1. Xi’an Jiaotong University, School of Mathematics and Statistics, Xi’an, China.
2. Xi’an Jiaotong University, School of Mathematics and Statistics, Xi’an, China. (corresponding author)
3. China University of Petroleum (Beijing), State Key Laboratory of Petroleum Resources and Prospecting, Beijing, China and China University of Petroleum (Beijing), National Engineering Laboratory of Offshore Oil Exploration, Beijing, China.
4. The University of Texas at Austin, John A. and Katherine G. Jackson School of Geosciences, Bureau of Economic Geology, Austin, Texas, USA.