The objective of this project is to gain a better understanding of the methods of upgrading heavy through the use of solvents, such as vaporized propane, and development of a reservoir simulator to predict the behavior of a heavy crude oil reservoir subjected to cyclic solvent injection.
Florida International University, Miami, FL
University of Texas at Austin, Bureau of Economic Geology
Production of heavy crude oil is only a small fraction of total crude production despite its overwhelming abundance. Additionally, heavy oil is usually in oversupply because of the processing bottleneck that exists at refineries due to tighter fuel standards. Recently, as the volume of sweet light crude has declined, there has been an increase in crude imports to the United States. These on average have been heavier and more sour. The two most important problems of heavy crude are the need for extensive processing and the low reservoir recovery factors. Historically, the dominant recovery process for heavy oil reservoirs is based on steam injection, either cyclic steam stimulation or a steam drive. Recovery efficiency is often limited by early steam breakthrough due to channeling through high-permeability channels, bypassing considerable amounts of oil.
Solvents and diluents have been successfully used to reduce the viscosity of reservoir fluids and increase net production. A partially miscible solvent is injected into a reservoir, and the well is then put into production. The solvent should extract the lighter fractions of the crude (those that are miscible), leaving behind the heavier, less mobile fractions. Given typical reservoir temperatures, the heavy (precipitated) fraction is still mobile, in most cases, thus avoiding formation damage. The result is a process that can upgrade heavy crude (or bitumen from oil sands), leaving heavy metals and other unwanted elements in the reservoir.
In this project an analytical reservoir model will be developed for an enhanced oil recovery process consisting of the injection of semi-miscible solvents utilized for in-situ upgrading of heavy crude oils. The model will improve the predictive capability of a reservoir simulator to capture the dynamics of solvents and heavy crude and their interaction so as to predict the production of upgraded crude oil. The reservoir simulator will be used to predict the behavior of a heavy crude oil reservoir subjected to cyclic solvent injection and when added to models of production facilities, the economics of the application to the resulting technology.
Upon completion of this project, the research results should indicate the potential to recover significant amounts of heavy oil by injecting semi-miscible solvents, such as propane, into the reservoir for in-situ upgrading of the crude oil. In addition to numerical models for the upgrading processes, this effort will provide knowledge of the flow of the injected fluids and of the upgraded crude and changes in reservoir properties after the upgrading process, and should serve to optimize future well architecture and construction.
A predictive model has been developed that assesses the near well behavior of supercritical CO2 and its interaction with heavy crude oil. The model accounts for the density of supercritical CO2 which is highly pressure sensitive and thus its capacity to precipitate asphaltenes will change. The model, which simulates mass dispersion and concentration of the gas into the oil or bitumen, assumes a cylindrically shaped well. A simulation of the diffusion process within the periphery of the injection well is depicted in the figure below. An experimental setup utilizing Particle Image Velocimetry (PIV) has been developed to investigate gas diffusion in a porous media under various conditions including temperature, pressure, and viscosity. The results of the experiments will be compared to model predictions.
In conjunction with the model development activities at FIU, the University of Texas at Austin, Bureau of Economic Geology has conducted economic evaluation of the solvent-based injection processes taking into account the quality of the produced oils and further upgrading requirements. In situ solvent-based injection processes have the capacity to remove asphaltenes and some heavy metal contaminants thus reducing downstream upgrading requirements.
The project is complete and the final technical report is listed below under "Additional Information".
Special Topical Report – Advances in Heavy Oil Recovery [PDF 200KB] July 2007
Final Technical Report [PDF-1.24MB] July 2009