1. Formerly Massachusetts Institute of Technology, Department of Mathematics and Earth Resources Laboratory, 77 Massachusetts Ave, Cambridge, Massachusetts 02139, USA, University of California Irvine, Department of Mathematics, 540 Rowland Hall, Irvine, California 92963, USA; currently Lawrence Berkeley National Laboratory, Computational Research Division, 1 Cyclotron Road, Berkeley, California 94720, USA.(corresponding author).
2. Formerly Massachusetts Institute of Technology, Department of Mathematics and Earth Resources Laboratory, 77 Massachusetts Ave, Cambridge, Massachusetts 02139, USA; currently Université Catholique de Louvain, Institute of Information and Communication Technologies, Electronics and Applied Mathematics, 4, Avenue G. Lemaitre, Louvain-la-Neuve B-1348, Belgium..
3. Formerly Total E&P Research & Technology USA, LLC, 1201 Louisiana St., Suite 1800, Houston, Texas 77002, USA; currently Virginia Tech, Department of Mathematics, 460 McBryde Hall, 255 Stanger St., Blacksburg, Virginia 24061, USA..
4. Massachusetts Institute of Technology, Department of Mathematics and Earth Resources Laboratory, 77 Massachusetts Ave, Cambridge, Massachusetts 02139, USA..