A novel method of simultaneously processing two sands using a single injection string (the "checkerboard" injection scheme), in which adjacent pattern injectors are completed alternately into upper and lower sands, is evaluated numerically. The new scheme is compared with two others: (1) the conventional "sequential" injection and (2) the case where steam is injected into the lower sand only and the "hot-plate"-heated upper sand is drained by gravity alone.
Results show that the checkerboard injection scheme is superior to the sequential for a constant oil and gas price scenario. It results in accelerated production and has lower completion costs. However, the sequential scheme results in the highest recovery. The checkerboard scheme may be especially useful in situations where acceleration of oil recovery may be desired or when the steam injection period may be limited by external constraints. Oil production from the heated upper sand by gravity drainage alone results in the lowest recovery and is not recommended (unless steam injection in the upper sand is uneconomic). Results also show that, for this nondipping reservoir, a significant amount oil is recovered from heated areas outside the pattern boundaries.