Beach Energy LtdHaselgrove 3D Seismic Data Re-processing, 2014

Quash X – Crosspread Adaptive Linear Noise Attenuation

Sept 3, 2014

• Very strong amplitude ground role is present on the data. The amplitude of this noise is an ordermagnitude stronger than the signal. This ground roll is quite limited in bandwidth.• A two tiered approach was utilized to remove this energy. The process is known as Quash-X, where the X signifies that the processing takes place in the “Cross-Spread” domain.• The process works by estimating the noise in some fashion, within a defined 3D cone centred on the middle of the Cross-Spread, and then adaptively subtracting the data across 3D windows. • The first pass Quash X exploited the band-limited nature of the noise, along with an “power-expansion” process to enhance the high amplitude noise and de-enhance the low amplitude signalwithin the band being examined. The noise model is then adaptively subtracted from the original gather in a similar way to the adaptive subtraction methodology used in marine SRME.The end resultis that only noise within the defined 3D cone, and only high-amplitude energy is affected. Outside the cone, the gather is un-modified.• The second pass Quash X (QuashXX) utilized a 3DFK filter to build the noise model within the 3D cone. This noise model is again adaptively subtracted from the Quash X gather. The data outside the cone is again unmodified.• Selected receiver lines with the cross-spread (small offset, mid offset and large offset) are displayed raw, and with QuashX and QuashXX. The difference between the raw gather and each isalso shown.• A selection of inline and crossline stacks are displayed raw, with Quash X and with Quash XX.The impact on the stacked data is less than observed on the gathers as expected, however theprocess will be significant when the data is interpolated and migrated pre-stack.

Raw Receiver Line from X-Spread (Mid Offset Rx Line)

Raw Receiver Line from X-Spread (Mid Offset Rx Line)

Quash X Receiver Line from X-Spread (Mid Offset Rx Line)

Quash XX Receiver Line from X-Spread (Mid Offset Rx Line) 2nd Pass Quash

Difference Raw-Quash X Receiver Line from X-Spread (Mid Offset Rx Line)

Difference Raw-Quash XX Receiver Line from X-Spread (Mid Offset Rx Line)

Raw Receiver Line from X-Spread (Near Offset Rx Line)

Quash X Receiver Line from X-Spread (Near Offset Rx Line)

Quash XX Receiver Line from X-Spread (Near Offset Rx Line) 2nd Pass Quash

Difference Raw-Quash X Receiver Line from X-Spread (Near Offset Rx Line)

Difference Raw-Quash XX Receiver Line from X-Spread (Near Offset Rx Line)

Raw Receiver Line from X-Spread (Far Offset Rx Line)

Quash X Receiver Line from X-Spread (Far Offset Rx Line)

Quash XX Receiver Line from X-Spread (Far Offset Rx Line) 2nd Pass Quash

Difference Raw-Quash X Receiver Line from X-Spread (Far Offset Rx Line)

Difference Raw-Quash XX Receiver Line from X-Spread (Far Offset Rx Line)

Example Inlines – Pre-Quash

Example Inlines – After First Pass Quash (Quash X)

Example Inlines – After Second Pass Quash X (Quash XX)

Example Xlines – Pre-Quash

Example Xlines – After First Pass Quash (Quash X)

Example Xlines – After Second Pass Quash X (Quash XX)