Success in the Canning Basin

Case Study

Using FALCON AGG to Maximize the Value of Vintage 2D

Over recent years, AGG (Airborne Gravity Gradiometry) data has been increasingly used in oil and gas exploration in a variety of geological environments. The popularity of AGG data is largely due to its low cost, rapid acquisition and ability to add significant value to seismic data. Falcon® AGG is the only AGG system that has been custom designed for use in survey aircraft and as a result provides the highest resolution and lowest noise AGG data available. It is able to be deployed in both fixed wing and helicopter platforms enabling acquisition to be performed in all types of terrain.

Success in the Canning Basin

Introduction

Many frontier basins have widely spaced, vintage 2D seismic data available. The often poor quality of this vintage seismic makes it difficult to derive any meaningful geological information. By using additional complementary datasets, interpretation of the seismic data is often possible. Here we show how Falcon® Airborne Gravity Gradiometer (AGG) data combined with magnetic and other geological data has enabled a geological model to be constructed and vintage seismic to be interpreted. A workflow involving integrated interpretation of AGG, magnetic and seismic data is described using an example from the Canning Basin in northern Western Australia.

Canning Basin Survey

The Canning Basin in northern Western Australia is an under explored frontier basin. Most of the available information about the subsurface structure of the Canning Basin is generally restricted to relatively sparse vintage 2D seismic, a few wells and regional magnetic and gravity data.

To obtain an improved 3D understanding of the basin architecture and prospectivity, Buru Energy acquired a Falcon® AGG survey of some 38,800 km2 over the SW margin of the Fitzroy Trough and Gregory Sub-basin. The main objective of the survey was to improve understanding of the 3D geology of the survey area to better interpret existing seismic data, and to assist in the planning of further 2D and 3D seismic surveys.

Airborne Gravity Gradiometry Surveys in the Canning Basin provide a cost effective way of exploring. Buru’s exploration department use it on a daily basis to complement the sparse seismic control in order to fill in the geological blanks"

Interpretation

An interpretation of the 3D basin architecture was produced by applying a new method of integration of AGG and seismic data, including ‘vintage’ seismic data.

After an initial integrated structural interpretation, reinterpretation of selected seismic traverses and subsequent 2.5D gravity modelling was completed, incorporating information from AGG, seismic, magnetic and well data.  These modelled traverses were then used to produce a 3D geological model of the northern part of the survey area, resulting in an improved understanding of 3D distribution of structures and stratigraphy.

A sequence of Ordovician carbonate and shale bearing formations of relatively constant thickness overlying the metamorphic basement is clearly defined as gD and GDD highs in the AGG data. The fault structure of the platforms and terraces is well-defined by, with low GDD values in the fault heave areas of these formations. In the northern part of the survey, thickness variations in the Ordovician-Silurian Carribuddy Group are linked to large listric growth faults, defining the WNW Fitzroy Trough trend.

As a result of better 3D basin definition and detailed structural interpretation resulting from the AGG survey, Buru Energy is able to actively use this data to assist in seismic interpretation and in planning future exploration activities.

Conclusions

Maximizing the information derived from existing vintage 2D seismic can not only speed up the exploration cycle but can also reduce the overall cost. By undertaking integrated interpretation of the available vintage seismic data combined with AGG data, conceptual geological models can be developed. These models can be tested by 2.5D gravity modelling of the seismic interpretation which can then be extrapolated to produce 3D geological block models, de-risking and optimizing future seismic survey plans and improving the chances for discovery.

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