Service contracts are currently one of the most common petroleum contract models in the international arena. According to the relevant rules issued by the U.S. Securities and Exchange Commission (SEC), in a service contract, the SEC net reserves of physical oil and gas assets legally owned by the oil company are different from the operating production and the equity production, but are the share of oil and gas volumes calculated based on the cost recovery and compensation fees of the oil company. Net reserves are not only related to technical factors such as initial production, decline rate, recovery rate, and work program for the next five years, but also depend on non-technical factors such as commercial, economic, and engineering. Taking a service contract crude oil project in South America as an example, this paper analyzes the estimation method of SEC net reserves and value of oil and gas assets under the service contract model, which is helpful to meet the efficient management of oil and gas assets and the achievement of business assessment indexes of oil companies.