Retrieved December 11, 2015. ↑ The "maximum efficient rate" is an engineering determination of the theoretical optimum rate of flow of crude oil from each well in a pool that will not endanger ultimate recovery from the pool by a too rapid release of underground pressures. MER depends on the character of the oil-bearing structure and the nature of the natural drive – whether water pressure, a gas cap, or gas in solution in the crude oil. Engineers look at indices like the pressure at the bottom of the well ("bottom-hole pressure") or the ratio of gas to oil in the crude produced.