An extensive experimental study was performed to investigate the effect of various parameters such as temperature, pressure, and crude oil API gravity on the fluid interactions in the binary systems of brine-CO2 and two heavy oil-CO2 systems. The solubility of CO2 in 20 000 ppm brine solution was measured at various experimental conditions. The solubility of CO2 and swelling factor, due to the CO2 dissolution, of two heavy crude oil samples (type-I: degrees API = 20.44 and type-II: degrees API = 15.49) were experimentally measured at various operating conditions. Results showed that the solubility of CO2 in heavy oil increased when the experimental pressure increased, and when the experimental temperature decreased. At a constant pressure of P-exp = 3.44 MPa, the solubility of the CO2 was measured to be 10.13, 5.72 g CO2/100 g oil in the type-I crude oil when the temperature increased from T = 21 to 45 degrees C. Increasing the experimental pressure from P-exp = 1.38 MPa to 3.44 MPa at a constant temperature of T = 21 degrees C increased the solubility of the CO2 from 2.37 to 7.84 g CO2/100 g oil in the type-II crude oil. The reduction in the oil API gravity had an adverse effect on the CO2 solubility. At a temperature of T = 21 degrees C and a pressure of P-exp = 3.44 MPa, the CO2 solubility decreased from similar to 10.13 in the type-I oil to 7.84 g CO2/100 g oil in the type-II oil. The measured values of the swelling factor showed that the type-I and type-II crude oils could exhibit a maximum swelling factor of 1.079 and 1.052 at a temperature of T = 21 degrees C and a pressure of P-exp = 3.44 MPa.