Stephen J. Sullivan represents clients in all aspects of natural resources with a primary focus on oil and gas exploration and development in the Rocky Mountain area. A large part of his oil and gas practice involves acquisitions and divestitures as well as operational matters. Mr. Sullivan represents mining companies from the initial staking of claims through financing, permitting, and start-up of mining operations. He also represents parties in the purchase of ranches and in the acquisition and sale of water rights in Colorado, including acquisition of water rights and construction of water delivery systems.

Real estate transactions in which Mr. Sullivan has been involved – in both negotiation and legal representation – include land exchanges, open space dedication, mineral development agreements and intergovernmental agreements for construction of transportation and water infrastructure, and development of commercial properties.

Representative Matters

Oil and Gas:

  • Simultaneous purchase from multiple parties and sale of approximately 100 wells and 23,000 acres of producing and undeveloped coal bed methane properties in the San Juan Basin.
  • Multi-stage sale and agreement for joint development affecting 350,000 acres of producing and undeveloped properties in Colorado's DJ Basin.
  • Due diligence for acquisition of 40,000 acres of undeveloped leases in Wyoming's Niobrara shale play.
  • Practice before the Colorado and Wyoming Oil and Gas Conservation Commissions.


  • Due diligence for acquisition of mineral properties and operating mines in Colorado, Nevada, Wyoming and California.
  • Formation of mining companies, followed by location and development of uranium mining claims and subsequent consolidation, permitting, construction, operation and ultimate sale of a mine in San Juan County, Utah.
  • Due diligence for both purchase and sale of two operating coal mines in the Powder River Basin, Wyoming.


  • Due diligence for acquisition of 588,000 acre Vermejo Park Ranch and negotiation of subsequent mineral development agreements.
  • Purchase of land and water rights for an 80,000 acre Colorado ranch, followed by timber management negotiations, ranch management issues and creation of a conservation easement.
  • Sale of 2,500 acre Garfield County (Colorado) ranch and mineral rights to major oil and gas company.


  • Acquisition and management of multiple Rocky Mountain Fuel properties in Colorado, including surface leases, water rights, mineral rights, and coal and oil and gas royalties, covering approximately 32,000 acres.
  • Due diligence for acquisition of wind power properties and easements in eastern Colorado.

Publications, Presentations & Accolades

  • Steward of Industry Award, Denver Section of the Society of Petroleum Engineers ("SPE"), 2018
  • Top Lawyers, Natural Resources, 5280 - The Denver Magazine, 2017-2019
  • Board Member, The Colorado Oil and Gas Association (1995-present)
  • Mayor of the Town of Foxfield, 2002-2008
  • Board Member, Town of Foxfield, 1998-2008
  • Board Member, Volunteers for Outdoor Colorado, 1990-1994
  • Distinguished Service Award, Rocky Mountain Association of Geologists, 1990


Steve Sullivan's experience in natural resources and the Rocky Mountain west began long before he began his legal career. His experiences on ranches in Wyoming and Nevada provide perspective when addressing land transactions and negotiations between mineral and surface owners. During the energy boom and bust of the 1970s his education included research on the supply of ground water for coal pipeline slurries, engineering of solar and geothermal homes in the Northern Rockies, uranium resource economics and supply, and geologic field work in five western states. He firmly believes that knowledge of the land and the people that live on the land are crucial to providing top notch legal representation and obtaining lasting solutions for his clients.

Mr. Sullivan's passion for the outdoors was fed by wilderness climbing trips, work on his grandfather's ranch, and long days in the prairies and foothills where he learned firsthand how wildlife adapts to changes caused by human development. Technical experience gained from work such as his study while at Princeton University of radioactive leakage into groundwater systems, work for the National Academy of Science on mined land reclamation in Wyoming's Powder River Basin, and modeling of resource availability for the federal government's energy supply models while working in Palo Alto, California provide him with insight on the complexities of issues related to natural resources from the perspective of scientist, developer, land owner and government regulator. This knowledge and experience allows him to focus immediately on key issues and provide timely advice.

His community involvement in Volunteers for Outdoor Colorado, Denver Earth Resources Library, and as a soccer coach evolved into ten years of service as trustee and mayor for the Town of Foxfield and member of the executive council of the Metro Mayors Caucus. Since 1995, Mr. Sullivan has also served on the board of the Colorado Oil and Gas Association. He particularly enjoys taking a "hands-on" approach, whether in negotiations or through direct personal interaction with the people affected.

* Per Wyoming Rule of Professional Conduct 7.1 (c), the descriptions of our fields of practice do not state or imply certification, specialization or expertise in any particular area of law, unless the description specifically states that the particular lawyer holds a certification or other expertise recognized by the applicable State Bar or regulatory authority.

Stephen J. Sullivan

Practice Areas
  • Oil and Gas
  • Real Estate
  • Acquisitions & Divestitures
  • Land Use
  • Mineral Title
  • Local Government
  • Water Rights

  • B.A. in geology, Princeton University, magna cum laude, Sigma Xi, 1977
  • M.S. in Energy and Resources, University of California, Berkeley, with honors, 1979
  • J.D., University of Denver, with honors, 1982

Bar Admissions / Qualifications
  • Colorado, 1982
  • Wyoming*, 1996
  • U.S. District Court, District of Colorado, 1982
  • U.S. Court of Appeals, Tenth Circuit, 1982

Professional & Community Activities
  • Colorado Bar Association
  • Denver Bar Association
  • Wyoming Bar Association*
  • Rocky Mountain Association of Geologists (Distinguished Service Award, 1990)
  • Town of Foxfield
  • Metro Mayors Caucus