Unexpected HTI velocity anisotropy: a wide-azimuth, low fold, 3D seismic processing case study
Randall Taylor A , Simon Cordery A , Sebastian Nixon A and Karel Driml AA Velseis Processing Pty Ltd
B Origin Energy
The APPEA Journal 54(2) 1-5 https://doi.org/10.1071/AJ13003
Published: 2014
Abstract
This case-study demonstrates seismic processing in the presence of Horizontal Transverse Isotropic (HTI) velocity anisotropy encountered in a low-fold land 3D survey in New Zealand. The HTI velocity anisotropy was unexpected, being suspected only after the initial poor stack response compared to vintage 2D sections in the area, and the sparse 3D design made it difficult to identify. The paper shows how anisotropy was singled out from other possible causes, such as geometry errors. We discuss the key steps of the processing flow incorporated to deal with the HTI anisotropy to attain a high quality final processed volume. In particular we show data examples after the application of azimuthally dependant NMO velocities, along with pre-stack HTI migration. Examples are shown which demonstrate the preservation of the HTI anisotropy before and after 5D trace interpolation.
Maps and vertical profiles of 3D attributes are used to demonstrate the magnitude and direction of the HTI velocity field, which varies 5% to 10% between the fast and slow horizontal directions. These observations coincide with the local stress state deduced from borehole break-out studies. We conclude that the fast velocity direction corresponds to the present maximum horizontal stress direction. Finally the paper summarises the implications for processing wide azimuth 3D data in this area and suggests improvements for future 3D survey design.
This paper was originally published in the Proceedings of the 23rd International Geophysical Conference and Exhibition, which was held from 11–14 August 2013 in Melbourne, Australia.
Randall Taylor holds a Bachelor of Applied Science (Hons) in Geophysics from the University of Queensland, 1982. His present position is Chief Geophysicist for Origin Energy, where he is responsible for the application of geophysical technology. He commenced with Origin Energy in 2000 after six years with Oil Company of Australia as team leader in the Otway and Eromanga basins. Prior to this Randall was a senior geophysicist at Santos Ltd, conducting and overseeing seismic interpretation in a number of their operated permits in the Cooper and Carnarvon Basins, PNG and in the Timor Sea. He began his career in geophysics with CSR’s Oil and Gas Division, working mainly in the Denison and Surat basins. Member: ASEG, PESA, SEG, and EAGE. randall.taylor@originenergy.com.au |
Simon Cordery graduated with a bachelor’s degree in physics, and then a master’s degree in geophysics from Durham University in 1987. A few short years in aeromagnetic and seismic acquisition were followed by a long, varied and rewarding career in seismic processing, first at a number of locations with Shell, then with Velseis in Brisbane, Australia. Simon is presently working as a geophysical specialist with Saudi Aramco in Saudi Arabia. scordery@velseis.com.au |
Sebastian Nixon holds a Bachelor of Applied Science (Hons) in Geophysics degree from the University of Queensland, 2000. His present position is staff geophysicist for Origin Energy in the Offshore Otway Asset Development Team. In between regional interpretation projects, he meddles in the dark arts of seismic QI studies across the basin. He commenced with Origin in 2010 after two years with AWE as a geophysicist with their Regional New Ventures and Scouting Office in London, UK. Prior to this, Sebastian spent five years in Adelaide with Santos Ltd as an exploration geophysicist working in numerous offshore Australian-operated permits and International New Ventures and Regional Basin studies projects. He began his career in Brisbane as a graduate geophysicist with the Santos South East Asian Business focused on the East Java Basin. sebastian.nixon@originenergy.com.au |
Karel Driml is the founding managing director of Velseis Processing, which has been operating in Brisbane since 1992. Karel graduated from the University of Queensland in 1981, majoring in physics and mathematics. He has previously worked for Petty-Ray Geophysical and Digicon. At Velseis, Karel has developed processing and interpretation workflows for shallow coal high-resolution 3D seismic surveys. He has been responsible for introducing new processing technologies to Velseis. Karel has a great deal of experience with processing data from many of the onshore basins in Australia. kdriml@velseis.com.au |
