As the down-turn in the oil and gas industry started 2 years ago, SIP took a brave and strong decision to invest in R&D to implement the next generation of imaging algorithms to address the major seismic data challenges, reducing risk and uncertainty for our clients, and obtaining the highest quality seismic products for hydrocarbon exploration and production. SIP have focused on the following 3 major developments: 1) Ray based imaging algorithms- single arrival vs multi arrival (Kirchhoff vs GRT) 2) Wave based imaging algorithms- Extended full guided wave imaging (RTM/WEM/Beam vs eGWM-much faster than current industry imaging algorithms- results to be published soon) 3) Velocity Model Building – eFWI using AutoImager velocity model as starting model (Tomography vs eFWI- includes refraction and reflection energy) This article explains the raytracing methods and the advantages of multi arrival imaging for AVO/AVA exploitation.

1. GRT imaging for seismic AVO/AVA inversion -
significantly reducing amplitude uncertainty
and obtaining more accurate elastic
attributes

2. Introduction: As the down-turn in the oil and gas industry started 2 years ago,
SIP took a brave and strong decision to invest in R&D to implement the next
generation of imaging algorithms to address the major seismic data challenges,
reducing risk and uncertainty for our clients, and obtaining the highest quality seismic
products for hydrocarbon exploration and production. SIP have focused on the
following 3 major developments:
1. Ray based imaging algorithms- single arrival vs multi arrival (Kirchhoff vs GRT)
2. Wave based imaging algorithms- Extended full guided wave imaging
(RTM/WEM/Beam vs eGWM-much faster than current industry imaging
algorithms- results to be published soon)
3. Velocity Model Building – eFWI using AutoImager velocity model as starting
model (Tomography vs eFWI- includes refraction and reflection energy)
This article explains the raytracing methods and the
advantages of multi arrival imaging for AVO/AVA
exploitation.
Introduction

3. The Issue: standard imaging workflows and algorithms using Kirchhoff have
led to the following:
1. A multitude of examples of the industry drilling dry holes on AVO
prospects. It could be due to genuine rock physics ambiguity or
misconceptions on the gathers output from Kirchhoff Time or Depth
migration:
– Anisotropy, Tuning, denoise, RMO, TRIM Statics, Offset balancing
– Modelling gathers to look for match with seismic
2. There is considerable effort to make gathers appear clean & flat using data
conditioning tools instead of asking more fundamental questions on the
accuracy of the velocity model and imaging. Our expectations from any
migration code is:
– Denoise using absorbing boundary conditions.
– Accurate Velocity & Eta -- so no requirement for subsequent RMO.
– Spherical divergence corrections -- so no requirement to match modelled gathers with
offset scaling.
– Ability to accurately handle and image multi-arrival travel times.
We compare the current standard Kirchhoff code to a more advanced multi arrival
imaging algorithm. We refer to this as GRT- Generalized Radon Transform- angle
domain depth Imaging.
Problems/Issues

4. • Kirchhoff will image only one arrival, whereas GRT is a multi-arrival code
hence preserves the amplitudes and the structural definition with much
more clarity and detail. As shown in the figure below.
GRT Concept

5. Why the seismic industry needs a multi arrival imaging code?
• It is apparent that many of companies in the industry are putting a lot of effort in
getting the right seismic data by adopting the latest and greatest acquisition techniques
coming on to the market. For example – dense cables / dense receivers / dense nodes /
dense shooting patterns / sim sources or blended acquisitions / etc. Most (more than
40%) of the acquired data is redundant and discarded during the regularization stage of
the seismic processing, and also when the remaining data is passed through Kirchhoff
PSDM. This is where the imaging code will only image single arrivals thus generates a
lot of noise and most importantly loses the information from the arrivals of different ray
paths, which may contain the true amplitudes of the reflected events of the subsurface.
GRT Concept

6. The Solution and Examples
• So far SIP (Seismic Image processing Ltd) have completed numerous production jobs to
validate the GRT PSDM against the industry Kirchhoff PSDM imaging code. GRT
produces more reliable true amplitude information where the AVA theory holds true.
Project after project we have experienced significantly higher quality images to map
new exploration targets, including proof of dry holes that had been originally drilled
using Kirchhoff PSDM images, which had falsified the amplitudes (see the examples
below)

7. The Solution and Examples
NOTE: the ringing event on the Kirchhoff
image (below left)looks like a residual
multiple which is not present on the image
with multi-arrival code (GRT). Also the faults
are clearly sharper with less noise and less
smearing across the fault boundary

8. Conclusions
AVA- Elastic attributes example
Conclusions: So far all the GRT projects have delivered superior results compared to Kirchhoff. It is time for
the industry to move on to a new generation of imaging codes and workflows to reduce the risk and
uncertainty of understanding the amplitudes of the true reflectivity of the subsurface.
Seismic Image processing Ltd is offering our velocity model building and GRT solutions to many clients across
Norway and UK. All our PSDM projects have been through GRT imaging. Any questions and clarifications
please send an email to admin@seismicimageprocessing.com; Jagat.deo@seismicimageprocessing.com;
• Please visit our website: http://www.seismicimageprocessing.com/