Seismic AVAZ inversion for orthorhombic shale reservoirs in the Longmaxi area, Sichuan
Luo Teng, Feng Xuan, Guo Zhi-Qi, Liu Cai, and Liu Xi-Wu
1 College of Geo-Exploration Science and Technology, Jilin University, Changchun 130026, China
2 State Key Laboratory of Shale Oil and Gas Enrichment Mechanism and Effective Development, Beijing 100083, China
3 SinoPEC Key Laboratory of Shale Oil/Gas Exploration and Production Technology, Beijing 100083, China
4 SinoPEC Petroleum Exploration and Production Research Institute, Beijing 100083, China
Abstract Seismic AVAZ inversion method based on an orthorhombic model can be used to invert anisotropy parameters of the Longmaxi shale gas reservoir in the Sichuan Basin.. As traditional seismic inversion workflow does not sufficiently consider the influence of fracture orientation, we predict fracture orientation using the method based on the Fourier series to correct pre-stacked azimuth gathers to guarantee the accuracy of input data, and then conduct seismic AVAZ inversion based on the VTI constraints and Bayesian framework to predict anisotropy parameters of the shale gas reservoir in the study area.We further analyze the rock physical relation between anisotropy parameters and fracture compliance and mineral content for quantitative interpretation of seismic inversion results. Research results reveal that the inverted anisotropy parameters are related to P- and S-wave respectively, and thus can be used to distinguish the effect of fracture and fluids by the joint interpretation. Meanwhile high values of anisotropy parameters correspond to high values of fracture compliance, so the anisotropy parameters can reflect the development of fractures in reservoir. There is two sets of data from different sources, including the content of brittle mineral quartz obtained from well data and the anisotropy parameters inverted from seismic data, also show the positive correlation. This further indicates high content of brittle mineral makes fractures developing in shale reservoir and enhances seismic anisotropy of the shale reservoir. The inversion results demonstrate the characterization of fractures and brittleness for the Longmaxi shale gas reservoir in the Sichuan Basin.
This work was supported by the National Key S&T Special Project of China (No. 2017ZX05049-002), the NSFC and SinoPEC Joint Key Project (No. U1663207), and the National Natural Science Foundation of China (No. 41430322).
About author: Luo Teng is a PhD student at Jilin University. He obtained his M.S. from the College of Geo-Exploration Science and Technology at Jilin University in 2015. His main research interests are forward modeling and inversion of seismic anisotropies. E-mail :autumn 2009lt@126.com Guo Zhiqi is a professor at Jilin University. His research interests are petrophysics, reservoir modeling, and seismic anisotropy. E-mail: guozhiqi@jlu.edu.cn
Cite this article:
. Seismic AVAZ inversion for orthorhombic shale reservoirs in the Longmaxi area, Sichuan[J]. APPLIED GEOPHYSICS, 2019, 16(2): 195-209.
2019, Vol. 16 
