ACARP ACARP ACARP ACARP
Underground

Enhancing Fault Detection by Seismic Diffraction Imaging

Underground » Geology

Published: May 15Project Number: C22016

Get ReportAuthor: Binzhong Zhou, Peter Hatherly, Weijia Sun | CSIRO, Coalbed Geoscience, Chinese Academy of Sciences

Faults cause breaks in continuity of seismic horizons and at these discontinuities, diffraction patterns in seismic waves are generated. This is a well understood phenomenon but modern seismic acquisition and processing techniques are mainly directed towards providing high resolution images of the reflecting layers in the subsurface. Diffraction behaviour is largely ignored.

The potential for a diffraction analysis to reveal the locations of small faults and dykes that can impact on underground coal mine operations is therefore a fertile area for investigation. In this project, the objective was to undertake this investigation and establish whether diffraction analysis would allow identification of the location of small faults within 2D and 3D survey data. The study has involved computer generated synthetic seismic data and actual survey data from high resolution seismic surveys from Australian coal mines. It was anticipated that new processing techniques might need to be developed.

Extensive computer modelling of different geological scenarios encountered in coal mining allowed investigation of diffraction behaviour in both raw shot records and processed sections. Pre‐stack depth migration was shown to collapse diffractions and make the detection of small faults difficult. However, in conventional post stacked sections, diffractions are preserved and can be extracted by utilising relatively straightforward procedures aimed at removing reflection events from coal seams with relatively shallow dips. By comparison with stacked sections produced after the reflection data were removed from the shot records, it was found that normal moveout corrections and stacking do not adversely affect the diffraction behaviour. Diffractions can therefore be studied and extracted from conventional stacked seismic sections without the need for significant reprocessing.

Encouraged by these findings, 2D and 3D seismic survey data from the Sydney and Bowen Basins were studied. As far as possible, these data were selected from sites where mining or other geological information (mainly drilling) provides evidence for the true subsurface geology. It was found that diffractions could be observed in situations where the coal seams are relatively parallel and the coal seam of interest is mainly towards the top of the coal measure sequence. In terms of the size of the structures that were detected, the known faults for most of the examples studied had large throws and could also be detected by conventional reflection interpretation. In one case diffractions from a known fault with a throw of less than 1 m were detected, as were diffractions from dykes less than 4m wide. These were not detectable in the reflection data.

From the computer modelling study of small, 1m throw faults, it was found that diffractions are generated from these structures and that they are present on final stacked sections. In these situations, the reflection data are not able to define the faults and it is only by a diffraction analysis that their presence can be inferred. In addition to the example of actual fault and dyke detection provided above, other real seismic survey data also showed this same behaviour and diffractions were clearly present when there was no displacement evident in the reflection surface. Presumably these diffractions are associated with minor coal‐seam structures.

As far as the differences between 2D and 3D seismic surveying are concerned, it was observed that for both types of survey, diffractions were generated at geological structures. Survey geometry is therefore not an issue for diffraction studies. However, from the 3D survey data studied, it was observed that the dip on the diffraction hyperbola was greatest on lines perpendicular to the strike of the structure. This observation is consistent with expectations and adds a further reason to the generally accepted view that seismic investigations are best conducted with lines perpendicular to the structural trend of the area under investigation.

The computer modelling has also allowed investigation of different dyke scenarios (simple dyke, dyke within a shear zone, dyke and fault within a shear zone), and the effect of random noise on the seismic shot records, the type of seismic source (explosives versus lower frequency Vibroseis), the style of faulting (reverse fault versus normal fault) and the depth of fault. In all cases, diffractions are generated at the locations of the discontinuity in the reflecting surface. The field examples also demonstrate that the choice of seismic source and style of faulting do not present issues. As discussed above, igneous dykes have been shown to be valid targets for this approach.

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27039True Triaxial Strength Of Coal Measure Rocks And Its Impact On Roadway Stability And Coal Burst Assessment

Rocks in the ground are subject to a range of stresses. The stresses...

C3063Underground Vehicle Design Standards And Statutory Implications

The Australian underground diesel vehicle fleet has evolved since di...

C3064Conveyor Belting And Lagging Shear Characteristics - Drive Drum Slip

The primary aim of this project was to investigate the relationsh...

Underground

Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

C28033Raw Ash To Yield Relationships

Correct outcomes in yield predictions for product ash from coal bore...

C27038Establishing Self-Sustaining And Recognisable Ecological Mine Rehabilitation

In recent years an increasing interest has been placed on mining ope...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27064Dry Beneficiation Using FGX And X-Ray Sorters

Conventional dry processing methods engage a single beneficiation de...

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community

NERDDC

National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook

NERDDC