Due to the improvements in the technology of horizontal well construction, there is a tendency to extend the use of horizontal wells for improving the overall efficiency of different recovery processes, including waterflooding. Using horizontal wells in a waterflooding process, a higher sweep efficiency for less cost is expected as opposed to the use of classical patterns by vertical wells. However, the use of horizontal wells is very sensitive to the well pattern designed to operate such a process.

The paper presents an analysis of how the overall efficiency of a waterflooding process is influenced by the well pattern using horizontal wells. Three cases were taken into consideration: first for a pattern using two parallel horizontal wells, one for injection and the other for production, second for a pattern using one horizontal well for water injection and few vertical wells for production, and the third for a pattern using vertical wells for injection and one horizontal well for production.

A two phase two dimensional numerical model was used to make the simulation of the waterflooding process for each case. The results showed that the pressure loss along the horizontal section has a large influence on the sweep efficiency both for using an injection and/or a production horizontal well. Also, the results showed that it is preferable the use of vertical wells for injection and horizontal wells for production rather then the use of horizontal wells for injection and vertical wells for production.

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