Solubility Variation and Prediction Model of CO2 in Water-Bearing Crude Oil

The solubility of CO2 in water-bearing crude oil is of great significance for the calculation of crude oil reserves, the development of CO2-EOR (CO2-enhanced oil recovery), CO2-CCUS (carbon capture, utilization, and storage), and CO2 assisted steam huff-and-puff technology, and the optimization of the design of CO2 for heavy oil pipeline transportation. In order to determine the variation of the solubility of water-bearing crude oil by injecting CO2 into the formation, taking the Upper Wuerhe Formation reservoir in the 53 East Block as an example, the study of the dissolution characteristics of CO2 in water-bearing crude oil at different temperature and pressure conditions was carried out by using a high-temperature and high-pressure reaction kettle. At the same time, a new solubility prediction model of CO2 in water-bearing crude oil was proposed based on the existing solubility prediction models. The results show that, under the same water cut, the solubility of CO2 in water-bearing crude oil decreases with the increase of temperature and decreases with the decrease of pressure. At the same time, the solubility of CO2 in water-bearing crude oil is more sensitive to pressure. At the same temperature, the solubility of CO2 in water-bearing crude oil decreases with the increase of water cut, and the higher the pressure, the greater the effect of water cut on the solubility of CO2 in water-bearing crude oil. The newly established combined prediction model of CO2 solubility in water-bearing crude oil is convenient for calculation and has a wide range of applications. The average relative error is only 9.5%, which can meet the requirements of engineering calculation accuracy.