Calculation of sweep efficiency for water flooding development of conventional heavy oil using the stream-tube method

In terms of the characteristics of pattern flooding of conventional heavy oil reservoirs, to eliminate the problems related to water-flooding plane, stream-tube method has been used to develop equations for calculation of sweep efficiency, timing and watercut on unit area of flooding operations. These newly developed equations have been applied successfully in inverse 9-point pattern successfully for the first time to calculate areal sweep efficiency under two-phase flooding theoretically. Research results show producers for heavy oil development may have quickly increasing watercut and rapidly decreasing areal sweep efficiency after water breakthrough. Since wells on the boundary or corners of the inverse 9-point pattern may have different water breakthrough time and areal sweep efficiencies, different flooding systems shall be deployed to achieve more evenly distributed water-flooding performances. Theoretical calculation results are consistent with numerical simulation conclusions. The innovative calculation methods may provide reliable theoretical foundation for future studies for areal sweep efficiency.