a common seismic attribute technique (incoherency) that was used to infer the presence of faults that may have otherwise been overlooked. Detailed basement fault maps for each seismic survey were constructed and used in conjunction with two‐dimensional seismic data interpretation to produce a regional basement fault map. Large north‐northeast–south‐southwest‐striking sinistral strike–slip faults were identified within the Patchawarra Trough appearing to splay from the main northeast–southwest‐striking ridge. These sinistral north‐northeast–south‐southwest‐striking faults, together with field‐scale southeast–northwest‐striking dextral strike–slip faults, are optimally oriented to have potentially developed as a conjugated fault set under a south‐southeast–north‐northwest‐oriented strike–slip stress regime. Geomechanical modelling for a regionally extensive system of Cretaceous polygonal faults was performed to calculate the Leakage Factor and Dilation Tendency of individual faults. Faults that extend into Lower Cretaceous oil‐rich reservoirs with strikes of between 060°N and 140°N and a high to near‐vertical dip angle were identified to most likely be acting as conduits for the tertiary migration of hydrocarbons from known Lower Cretaceous hydrocarbon reservoirs into shallow Cretaceous sediments. This research provides valuable information on the regional basement fault architecture and a more detailed exploration target for the Cooper‐Eromanga Basin, which were previously not available in literature.

Section: Figure 20mentioning

confidence: 80%

Section: G E O L O G I C a L S E T T I N Gmentioning

confidence: 81%

Section: G E O L O G I C a L S E T T I N Gmentioning

confidence: 99%

mentioning

confidence: 99%

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Basement structural architecture and hydrocarbon conduit potential of polygonal faults in the Cooper‐Eromanga Basin, Australia

Geophysical Prospecting

Cooke

et al. 2017

“…In addition to these NE‐SW striking lineaments, SE‐NW strike‐slip faults are also present across the basin and can significantly complicate hydrocarbon production (Grant‐Wooley et al . ; Kulikowski, Amrouch and Cooke ; Kulikowski ).…”

Section: Geological Settingmentioning

confidence: 99%

An automated cross‐validation method to assess seismic time‐to‐depth conversion accuracy: a case study on the Cooper and Eromanga basins, Australia

Hochwald²,

Geophysical Prospecting

2018

Selecting a seismic time‐to‐depth conversion method can be a subjective choice that is made by geophysicists, and is particularly difficult if the accuracy of these methods is unknown. This study presents an automated statistical approach for assessing seismic time‐to‐depth conversion accuracy by integrating the cross‐validation method with four commonly used seismic time‐to‐depth conversion methods. To showcase this automated approach, we use a regional dataset from the Cooper and Eromanga basins, Australia, consisting of 13 three‐dimensional (3D) seismic surveys, 73 two‐way‐time surface grids and 729 wells. Approximately 10,000 error values (predicted depth vs. measured well depth) and associated variables were calculated. The average velocity method was the most accurate overall (7.6 m mean error); however, the most accurate method and the expected error changed by several metres depending on the combination and value of the most significant variables. Cluster analysis tested the significance of the associated variables to find that the seismic survey location (potentially related to local geology (i.e. sedimentology, structural geology, cementation, pore pressure, etc.), processing workflow, or seismic vintage), formation (potentially associated with reduced signal‐to‐noise with increasing depth or the changes in lithology), distance to the nearest well control, and the spatial location of the predicted well relative to the existing well data envelope had the largest impact on accuracy. Importantly, the effect of these significant variables on accuracy were found to be more important than choosing between the four methods, highlighting the importance of better understanding seismic time‐to‐depth conversions, which can be achieved by applying this automated cross‐validation method.

Combining geophysical data and calcite twin stress inversion to refine the tectonic history of subsurface and offshore provinces: A case study on the Cooper-Eromanga Basin, Australia

2017

Tectonics

The use of core samples, borehole image logs, and seismic data is common practice for obtaining valuable structural data; however, these data are often obtained in isolation from other methods and not usually used for paleostress inversion processes. Therefore, for the first time, we present a new approach for constraining paleoprincipal stress orientations and regimes by integrating geophysical data (seismic and well data) with calcite twin principal stress orientation inversion analysis to refine the evolution of entirely subsurface or offshore basins; a case study on the subsurface Cooper‐Eromanga Basin, Australia. Calcite samples were collected from oriented core, natural fracture data collected from borehole image logs, and fault data interpreted from three‐dimensional seismic surveys. The analysis of microscale, mesoscale and macroscale data constrained the paleoprincipal stress orientations and regimes of six successive tectonic events: (1) NNW‐SSE oriented strike‐slip Carboniferous Alice Springs event; (2) SE‐NW oriented compressional Mid‐Permian event; (3) NE‐SW oriented strike‐slip Late Permian Daralingie event; (4) E‐W compressional Late Triassic Hunter‐Bowen event; (5) E‐W compressional Late Cretaceous event; and (6) N‐S compressional Paleogene event. This study shows the applicability of integrating geophysics with calcite twin stress inversion to decipher the tectonic evolution of entirely subsurface and offshore provinces.