Assessment of the Solvent Preinjection Impact on SAGD well start up parameters
The article presents the results of a study of the solvent efficiency for start up of the steam assisted gravity drainage (SAGD) wells. There are results of an assessment of heavy oil/solvent mixture viscosity at their various concentrations based on the convection and diffusion processes of the mass transfer for the conditions that are typical for Ashalchinskoye heavy oil field development. The experimental data on a viscosity versus temperature dependence have been used. In addition, the developed methodology and the calculations are used for the comparative efficiency evaluation of various concentrations and different solvents for viscosity reduction of oil while start up of SAGD wells. The method has been tested when 2 different solvents were compared. Have been determined that the most significant decrease in specific viscosity for an estimated solvent occurs at low concentrations in the 0.05-0.1%. It is shown that taking into account diffusion time and a characteristic distance of the passage of diffusion processes technologically efficient concentration discussed in the article of solvents can take 0.01 to 0.02 pore volume swept by injected solvent. It is achievable in field conditions by injection of a solvent in one or two production casing volume of the horizontal well.