Management Team



    Lisa A. Stewart

    Executive Chairman and

    Chief Investment Officer


    Lisa Stewart serves as Executive Chairman, President, Chief Executive Officer and Chief Investment Officer and oversees all aspects of Sheridan acquisitions and the implementation of Sheridan’s strategy. Ms. Stewart brings over 30 years of experience in the oil and gas industry in engineering and management positions. Prior to founding Sheridan I in 2007, Ms. Stewart served as Executive Vice President of El Paso Corporation and President of El Paso E&P and other non-regulated businesses. In those positions, Ms. Stewart had overall responsibility for a large and diverse E&P company that generated operating revenue of $1.8 billion and earnings of $699 million during the twelve months ended June 30, 2006, and that had 2006 budgeted capital expenditures exceeding $1 billion. During her time at El Paso E&P, Ms. Stewart was responsible for a substantial turnaround in profitability and drilling success in what had been a distressed business. Her success was achieved by rebuilding the division, including reorganizing and recruiting a substantially new management team, infusing a culture of teamwork and accountability and focusing on profitability rather than solely on production growth. Prior to her time at El Paso, Ms. Stewart spent 20 years at Apache, leaving in January 2004 as Executive Vice President with responsibility for reservoir engineering, business development, land, environmental, health and safety and corporate purchasing. Ms. Stewart holds a B.S. in Petroleum Engineering from the University of Tulsa, where she is a member of the College of Engineering and Natural Sciences Hall of Fame. She is a member of the Society of Petroleum Engineers and IPAA and serves on the Board of Directors of Cimarex Energy Co.



    Thomas E. Voytovich

    Vice President and

    Chief Operating Officer


    Tom Voytovich joined Sheridan Production Company in December 2015 as Vice President and Chief Operating Officer with management responsibility for Sheridan’s technical and operational functions. Mr. Voytovich has over 38 years of industry experience. Prior to joining Sheridan, he spent 22 years at Apache Corporation in roles of increasing responsibility including Reservoir Engineer, Geological Advisor, Exploration Manager, Vice President of Apache’s Central Region (Oklahoma, the Permian Basin and East Texas) and Vice President and General Manager of Apache Egypt Companies, where he managed the activities of two joint venture companies as well as relations with the national oil company of Egypt (EGPC). In February 2013 Mr. Voytovich was named Executive Vice President of International, responsible for the company’s assets in Argentina, Australia, Canada, Egypt and North Sea. In January 2014, he became Apache’s COO-International with management responsibility for global operations outside of onshore North America. In June 2015, he was appointed Apache’s Executive Vice President of International, Offshore and Technology. Prior to Apache, he served as Exploration Manager of Hillin-Simon Oil Company, worked as a geologist for Berexco Inc, and served in roles of increasing responsibility in both geology and engineering for Petro-Lewis Corporation and Shell Oil Company. Mr. Voytovich holds a B.S. in Geological Engineering from Michigan Technological University and has been a Member of the Academy of Geological and Mining Engineering and Sciences at Michigan Tech since 2014. He is a certified Petroleum Geologist and is a member of the American Association of Petroleum Geologists.



    Michael Bose

    Vice President of Operations


    Michael Bose, Sheridan’s Vice President of Operations, has more than 25 years of engineering and management experience.  He joined Sheridan in 2017 after a short stint in private equity with Atalaya Resources in Tulsa.  Prior to that, he spent 10 years at Apache and 12 years at Anadarko. His experience includes positions of increasing responsibility throughout the engineering organizations of both companies and across a broad range of disciplines and geography. Michael’s more recent roles include Operations Manager, Production Manager, Exploitation Manager and Region Vice President at Apache.



    Mark Miertschin

    Vice President of Business

    Development and Marketing


    Mark Miertschin serves as Sheridan’s Vice President of Business Development & Marketing. Before joining Sheridan in 2007, he was Business Development Manager for El Paso E&P. Previously, Mr. Miertschin served as Gulf of Mexico Planning Manager for Unocal, Acquisitions Manager for Nuevo Energy and South America Business Development Manager for Atlantic Richfield Corporation. He holds a B.S. in Civil Engineering and an M.S. in Petroleum Engineering from The University of Texas and an M.B.A. from the University of Houston. Mr. Miertschin is a member of the Houston Producers Forum.



    Cheryl S. Phillips

    Vice President, General Counsel,

    Chief Compliance Officer and Secretary


    Cheryl S. Phillips serves as Sheridan’s Vice President, General Counsel, Chief Compliance Officer and Secretary. Before joining Sheridan in 2014, she was a partner in the law firm of Andrews Kurth LLP, where her practice focused primarily on oil and gas transactions. She has extensive experience with negotiation of oil and gas acquisition, divestiture and joint venture agreements, as well as a broad range of experience handling other oil and gas exploration and production transactions. Ms. Phillips began her legal career in 1989 with Mayor, Day, Caldwell & Keeton, LLP, where she practiced until its merger with Andrews Kurth LLP in 2001. She holds a J.D. from the University of Houston Law Center and a B.A. in Biology and Political Science from Rice University.



    Aaron Skidmore
    Vice President and
    Chief Financial Officer

    Mr. Skidmore joined Sheridan in January 2019 as Manager, Planning and Investor Relations and was named Vice President, Chief Financial Officer in August 2019.  Mr. Skidmore has over 14 years of experience in Treasury, Accounting and Finance, most recently with Cobalt International Energy, where he served as Treasurer and Director of Investor Relations.  Before joining Cobalt, he held roles of increasing responsibility with LyondellBasell Industries and Oasis Petroleum, after starting his career with PricewaterhouseCoopers.  He holds a B.S. in Accounting from Brigham Young University.



    Bart P. Hartman, III (Trey)

    Vice President and Controller

    Mr. Hartman joined Sheridan as Controller in November 2015 and was named Vice President and Controller in March 2017.  Prior to Sheridan, Mr. Hartman was employed at Halcon Resources Corporation commencing in 2012 in Vice President – Controller and Vice President – Internal Audit positions.  Prior to Halcon, Mr. Hartman held various positions including Assistant Controller at Petrohawk Energy Corporation from 2006 until their sale to BHP Billiton in 2012.  Prior to that he held accounting and finance positions at multiple entities and an audit position with PriceWaterhouseCoopers.  Mr. Hartman holds B.B.A. and M.S. degrees in Accounting from Texas A&M University.  Mr. Hartman is a Certified Public Accountant in the State of Texas.




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