Extended throat venturi based flow meter for optimization of oil production process

Abstract

Water is mixed with the crude oil to form complex multiphase fluid during oil extraction process. Some of the traditional methods to measure the relative amount of water mixed with the crude oil (known as water-cut or WC) are intrusive, which are prone to wear and tear. Few other methods, used for WC sensing, are either unable to cover full range (0-100% WC) or require good mixing of the production fluid to be sensed accurately. This paper presents a unique and robust design of a dual spiral microwave resonator, which has been integrated on the extended throat of a venturi. Venturi measures the flow rate of the overall fluid while the microwave resonator measures the relative fraction of water in oil. Unlike existing meters, the presented design is fully non-intrusive, covers full WC range and does not require any mixing of production fluid for accurate measurement. The meter has been designed to withstand harsh field conditions of 1000 psi pressure and 125.C temperature and its performance has been validated in a commercial industrial flow loop with variable salinity conditions. “Phase inversion” phenomenon where the mixture changes from “oil continuous” to “water continuous” or vice versa, has been characterized thoroughly under varying test conditions. Microwave sensor’s resonance frequency (fo) and quality (Q) factor are used to measure WC in oil continuous and water continuous conditions respectively. The meter has been tested over wide range of flow rates and full range (0-100%) of WC. Liquid flow rate accuracy of ±3% and water cut accuracy of ±2% has been obtained from the industrial flow loop measurements.