We would like to thank Vladimir Bashkardin, Hesam Kazemeini, Siwei Li, Yang Liu, and Xiaolei Song for helpful suggestions and Peter Eichhubl and Pete Hargrove for providing the example fracture map. We would also like to thank the three anonymous reviewers for comments helpful in improving this paper. Funding for this project is provided by RPSEA through the ``Ultra-Deepwater and Unconventional Natural Gas and Other Petroleum Resource'' program authorized by the U.S. Energy Policy Act of 2005. RPSEA (www.rpsea.org) is a nonprofit corporation whose mission is to provide a stewardship role in ensuring the focused research, development and deployment of safe and environmentally responsible technology that can effectively deliver hydrocarbons from domestic resources to the citizens of the United States. RPSEA, operating as a consortium of premier U.S. energy research universities, industry, and independent research organizations, manages the program under a contract with the U.S. Department of Energy's National Energy Technology Laboratory.