Abstract: Fluid potential analysis system (FPAS) is used here to study the distribution character of underground fluid potential and pressure, which can get over the limitation of imperfect drilling data to effectively predict and evaluate oil and gas resources. The application of this system has been proved successful in the east Nanhai Field. Fluid in formation is controlled under the two fluid system-compaction fluid and gravity fluid. After comprehensive analysis, we can find the most prospective formation for exploration.