Regional depth-conversion of mapped seismic two-way-times in the Cooper-Eromanga Basins

Hillis, Richard R.; Macklin, T.A.; Siffleet, P.

doi:10.1071/eg995412

Cited by 8 publications

(4 citation statements)

References 2 publications

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“…Maps of raw interval velocities are also often unreliable for predicting velocities at undrilled locations because of relatively rapid spatial changes in exhumation which cause rapid velocity variations. Hillis et al (1995), in a study of depth-conversion of the Cooper-Eromanga basins, showed that the velocity anomaly method is significantly more accurate than the interval velocity method. Hillis et al's (1995) study covered only a portion of the South Australia sector of the Cooper-Eromanga basins.…”

Section: Influence Of Exhumation On Velocity/depth Conversionmentioning

confidence: 97%

Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration

Mavromatidis¹,

Hillis

2005

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Exhumation in the Eromanga Basin of South Australia and Queensland has been quantified using compaction methodology. All methods of estimating exhumation utilize rock properties that are affected by, and retain a memory of, burial in excess of that presently observed. The tool used for estimating the exhumation in this study is analysis of the degree of overcompaction of rock units. Since porosity describes compaction state, the sonic log, controlled strongly by the amount of porosity, is an appropriate indicator of compaction and, hence, is used for quantifying exhumation from compaction. The standard method of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified, and seven units, predominantly shales ranging in age from the Cretaceous to the Jurassic, have been analysed. All units yield similar results. Burial at depth greater than currently observed is the most likely cause of overcompaction since it is unlikely that sedimentological and/or diagenetic processes are responsible for similar amounts of overcompaction in different lithologies. The results of the compaction analysis reveal that Late Cretaceous-Tertiary exhumation increases eastwards from the Patchawarra Trough, through the Gidgealpa-MerrimeliaInnamincka Trend and Nappamerri Trough into the Queensland sector of the basins. This study has major implications for hydrocarbon exploration. Predicted maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. The exhumation study helps to quantify velocity anomalies associated with overcompaction. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets.

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Section: Influence Of Exhumation On Velocity/depth Conversionmentioning

confidence: 97%

Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration

Mavromatidis¹,

Hillis

2005

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“…This loop ran over the four time‐to‐depth conversion methods with increasing well control for each additional loop. This method is known as cross‐validation, or blind well‐testing, where the initial loop uses three well control points during time‐to‐depth conversion to predict the fourth well, then the second loop uses four wells to predict the fifth well and so forth ( n wells to predict the n th + 1 well) (Devijver and Kittler ; Hillis, Macklin and Siffleet ; Kohavi ). The error is calculated for each time‐to‐depth conversion for each loop and is measured by comparing the predicted grid depth with the known well depth at the n th + 1 well location.…”

Section: Methodsmentioning

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

Kulikowski

Hochwald²,

Amrouch

2018

Geophysical Prospecting

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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.

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“…For multilayer time–depth conversion, the travel path of the seismic wave through overlying layers needs to be considered; therefore a layer‐cake depth conversion was completed. To estimate interval velocities required for depth conversion of each layer in two‐way travel time, ‘instantaneous’ velocities from sonic logs were integrated to give linear and power law approximations for the velocity variation with depth (Hillis et al ., 1995; Al‐Chalabi, 1997). Power law functions were applied to the oldest formations as they better reflect the change in the velocity rates with depth due to compaction (e.g.…”

Section: Seismic Reflection Profilesmentioning

confidence: 99%

Timing and mechanisms controlling evaporite diapirism on Ellef Ringnes Island, Canadian Arctic Archipelago

et al. 2010

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The Permo -Carboniferous to Eocene Sverdrup Basin in Canada's Arctic Archipelago is strongly in£uenced by evaporite diapirism. However, salt structures within the basin have not been extensively investigated recently due to their remote location.This study includes the interpretation of legacy seismic re£ection and borehole data to characterize the geometry of selected evaporite domes, and1D backstripping of wells to investigate tectonic and sedimentary in£uences on diapirism. Extensional rift-structures appear to have played a signi¢cant role in the formation of evaporite domes by triggering and directing salt movement. Diapirism was initiated by at least the MiddleTriassic and continued to develop during the Mesozoic. Di¡erential loading of salt on opposing east^west dome margins led to their present day asymmetric geometries. Diapir growth rates in the Mesozoic were closely linked to the rate of sedimentation and in£uenced by regional tectonism.

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Regional depth-conversion of mapped seismic two-way-times in the Cooper-Eromanga Basins

Cited by 8 publications

References 2 publications

Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration

Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration

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

Timing and mechanisms controlling evaporite diapirism on Ellef Ringnes Island, Canadian Arctic Archipelago

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