The start up of new wells in heavy oil and bitumen fields is an important and complex technological process. The article presents the study results of the solvent efficiency for horizontal wells’ start up procedure. There are assessments 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 separation of the process by the physical components was used to evaluate the convective-diffusion mass transfer of the solvent to improve the wells’ start up efficiency. An analytical solution of the diffusion equation was applied to calculate a diffusive mass transfer.
Noted, that there is more efficient wire wrapped screen in comparison with slotted liner for effective mass transfer of the solvent into heavy oil and bitumen. Based on the calculations by using diffusion time and a characteristic distance of the diffusion process passage have been got the volume of near-wellbore zones in horizontal wells swept by the solvents. Have been determined that the most significant decrease in specific viscosity for an estimated solvent occurs at its low concentrations in the heavy oil in the range of 0.05-0.1%.
Successful practices of solvent assisted start up through development of the heavy oil project in the Tatneft PJSC reaffirm the applicability of the performed solutions for the planning of such process including steam assisted gravity drainage (SAGD).
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