Fluids discrimination by ray-path elastic impedance inversion: A successful case from Sulige tight gas field
Wang Da-Xing, Wang Hao-Fan, Ma Jin-Feng, Wang Yong-Gang, Zhang Na, Li Lin, Jia Ling-Yun, and Yang Yang
1. Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Shaanxi, Xi’an 710018,China.
2. National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Field, Shaanxi, Xian 710018, China.
3. National & Local Joint Engineering Research Center of Carbon Capture and Storage Technology, Department of Geology,Northwest University, Shaanxi, Xi’an 710069, China.
Abstract Existing seismic prediction methods struggle to effectively discriminate between fluids in tight gas reservoirs, such as those in the Sulige gas field in the Ordos Basin, where porosity and permeability are extremely low and the relationship between gas and water is complicated. In this paper, we have proposed a comprehensive seismic fluid identification method that combines ray-path elastic impedance (REI) inversion with fluid substitution for tight reservoirs. This approach is grounded in geophysical theory, forward modeling, and real data applications. We used geophysics experiments in tight gas reservoirs to determine that Brie’s model is better suited to calculate the elastic parameters of mixed fluids than the conventional Wood’s model. This yielded a more reasonable and accurate fluid substitution model for tight gas reservoirs. We developed a forward model and carried out inversion of REI, which reduced the non-uniqueness problem that has plagued elastic impedance inversion in the angle domain. Our well logging forward model in the ray-path domain with different fluid saturations based on a fluid substitution model proved that REI identifies fluids more accurately when the ray parameters are large. The distribution of gas saturation can be distinguished from the crossplot of REI (p= 0.10) and porosity. The inverted ray-path elastic impedance profile was further used to predict the porosity and gas saturation profile. Our new method achieved good results in the application of 2D seismic data in the western Sulige gas field.
This work was supported by the National Science and Technology Major Project (No. 2016ZX05050 and 2017ZX05069),and CNPC Major Technology Special Project (No. 2016E-0503).
Corresponding Authors: Wang Hao-Fan (Email: wanghf@nwu.edu.cn)
E-mail: wanghf@nwu.edu.cn
About author: Wang Da-Xing, Ph.D., he received the B.S. and M.S. degrees in geophysical exploration from the Southwest Petroleum University, Sichuan, China, in 1983 and 1995, respectively, and the Ph.D. degree in solid geophysics from the Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, in 2005. He is currently a Professor-level Senior Engineer with the Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi’an, China. His research interests include reservoir prediction and hydrocarbon detection. Email: wdx1_cq@petrochina.com.cn.
Wang Hao-Fan, she earned the B.S. and M.S. degrees in geodetection and information technology from Department of Geology, Northwest University in 2014 and 2017. She is currently an experimental technician in Department of Geology of Northwest University. Her research interests are seismic forward and inversion, and CO2 geological storage. Email: wanghf@nwu.edu.cn.
Cite this article:
. Fluids discrimination by ray-path elastic impedance inversion: A successful case from Sulige tight gas field[J]. APPLIED GEOPHYSICS, 2019, 16(2): 231-245.
2019, Vol. 16 
