A respected name in its field, Collarini has been providing upstream consulting services since 1985.  Founded by engineers with major oil and gas company experience, the firm's specialties include reservoir engineering, geoscience, land administration and management, asset development, acquisition evaluation, divestment support, data management, reserve appraisal, and producing asset optimization.


With one of the largest networks of subject matter experts in the industry and a strong leadership background in oil and gas, Collarini has the ability to select the right members for your team.


We help achieve goals, improve asset performance, and are confident in our ability to find solutions to your complex and dynamic challenges.




Cheryl Collarini is a licensed petroleum engineer, specializing in reservoir evaluation, who heads three companies in the energy sector, including Collarini Energy Experts who provide specialized project management and consulting services covering the entire spectrum of upstream oil and gas activities.  Born in New Orleans, she earned a bachelor’s degree in civil engineering from M.I.T. and an MBA from the University of New Orleans.  Cheryl began her career as a reservoir engineer and supervisor at Mobil Oil, who tapped her to teach Petroleum Investment Decisions which she continued to author and instruct for over 20 years. In 1985, she left Mobil to form Collarini Engineering, a reserve appraisal firm.  In 2003, she accepted a partnership with Explore Enterprises as VP of Engineering and, in 2008, she launched Etroa Resources, where she served as CEO.  Cheryl is a member of many professional organizations, including the Society of Petroleum Engineers, the Society of Women Engineers, and the Houston Producers’ Forum. She is also a member of the Advisory Board of the University of Houston’s Petroleum Engineering Department.



Mitch Reece joined Collarini on October 1, 2002 as an Engineering Manager responsible for the Houston technical organization.  Prior to joining Collarini, Mitch was an independent consultant for Ryder Scott Co., Collarini Engineering, and an International Engineering Manager for Devon Energy. From 1982 to 2000, he held various domestic and international engineering and operations positions for Santa Fe Snyder Corporation and its predecessor, Santa Fe Energy Resources, Inc.  Mitch has direct experience in production engineering, reservoir engineering, acquisitions and divestments, field operations, and management of all of those functions.  He began his career with Tenneco Oil Company in Lafayette, Louisiana after graduating from Texas A&M in 1979 with a B.S. in Petroleum Engineering. Mitch is a registered Professional Engineer in the state of Texas and a member of the Society of Petroleum Evaluation Engineers (SPEE), Society of Petroleum Engineers (SPE), and the American Petroleum Institute ( API ).



Volker Rathmann brings 30 years of business and industry expertise to Collarini Energy Experts. His experience has been focused in leadership roles for internationally oriented and growth-potential companies. Volker joined Collarini in 2001 as Vice President of Business Development with the objective of bringing the companies to their next level of excellence. Through a series of marketing, sales, and business development campaigns, he leads a continually growing E&P staffing business in addition to managing the marketing of the collected expertise of the Collarini companies. Prior to joining Collarini, Volker held the position of Chief Financial Officer for INTEC Engineering, a provider of specialized engineering services in global frontier and deep-water projects. Before INTEC Engineering, Volker held a number of leading positions in operations, marketing, and finance within the DaimlerChrysler Corporation. During his tenure with DaimlerChrysler, he gained the experience and background of managing globally-oriented and growing firms. Volker earned a Bachelor's degree in business administration in Berlin, Germany.