Relative Permeability of Foamy Oil for Different Types of Dissolved Gases

Abstract

Summary Foamy-oil flow is encountered not only during the primary stage of the cold-heavy-oil-production (CHOP) process through evolving methane originally in the oil but also in the post-CHOP enhanced-oil-recovery (EOR) applications in which different gases are injected and dissolved in heavy oil. Despite remarkable efforts on the physics of foamy oil flow, the mechanics of its flow through porous media is not properly understood yet. This is mainly because of lack of detailed experimental studies at the core scale to clarify the physics of the process and to support numerical-modeling studies. One also should test foamy-oil flow for different types of EOR gases dissolved and evolved at different conditions under pressure depletion. The objective of the present work is to perform detailed laboratory experiments on foamy-oil flow through porous media. Pressure/volume/temperature (PVT) studies were conducted to determine the actual pressure ranges in the coreflooding experiments in the beginning. After dissolving different gases in dead oil at 400 psi for methane (CH4) and carbon dioxide (CO2) and 112 psi for propane, the oil was injected into a sandpack to saturate it. The solution-gas-drive test was started by opening the outlet valve of the coreholder after reaching equilibrium. To mimic typical post-CHOP EOR conditions with methane, propane, or CO2 injection, the pressure was kept high (400 psi for CO2 and CH4 and 112 psi for propane). The produced oil by solution-gas drive and the gas evolved were monitored by collecting them in a graduated cylinder and a gas cylinder, respectively, while the pressure was recorded by an automatic data-acquisition system. The experimental data provided information about the effect of initial pressure of the depletion test in the amount of oil and gas measured as well as the visual observations of bubble characteristics of the foamy oil. Results showed that, among the three gases, CO2 is a good candidate for foamy oil. Maximum oil recovery [more than 50% of original oil in place (OIP) (OOIP)] was obtained in case of CO2.