The project performer proposes final research and development in the United States to evaluate a technology that was developed at the Institute for Geology and Development of Fossil Fuels in Moscow, Russia. This technology involves in-situ generation of carbon dioxide (CO2) to recover trapped residual oil from reservoirs. In Phase I, the project performer will verify if the Russian formulations generate sufficient pressure and CO2 concentration in situ, allowing miscibility to be attained with typical oils. Phase II will evaluate how effectively the foams generated by this process improve sweep efficiency in porous rock with a range of permeabilities.

New Mexico Institute of Mining and Technology, Socorro, NM

Institute for Geology and Development of Fossil Fuels, Moscow, Russia

This new technology presents the following opportunities and challenges. Advantages include:

• Dissolution of CO2 (~5-10 %) in water results in:
  • Viscosity increase.
  • Reduction of mobility
• Dissolution of CO2 in oil results in:
  • Viscosity decrease.
  • Increase in oil recovery efficiency.
  • Reduction of surface tension between oil and water phases.
  • Increase both in oil production and sweep efficiency.

Disadvantages include:

• CO2 breakthrough in producing oil wells.
• Small alterations of thermobaric equilibrium conditions result in reducing CO2 concentration in oil and, consequently, a coagulation and deposition of asphaltenes and resins.
• Corrosion of oilfield equipment.
• Problems related to transportation of great volumes of CO2 gas.
• Special equipment required for safe storage and transportation of CO2 gas.
• High cost of the technology.
• Insufficient amount of CO2 in many oil-fields.

Previous oilfield tests include the following:

• Samotlor oilfield, Tyumen Oil Co. (Russia), involving 121 operations from 1999 to 2001.
• Novo-Pokursky oilfield, Slavneft-Megionneftegas JSC (Russia), involving 56 operations from 2000 to 2004.
• Gunyuang oilfield (China), involving 20 operations covering 45 producing oil wells.

Results 
Project highlights to date include the following:

• Two experimental devices have been designed and built for measuring the pressure and the volume of the CO2 gas generated according to the proposed new Russian technology.
• Preliminary experimental results on CO2 gas pressure measurements demonstrated that the gas pressure increases with 1) polymer/surfactant addition, 2) decreasing temperature, and 3) increasing salinity of the system.
• At certain salinity values, the generated gas pressure starts decreasing.
• An alternative “gas-yielding” reactant was proposed and tested in order to optimize the reaction process.
• Injection sequence of the gas-forming and gas-yielding materials affects the reaction characteristics, but the total amount of generated CO2 gas does not vary significantly.
• Regardless of the injected solutions, the maximum attainable pressures are less than the calculated pressures as a result of chemical equilibrium in the system.

Benefits 
The new technology offers these benefits:

• Enhanced resistance to injected water flow due to steady foamy barrier.
• Enhanced extraction of hydrocarbon components from porous media surface at certain thermobaric conditions of super-critical CO2 gas.
• Increased sweep efficiency due to in-situ generated CO2 gas.
• No need for additional pipelines and power supplies for CO2 gas injection. Applicability in severe-climate zones.

Summary 
Basic concepts of the technology entail these findings:

• The supercritical state of CO2 can be adjusted by reactions between gas-forming (GF) and gas-yielding (GY) agents under certain thermobaric conditions.
• The injected liquids will flow into the low-permeability zones due to the generated gas temporarily blocking high-permeability zones.
• Water-soluble polymers added to the injected liquids system have two functions:
  • They generate foam when it is necessary to block high-permeability intervals.
  • They provide viscoelasticity and flatten the displacement interface when reactants penetrate into the low-permeability zones, and CO2 breakthrough into the producing wells is prevented.
• Micro-bubbles generated due to the exothermal reaction possess anomalous rheological properties which, under equal circumstances, allow an increase in sweep efficiency.
• GF and GY reactants are Newtonian fluids and therefore first penetrate the high-permeability zones, where the CO2 will be generated.
• Surfactants promote hydrophobization of pores during filtration of the gas-liquid mixture into the horizons in a pre-transitive phase state and thus increase its viscoelastic non-equilibrium properties.
• The gas-liquid system increases injectivity of the injection wells.
• Surfactant additives decrease corrosion of the oilfield equipment because cationic surfactants are good inhibitors of corrosion and under subsurface conditions do not generate deposits.
• The foamy gas-liquid system in high-permeability zones creates additional resistance to the injected water flow.
• A major portion of the CO2 is used to create a barrier against flooded zones.
• Part of the CO2 dissolved in oil creates a volumetric effect and sweeps out residual oil.
• CO2 dissolved in water increases its viscosity, equalizes the displacement front, and increase sweep efficiency.

(April 2008) 
This project has been completed and the final report is listed below under "Additional Information".

$559,268 

$141,717 (20% of total)

NETL – Traci Rodosta (Traci.Rodosta@netl.doe.gov or 304-285-1345)
NMIMT – Sayavur Bakhtiyarov (sayavur@nmt.edu or 505-835-5373)

Final Project Report [PDF-3.40MB]

Publications 
S. I. Bakhtiyarov, A. K. Shakhverdiyev, G. M. Panakhov and E. M. Abbasov, 2006, “Volume and Pressure Measurements in Oil Recovery by In-Situ Gas Generation”, International Journal of Manufacturing Science and Technology (accepted).

G. M. Panakhov, A. K. Shakhverdiyev, S. I. Bakhtiyarov and E. M. Abbasov, 2006, “Kinetics of Gas-Generation Processes in Liquid Solutions”, Proceedings of 12th International Conference on Mathematics and Mechanics, Baku, Azerbaijan (accepted).

S. I. Bakhtiyarov, A. K. Shakhverdiyev, G. M. Panakhov and E. M. Abbasov, 2006, “Oil Recovery by In-Situ Gas Generation: Volume and Pressure Measurements”, ASME Joint U.S.-European Fluids Engineering Summer Meeting, Miami, FL, July 17-20, 2006, Paper # FEDSM2006-98359 (accepted).

O. Coskun, R. Grigg, R. Svec and S. I. Bakhtiyarov, 2006, “The Effect of Salinity on In-Situ Generated CO2 Gas: Simulations and Experiments”, Symposium on “Advances in Materials Processing Science”, ASME International Mechanical Engineering Congress and Exposition, Chicago, IL, November 5-10, 2006, Paper # IMECE2006-15703 (accepted).