Netherland, Sewell & Associates, Inc. (NSAI) is an upstream petroleum consultancy founded in 1961 and based in Dallas, Texas, with a second office in Houston. It prepares reserves certifications, technical studies, economic evaluations and advisory work for onshore and offshore fields, and states that it has carried out assignments in more than 100 countries. The firm's about page lists more than 55 engineers, geologists, geophysicists and petrophysicists together with over 70 engineering and geology analysts, and Richard B. Talley, Jr. is chairman and chief executive.
Reserves reporting and asset evaluations
Independent reserves work is the firm's core business. NSAI prepares SEC reserves reports and audits — stating that more companies choose it for SEC reserves reporting than any other petroleum consultancy — along with competent person's reports, acquisition and divestiture evaluations in which engineers and geologists attend data rooms and run independent analyses, equity determinations, project finance certifications, prospective resources assessments and litigation support in disputes. Unconventional oil and gas evaluations cover all the major North American plays and emerging plays elsewhere, with insights delivered at lease, local and regional level for clients from small independent operators to national oil companies.
Technical disciplines
Work is organised into four discipline groups: reservoir engineering, geological and geophysical services, petrophysical consulting services, and economic analysis.
- Reservoir engineering and simulation, including enhanced recovery projects.
- Operations engineering services and midstream consulting.
- Coal seam gas development studies; the firm says it has worked every major producing CSG/CBM basin in the world and runs training classes on the subject.
- Deepwater development studies and gas storage studies.
- Helium resource evaluations.
Energy transition services
A sustainability practice sits alongside the upstream work. NSAI certifies carbon capture, utilisation and storage projects, covering storage capacity assessment, modelling of CO2 storage processes and economic modelling to quantify project value, whether injection is planned into hydrocarbon-bearing formations or aquifers. Related offerings include greenhouse gas management and carbon intensity studies, and separate CCS seminars are advertised in addition to the firm's main seminar programme.
Resources and client base
Beyond project work, NSAI publishes pricing data and guidance on calculating differentials, with an email list for pricing updates. Its stated experience covers carbonate and clastic producing basins worldwide, spanning terrestrial, deltaic and deepwater depositional settings, and it reports having delivered thousands of reports for petroleum companies and financial institutions. Assignments range from small single properties to large integrated development projects, and the firm also provides litigation support and dispute resolution services.
The Netherland Sewell School
NSAI runs an Oil & Gas Property Evaluation Seminar, commonly called the Netherland Sewell School, for non-technical financial professionals whose work relates to the petroleum industry. Session topics range from basic reserves determination methods and economics to petroleum geology, with special-interest topics such as CCUS, and attendance is free. The 2026 programme lists a two-day seminar in Dallas on 12-13 May 2026 and a one-day seminar in Houston on 21 July 2026, with further one-day sessions advertised for Salvador in Brazil, Cape Town, London, New Delhi and Singapore, and a Spanish-language session in Mexico City whose date was still to be defined at the time of checking.
History, offices and contact
Clarence Netherland started the firm on his own in 1961 after deciding it would be the leading organisation of its kind, hiring each employee personally. Fred Sewell joined in 1969, when the business had fewer than six employees, bringing commercial experience to the technical practice, and the Houston office was added in the early 1990s. Clients are drawn from the petroleum industry, financial institutions and government agencies, and the firm publishes pricing data and differential calculation resources alongside its client work. General enquiries for both offices use [email protected], while seminar registration uses [email protected].