Effects of Rate of Production and Producing Equipment upon Gas-oil Ratios

Studies of the forces and conditions governing the recovery of petroleumfrom natural reservoirs indicate that a low gas-oil ratio increases ultimaterecovery, retards the encroachment of water and tends to reduce lifting costs. Methods for controlling and reducing gas-oil ratios in producing wellsconsequently have been given considerable attention during the past fewyears. However, during this same period, the production from wells in nearly allfields has been fixed by proration agreements and it is the opinion of thewriter that where a well is required to produce steadily at a predeterminedrate, less than its "potential" or maximum capacity, the gas-oil ratiowill depend only upon the rate of production, and will be independent of themethod of production and of the design of equipment in the well. If no changein the rate of production is contemplated, efforts directed to improving thegas-oil ratio by altering the diameter of the flow string, changing theposition of the choke, assisting the flow with gas-lift or pump, etc., will beunsuccessful. This viewpoint is not new. It was presented by H. N. Marsh and B. H. Robinsonin 1929, but it has not been generally accepted. Although engineers believethat the rate of withdrawal and not the equipment used governs the water-oilratio, a similar opinion regarding the gas-oil ratio is not so commonlyadmitted. The rates of flow of oil and gas into the base of an oil well depend upon thefollowing conditions:The characteristics of the oil and gas.The characteristics of the underground reservoir.Temperature and pressure conditions in the reservoir.The back-pressure held against the face of the sand. In operating a well, the only one of these conditions over which control may beexercised through operating procedure and the use of equipment above the sandis the back-pressure at the face of the sand.