It is suggested that greater recovery of oil will be obtained: (1) by maintaining the pressure of the reservoir at high values, (2) by keeping gas, oil, and water segregated in their natural relation as far as possible.
To bring about these conditions, low rates of flow are essential, especially in water-drive fields. Likewise, free gas and water should not be produced. The mechanism by which gas and water enter wells may be either one of movement in mass through parts of the sand containing little or no oil, or one of movement with the oil through sands containing oil with water or free gas. Production of gas or water by the first method can often be prevented by repair of the well, whereas little can be done to control these fluids if the second mechanism is responsible for their production. As high rates of flow tend to bring about commingling of free gas and water with the oil, they may cause a premature development of high gas-oil or water-oil ratios.
Completion of wells should be given careful attention, and completion and repair operations should be governed by the structure of the reservoir and the condition and nature of the fluids therein. Proper consideration of these factors will result in more successful operations and in greater oil recovery from a field.