Seismic petrophysics focused case study for AVA modelling and pre-stack seismic inversion
Jahan Zeb A , Sanjeev Rajput B and Jimmy Ting CA PETRONAS
B Baker Hughes, Malaysia
C CGG
The APPEA Journal 56(1) 341-354 https://doi.org/10.1071/AJ15025
Published: 2016
Abstract
Hydrocarbon reservoirs are characterised by integrating seismic, well-log and petrophysical information, which are dissimilar in spatial distribution, scale and relationship to reservoir properties. Well logs are essential for amplitude versus offset (AVO) modelling and seismic inversion. The usability of well logs can be determined during wavelet estimation, seismic-to-well ties, background model building, property distribution for inversion, deriving probability density functions and variograms, offset-to-angle conversion of seismic data, and many other processes. For the implementation of seismic inversion workflows, accurate and geologically corrected compressional-sonic, shear-sonic and density logs are necessary. Preparing the logs for quantitative interpretation becomes challenging in a real-field environment because of bad borehole conditions including washouts, uncalibrated and variability of logging tools, invasion effects, missing shear logs and change of borehole size. Conventional petrophysical analysis is usually restricted to the reservoir interval, the calculation of reservoir versus non-reservoir (including sands or shales), and log corrections for smaller intervals; in contrast, seismic petrophysics encompasses the entire geological interval, calculates the volume of multi-minerals, incorporates boundaries between non-reservoir and reservoir, and often includes the prediction of missing compressional and shear-sonic for AVO analysis.
A detailed seismic petrophysics analysis was performed for amplitude versus angle (AVA) modelling and attributes analysis. To perform the AVA modelling, a series of forward models in association with rock physics modelled fluid-substituted logs were developed, and associated seismic responses for various pore fluids and rock types studied. The results reveal that synthetic seismic responses together with the AVA analysis show changes for various lithologies. AVA attributes analysis show trends in generated synthetic seismic responses for various fluid-substituted and porosity logs. Reservoir modelling and fluid substitution increases understanding of the observed seismic response. This paper describes detailed data analysis using various techniques to confirm the rock model for petrophysical evaluation, rock physics modelling, AVA analysis, pre-stack seismic inversion, and the scenario modelling applied to the study of an oil field in Australia.
Jahan Zeb is a Specialist QI Geophysicist presently with PETRONAS, Malaysia. He obtained a BSc in physics and mathematics in 1997 from Peshawar University (Pakistan) and a MSc in geophysics in 2000 from Quaid-e-Azam University (Islamabad, Pakistan). He began his career in 2000 with Oil and Gas Development Corporation (Pakistan) before joining Schlumberger as a petrophysicist in 2001. Jahan has diverse experience in the international oil and gas industry, providing petrophysical advice to drilling operations, asset teams, and field production operations to enhance operational decision making. He joined Fugro-Jason (now CGG-Jason) in 2007 as a Principal Project Geoscientist and moved on as Regional Senior Petrophysics Advisor. During his stay with CGG, Jahan was involved in seismic petrophysics, rock physics modelling, and seismic inversion work. Jahan joined PETRONAS in 2015 as a Specialist Geophysicist. His work is primarily on rock physics modelling, seismic petrophysics, and seismic inversion for reservoir characterisation. jahanzeb.ahmed@petronas.com.my |
Sanjeev Rajput is a Principal Advisor Geophysics, Oil and Gas Development with Baker Hughes, Malaysia. He has 15 years of diverse experience in the oil and gas industry. Sanjeev obtained a BSc in physics and mathematics in 1998 from M.J.P. Rohilkhand University (India), and a Master of Technology in Applied Geophysics in 2001 from Kurukshetra University (India). In 2007 Sanjeev graduated with a PhD from Kurukshetra University, specialising in 4C seismic data analysis and quantitative interpretation. Sanjeev began his career as a marine geophysicist with CGG International, before studying for his post-doctorate fellowship with the University of Texas. As a reservoir geophysicist with Schlumberger in 2007 Sanjeev was involved in full field review, mature field development and quantitative interpretation of geophysical data. He joined CSIRO Australia in 2009 as a Senior Research Scientist and moved on as Principal Scientist. His consulting work was focused on geophysical data analysis and quantitative interpretation of oil and gas fields. Sanjeev joined Baker Hughes in 2013 in Kuala Lumpur, Malaysia. His work is primarily on mature oil and gas field development, unconventional hydrocarbon exploration and development, quantitative interpretation and production enhancement. Sanjeev has authored papers for more than 50 international publications, and two textbooks on unconventional hydrocarbons. Member: SEG, EAGE, and SPE. Sanjeev.Rajput@Bakerhughes.com |
Jimmy Ting is a Product Strategy Manager with CGG, United States. He obtained a BSc in applied geology in 1991 from University of Malaya in Malaysia, with a special interest in carbonate rocks. He has 25 years of diverse experience in the oil and gas industry. Jimmy began his career as a Seismic Processing Geophysicist with Shell in 1991, with both land and marine seismic processing experience. Jimmy moved on to special studies/quantitative interpretation in 1994, where he gained his experience in seismic inversion, AVO analysis, velocity modelling, pore pressure prediction, quantitative interpretation, and reservoir characterisation. In 1997, Jimmy joined Jason Geosystems in Singapore as international staff supporting Jason’s business in the Asia Pacific and Middle East. Jason Geosystems was acquired by Fugro in 2001 and by CGG in 2012. During the past 19 years, Jimmy has provided seismic reservoir characterisation and modelling studies for clastics, carbonates and unconventional reservoirs at all lifecycle stages of oil and gas fields. Presently, Jimmy looks after the software product enhancement and development for Geostatistical Reservoir Characterisation and Rock Physics based on customer feedback, technology advancement in the industry, and internal research. jimmy.ting@cgg.com |
