In the process of natural energy depletion, foamy oil is characterized of high oil viscosity, low production GOR, high daily production rate; relatively slow production decline rate and high primary recovery factor (compared with conventional heavy oil). The stability of the foam becomes the dominant factor that determines the life of the 'foamy oil'. To quantify the main factors affecting the stability of the foam, a high-temperature-high-pressure (HTHP) visualized experiment model for foamy oil stability test was developed. A serial of experiments were conducted to evaluate the performance of the foam stability under different conditions, including temperature, dissolved gas oil ratio, pressure decline rate and the pore sizes. As indicated by the test results, the stable foamy oil exists only if the reservoir temperature is lower than 70 degrees C. The initial dissolved gas oil ratio was higher than 4.23 m(3)/m(3) and the pressure depletion rate was higher than 0.0018 MPa/min. It was also concluded that as the pore sizes of the porous media becomes closer to the actual reservoir pore size, the foam can last longer, which indicates that the "foamy oil" will exist for a long time during the reservoir development. The experimental results above have been used to guide the development of Block MPE-3 in Venezuela. (C) 2013 Elsevier Ltd. All rights reserved.