PVT Sampling With Multiphase Flowmeters—Theoretical Justifications and Field Limitations

Abstract Multiphase flowmeter technology probably is the most significant innovation in surface well testing in more than 30 years. Multiphase flow measurement is becoming a globally accepted technique for well and reservoir performance evaluations. The qualification of the validity of samples collected during these operations is required to validate the full potential of multiphase well testing techniques. This paper discusses the new methodology developed for collection of samples using dual-energy spectral gamma ray Venturi multiphase flowmeter technology in field operations. The paper presents some of the theory and assumptions underlying multiphase flow computations and valid sample collection with the flowmeter. Field operations are detailed in the paper and provide operational guidelines to improve safety and optimize sampling operations. A description of the laboratory pressure/volume/temperature (PVT) analysis procedures required to physically recombine these nonconventional gas and oil samples is provided, and a series of field examples illustrate the efficiency of using multiphase flowmeters for well testing. A sensitivity analysis is conducted for various gas and oil sample recombinations and resulting PVT properties computed by equation of state-(EOS-) based compositional simulations. The parameters considered are possible variations in sampling temperature or pressure and their impact on the resulting recombined fluid PVT properties.