This dataset was derived from well tops, seismic sections and some open file industry interpretations, utilising Petrosys mapping software.
The release of the 2015 Pedirka Basin Mapping data is the culmination of a series of projects completed in...

This dataset was derived from well tops, seismic sections and some open file industry interpretations, utilising Petrosys mapping software.

The release of the 2015 Pedirka Basin Mapping data is the culmination of a series of projects completed in 1993, 1994, 2001, 2012 and 2013 by Department of State Development and former agencies.

Significant projects containing the latest and most extensive horizon mapping in the Pedirka Basin area include the following projects:
Eromanga 2001
Eromanga Aquifer Study 2012 (completed for DEWNR)
Pedirka Mapping 2013.

A combination of results from the Eromanga Mapping Project (2012) and the 2013 Pedirka Mapping Project now sees complete coverage of the Pedirka Basin for 5 horizons, namely, Top Cadna-owie (C), Base Eromanga (J), Top Permian, Top Purni and Top Crown Point. A Top Basement (Z) for the equivalent area is provided by the 2001 Eromanga Project.

Surveying issues have been previously identified particularly in the NT area with many lines poorly located. Further, much of the processed data for the NT is either not available or can't be loaded due to the limited navigation data. Processed seismic data was interpreted where possible and extensive use was made of data from the numerous drill holes (water, petroleum and mineral) in the area to enable control of the interpretation. This current "wells" dataset incorporates all available proofed and validated drill holes. Water well data was validated by DEWNR staff, however mineral well and petroleum well data was also validated where required (i.e. when the data clearly appeared anomalous).

A description of formations mapped in the subject area and/or contained in this project include the following horizons:


Cadna-owie Formation
The top 'C' horizon is picked in the middle of a significant seismic trough. It is a fairly consistent marker horizon and is considered a reliable pick. The Cadna-owie regional mapping was first completed in 1996 from interpreted seismic Two-way Time data (TWT) derived from oil industry maps and direct seismic interpretation. These digital time maps were cross correlated with a 'warping' digital field derived from petroleum well depths to create depth maps. This is basically the equivalent of applying a velocity field. Various updates and extensions were included in 2001 and 2009, derived from new drilling and seismic data. This current dataset was completed in 2012 and incorporates all available proofed drill holes. Water well data was validated by DEWNR, however mineral well and petroleum well data was only validated where required (ie: when the data clearly appeared anomalous). Geological outcrop data and limited new seismic data were also included. The limits of the mapped formation are defined as contiguous areas. Small patches of Cadna-owie outside the contiguous area are not included.


Base Eromanga Basin
The Base Eromanga is located at the first occurrence of either, the Triassic Peera Peera Formation, the Permian Purni Formation, the Permian Crown Point Formation or any crystalline basement rock.

Also referred to as the base of Jurassic sediments, this surface represents a mixture of Triassic, Permian and Basement surfaces. The 'Aquifer' is defined here by the extent of permeable water bearing sandstones of the Cadna-owie Formation, plus lower formation layers which are part of the same aquifer system. These include the Algebuckina and Hutton Sandstones as well as minor horizons which contact the major reservoirs in some locations. The 'Base Aquifer' is defined as areas where the above sandstone reservoir contacts non reservoir sediments or crystalline rock. These non-reservoir layers are generally at the level of the Triassic, Permian or earlier sedimentary rock, or 'Basement' crystalline or metamorphic layers.


Peera Peera Formation
The Peera Peera formation is a fluvial sedimentary sequence deposited during the Triassic. Seismically it appears as a weak peak, fairly correlatable to its limits. The mapping came from isopaching the horizon from well picks, with the edges derived from seismic. This isopach was added to the Top Permian grid to derive the top Peera Peera/Base Eromanga map.

Top Permian Sediments (P)
The top Permian sediments are those Permian formations below the Eromanga basin. They are either the Purni Formation or the Crown Point Formation. 
Seismically the Permian top generally falls on weak seismic peaks and is reasonably easy to correlate. Seismic coverage was sparse.
Primary interpretation was from available digitized paper sections in 1999. Two way Time (TWT) digital data was cross correlated with a digital "warping field" derived from petroleum well depths to create a depth map. This is the equivalent to applying a velocity field.
A major update was completed in 2012 with the inclusion of all water bore, mineral hole, petroleum well and sub crop data. Limited, recent seismic data from the Northern territory was incorporated where possible but poor ties exist to existing data due to limited digital data.
In 2015, recent bore hole data allowed further refinement of the map data to be made.

Top Purni Sediments (PU)
The Purni Formation is a lacustrine, meandering fluvial and back swamp sedimentary unit from the early Permian. The top Purni Formation pick generally falls on a weak seismic peak and fairly correlatable.
This is the first Permian sedimentary layer below the Eromanga Basin but is not present across the entire basin.
The Purni Formation map is equivalent to the top Permian above where the formation exists.
Primary interpretation was from available digitized paper sections in 1999. Two way Time (TWT) digital data was cross correlated with a digital "warping field" derived from petroleum well depths to create a depth map. This is the equivalent to applying a velocity field.
A major update was completed in 2012 with the inclusion of all water bore, mineral hole, petroleum well and sub crop data. Limited, recent seismic data from the Northern Territory was incorporated where possible but poor ties exist to existing data due to limited digital data.
In 2015, recent bore hole data allowed further refinement of the map data to be made.

Top Crown Point Formation Depth (CP)
The Crown Point Formation is a fluvial glacial formation straddling the Carboniferous/Permian boundary. The top Crown Point pick generally falls on a weak seismic peak and fairly correlatable.
Final surface mapping was obtained by creating an isopach of the Purni Formation and subtracting it from the top Permian map.
A major update was completed in 2012 with the inclusion of all water bore, mineral hole, petroleum well and sub crop data. Limited, recent seismic data from the Northern territory was incorporated where possible but poor ties exist to existing data due to limited digital data.
In 2015, recent bore hole data allowed further refinement of the map data to be made.

Top Basement (Z)
The top Basement generally refers to the potential economic limit of the area. This is effectively the start of crystalline rock. Seismically this appears as a very high amplitude event and is often poorly correlatable. Drill hole intersections with Basement are limited in number.
Primary interpretation was from available digitized paper sections in 1999. Two way Time (TWT) digital data was cross correlated with a digital "warping field" derived from petroleum well depths to create a depth map. This is the equivalent to applying a velocity field. 
A major update was completed in 2012 with the inclusion of all water bore, mineral hole, petroleum well and sub crop data. Limited, recent seismic data from the Northern Territory was incorporated where possible but poor ties exist to existing data due to limited digital data.
In 2015, recent bore hole data allowed further refinement of the map data to be made.

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