Experiment Study of Non-Equilibrium Phase Behavior and Effect of External Vibration on Heavy Oil Production

Abstract

In this thesis, two types of heavy oil experiments were explored to study the heavy oil non-equilibrium phase behavior and the influence of external vibration on heavy oil production performance. The first experiment was to use a Constant Composition Expansion and Compression (CCEC) tests to determine the pseudo-bubble point pressure at low (T = 15°C) and high (T = 75°C) temperature environment with three different volume change rates (“Fast Rate” 1.5 cm3/min; “Moderate Rate” 0.015 cm3/min; and “Slow Rate” 0.0003 cm3/min) and three different live heavy oil samples (15 mol% C2H6 + 85 mol% STO; 35 mol% C2H6 + 65 mol% STO; 55 mol% C2H6 + 45 mol% STO). The live oil samples were recombined with ethane and crude oil at the gas-oil ratio (GOR) of 8.63 cm3/cm3, 24.22 cm3/cm3; and 55.03 cm3/cm3, respectively. Then the live oil densities and viscosities of the homogenized mixing fluid were measured at different temperatures and pressures. The factors that affect the pseudo bubble point pressure of the live oil samples were examined, and it was found that high temperature, high gas concentration and low volume expansion rate resulted higher pseudo bubble point pressure. Also, the ethane-heavy oil samples were compared with the methane-heavy oil sample with the same GOR, and the latter had higher pseudo bubble point pressure than the former. The second experiment was to study the external vibration effect on heavy oil production. The external Vibration-Stimulated Gas Pressure Cycling (VS-GPC) processes with different vibration durations and frequencies were performed. The enhanced heavy oil recovery processes were compared in terms of the heavy oil recovery factor (RF), instantaneous gas production (iGP), production pressure (Pprod) and the production time of each cycle for all tests. The laboratory tests were conducted by using a cylindrical sandpacked physical model and the tests include one Gas Pressure Cycling (GPC) process, one GPC process with pre-vibration stimulation, three VS-GPC processes with 23.5-hour vibration at the same vibration frequencies, and three VS-GPC processes with 0.5-hour vibration at different vibration frequencies. The results demonstrated that the differences caused by vibration time (23.5 hrs vs. 0.5 hour) are marginal, and 2 Hz is the optimal frequency compared with 5 Hz and 20 Hz tests for this study. The heavy oil RFs for various VS-GPC process were ranked as follow: 2 Hz 0.5-hour VS-GPC > 5 Hz 23.5-hour VSGPC > 5 Hz 0.5-hour VS-GPC > 20 Hz 0.5-hour VS-GPC > pre-vibration GPC > GPC.