Chemical Tracer Application to Compare Napthalene Sulfonic Acid and Sodium Fluorobenzoic Acid as Part of Polymer Field Trial Project

Abstract

Abstract Tracer testing is the effective method to characterize subsurface, especially to investigate well connectivity or fluid pathways, estimate traveling velocity of injected fluid, assess the breakthrough times of the tracers between injectors and producers, and evaluate swept pore volume and sweep efficiency particularly in Enhanced Oil Recovery (EOR) operation. Fluoro-benzoic acid (FBA) remains the primary and most common liquid phase tracer in oil industry, but recent laboratory and geothermal field test using Naphthalene Sulfonic Acid (NSA) also looks very promising. The NSAs are thermally stable at reservoir conditions, cost about a tenth of the cost of FBAs, and have a much lower detection limit when tested using High Performance Liquid Chromatograph (HPLC). The drawback is that they have not been widely tested in oil reservoir but have proven themselves in the laboratory tests and in geothermal reservoirs. This paper describes performance test of NSA as chemical tracer in oil reservoir in direct comparison with proven conservative tracer, FBA by pairing an NSA tracer with a proven FBA tracer in the same injector well as part of IOR polymer pilot project. Six different types of NSAs were injected at the six different injection wells. In addition, six different types of FBAs were also injected at the same wells to make comparative data with NSA at producer wells. The tracer test was performed for 170 days with relatively constant injection and producing rate to maintain steady state condition in the reservoir. The injection and production rates were balanced for the test duration. Bottom-hole temperature is about 85°C.