Challenges when imaging 3D UHRS data and their equivalent in "conventional" seismic acquisition
Imagine processing conventional 3D seismic data that had been acquired during a 100m swell. Sounds crazy, right?
At RockWave we have a unique perspective on seismic acquisition, because we get to experience data that span huge frequency ranges (<2 Hz – 20 kHz) acquired by a wide variety of vessels and survey contractors.
What we often call “conventional” seismic is typically used for O&G exploration or 4D monitoring and operates in the <2-250 Hz range to image targets thousands of metres deep.
Whereas ultra-high resolution seismic (UHRS) is used for imaging the upper 100m of subsurface for wind farm arrays and cable routes.
It may surprise people to know, that there is a simple scalar that can transport you from the worlds of conventional to UHRS seismic acquisition…
Multiply by 50
For example, 120m cable towed from the back of a shallow seismic vessel is the equivalent to a 6000m cable in the conventional seismic world. Seems sensible.
But more impressively, and illustrating the challenges we face when processing and imaging ultra-high resolution seismic data, a wave height of 2m during a UHRS acquisition is the equivalent to 100m in the conventional world!
Is there a seismic operations manager on the planet who would choose to leave their equipment in the water and shoot seismic during a 100m swell?
HSSE moment anyone?
Nick Woodburn, in preparation for his talks for the GESGB and Geophysical Society Houston (GSH) in December 2023, has been creating 3D synthetics to illustrate some of the practical challenges faced when acquiring and processing 3D UHRS data compared to conventional data.
The image above shows the significant impact of a 2m sea-surface wave motion on UHRS data. (a) Synthetic seismic data representing conventional seismic, acquired with a flat 9m cable. A sample NMO-corrected CMP gather is shown alongside the raw stack with a velocity overlay. (b) Synthetic seismic generated through a scaled (x50) version of the velocity model to represent UHRS data. In this instance the sea-surface wave motion, which has a nominal height of 2m, greatly impacts the reflection signal shown in the CMP gather and raw stack.
Nick will be presenting his findings, which expand upon the talk given earlier this year at EAGE Near Surface in Edinburgh, within his talk titled, “Practical considerations for optimising 3D ultra-high resolution seismic” at the following two events:
6th December 2023: Geophysical Society Houston (GSH) 5th Annual Web Symposium “3D Seismic Survey Design” 9am-1:30pm CDT
14th December 2023: GESGB Geophysics Seminar 2023 - Events @ No.6, 6 Alie Street, London, E1 8QT, United Kingdom – 9am-6pm GMT
To register for these events use the two links below:
Registration for GSH 5th Annual Web Symposium: https://www.gshtx.org/SharedContent/Events/Event_Display.aspx?EventKey=19d8fd2e-b7f6-435c-84f2-67ff7cbb4ebf&WebsiteKey=955f17e6-46ad-4401-acbd-2af6c393752b
Registration for GESGB Geophysics Seminar:
We look forward to having many more discussions on 3D UHRS in the coming months as we continue pushing for widespread adoption of 3D in the shallow seismic world.