Optimal well spacing is determined from reservoir engineering and economic considerations.

In vertical floods the approach would be to use the minimum number of injection and production wells that would permit handling the necessary volumes of fluids and at the same time minimize coning and sandwich losses.

In horizontal floods, the distance from the injection to production wells is an important consideration. The greater this distance, the longer will be the mixing length between the CO₂ solvent and the reservoir oil, which increases the CO₂ requirements (IOCC, 1993). Note that where new wells are difficult or expensive to drill and complete, small well spacings would be hard to justify without favourable incentives.