Experience and Qualifications that Produce Sustainable Results


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Our Leadership

Mr. Guillarmo (Gil) Marmol is a Senior Director with The Quaker Group based in Dallas, Texas. Gill was a McKinsey & Co. Director (Senior Partner) that worked in the Chicago and Mexico City Offices before moving to Dallas in 1983. Gil specializes in performance improvement in the oil and gas and chemicals industries. 

Gil was a leader in McKinsey's organization and business process redesign practice areas. Over a five-year period, Gil advised a leading energy company in establishing a leadership position in two of the largest US energy markets. Gil led McKinsey's organization and business process redesign practices. Gil also completed a study of high performing organizations that was reported in the Wall Street Journal and underpins McKinsey's organizational work around the world. 

Gil has an MBA, with Distinction, from the Harvard Business School and a BS, Magna Cum Laude, in Engineering and Applied Physics from Harvard College. Gil is fluent in Spanish. 

Dr. Andy Callegari is a Senior Director in the Energy practice of The Quaker Group and is based in the Washington, DC area. Andy has 27 years of ExxonMobil experience as a technology leader in Research and Engineering. Andy also has 9 years of experience as a management consultant serving global energy companies (NOCs, IOCs & INOCs), as well as related services, legal and financial clients.


As a manager with ExxonMobil Andy has developed strategies aligned with key business drivers. Andy has managed the development and deployment of a wide range of technologies leading to competitive advantage at ExxonMobil. Andy has led divisions of up to 150 engineers & scientists.


Specific examples of Andy’s experience as a leader for major multi-year initiatives at ExxonMobil Corporation include:

- Implementation of Global Systems for Energy Management (GEMS)

- A Global Reliability and Maintenance program for upstream, downstream and chemicals

- Providing R&D and technology management in a global margin improvement program involving the industry leading molecule management initiative (MMP)


Prior to joining ExxonMobil Andy held several academic positions in Applied Mathematics and Applied Science at New York University in New York City and the State University of New York. Andy was also a Visiting Professor of Mathematics at Oxford University, UK. Prior to Andy’s 27-year Exxon career he was a consultant to the US Navy, NASA and the US Department of Energy. Andy holds a BS., MS, PhD – Applied Mechanics & Mathematics from Columbia University.

Mr. Larry Lester is a Partner in the Energy Practice of The Quaker Group based in Houston, Texas. Larry specializes in Maintenance Improvement strategies and Organizational Leadership concepts. He is also experienced in the area of Engineering and Project Management. Larry has more than 30 years of experience working as an Engineer, Supervisor, Manager, and Maintenance Advisor for ExxonMobil Refining and Chemical operating units. 

Larry worked as an ExxonMobil Work Management Second Level Manager and Site Advisor. Larry has also led a team to write ExxonMobil worldwide refinery and chemical plant maintenance best practices for:

+ Planning, Scheduling and Executing day-to-day routine maintenance jobs
Member and Leader of ExxonMobil North and South America Work Management Network
+ Wrote, sponsored and implemented more than least 15 Best Practices to improve Planning, Scheduling, and Execution for ExxonMobil's upstream, downstream and chemicals divisions.

Larry has a Master of Science degree in Electrical Engineering from Stanford University. Larry also has a Bachelor of Science Degree from Prairie View A&M University with Highest Honors in Electrical Engineering. 

Dr. Russell Brown, a Quaker Group Principal, has over 25 years of engineering and consulting experience in the global downstream petroleum industry. Most of Russell’s work has been in the refining sector where he has delivered industry-leading engineering and related consulting services to increase business performance.


Russell has worked at all levels within international oil companies (IOCs), national oil companies (NOCs) and international national oil companies (INOCs) for clients in North America, Europe, Russia, and Africa. Early in his career, Russell worked for Conoco Inc., where he supported the catalytic refining units in the areas of research, development, and optimization.


Some examples of Russell’s accomplishments include:


  • Developed a successful neural-network based advanced control system for polymer processes and other applications
  • Co-author of a patented process for comparison of control systems performance, including new tools and procedures for project management and resource planning.
  • Delivered several papers and presentations, including the Solomon Fuels Study presentation.
  • Managed a project to improve performance in a refinery in western Europe. The project returned a 40% margin where over $40 million of opportunities were identified.
  • Invented a new control system for minimizing NOx emissions from a coal-fired power plant, while simultaneously controlling reheat temperature and CO emissions. The application was used for 18 years and saved the power plant millions of dollars in NOx credits and coal cost.
  • Developed and implemented a naphtha segregation scheme in a sour-crude refinery that improved throughput and yield for a CCR reformer. This resulted in a net earnings increase of $2,000,000 per year from higher reformate and hydrogen yield.

Russell obtained his B.S., M.S., and Ph.D. in chemical engineering from The Texas A&M University in College Station, Texas. Russell has also published multiple journal articles, including more recent posts in a Russian journal.

Mr. Robert (Bob) Snell specializes in operations, organization, and competitive analysis in the petroleum industry vertical. He brings more than 30 years of experience in the global energy industry with over 20 years of consulting experience involving more than 100 energy clients in over 20 countries.

Bob is the founding Partner of The Quaker Group. Bob began his management consulting career at Arthur D. Little in Cambridge, Massachusetts. Earlier in his career, Bob held various positions at ExxonMobil Corporation in refining and marketing; including line management positions in operations support, economics and planning, sales & marketing, and project engineering.

Bob helps clients across a broad set of business issues in the industry vertical including; market assessments, supply chain optimization, process operations & reliability, mergers and acquisitions, organization restructuring, strategic and business planning, and litigation support and due diligence.

Bob holds a BS in Chemical Engineering from Northeastern University, an MBA from the Wharton School of Business, and a JD from Concord Law School. Bob attended the Roxbury Latin School in Boston. Bob currently resides with his family in The Woodlands, Texas.