Sean W. Marshall serves as Senior Counsel, in an Of Counsel capacity, with R. Reese & Associates, where he represents businesses in corporate transactions, mergers and acquisitions, governance, regulatory, and strategic matters. Sean brings a distinctive blend of legal insight and senior-level business leadership, having spent his career moving fluidly between law practice, executive management, capital formation, and business development roles.

In addition to his work with the firm, Sean continues to serve as President and CEO of Mestengo Energy Company, where he led the formation and capital raise of a non-operated investment fund and now oversees strategy, governance, and portfolio execution. He is also Executive Director of the Permian Summit Foundation, a charitable organization supporting abused and neglected children while serving as a premier networking and relationship platform for business leaders.

Sean’s background spans family-office enterprises, traditional private-equity platforms, founder-led ventures, and publicly traded corporations. He began his upstream career in a family-office environment at Hawkeye Oil & Gas, working across both legal and commercial responsibilities. He later served as General Counsel and Vice President of Land at Source Energy Partners, where he led and supported acquisitions, divestitures, commercial negotiations, and governance functions in a private-equity-backed environment.

Sean also held a multi-function executive role at Centennial Resource Development during its growth from a SPAC-stage enterprise into a major public company under the leadership of Mark Papa, ultimately participating in the company’s trajectory through a multi-billion-dollar strategic combination and exit. Over the course of his career, Sean has been involved in oil and gas mergers, acquisitions, estate planning, and asset sales and divestitures exceeding $5 billion in aggregate transaction value, giving him deep, practical experience structuring and executing complex deals.

He has also worked extensively in regulatory strategy, government relations, sustainability initiatives, and corporate responsibility, enabling him to advise clients with a clear view of legal exposure, stakeholder dynamics, and long-term enterprise value.

Alongside his corporate and transactional practice, Sean maintains a complementary estate-planning practice, counseling families and business owners on wealth-transfer strategy, governance structuring, and asset-protection planning.

Drawing on this breadth of perspective, Sean is well-suited to advise entrepreneurs, closely held and family-owned businesses, private-equity-backed ventures, and growth-stage companies across industries. Clients seek him out for practical, business-savvy transactional counsel grounded in real-world executive and investment experience.