Effect of the Gas-lift on the Physical Properties of Oil

Abstract

Petroleum producers in the Mid-Continent field, up to the present time, havebeen more concerned with the mechanical operation and efficiency of thegas-lift than with its possible effects on the physical properties of the oil.As a result few specific data are available on the subject and contradictoryopinions exist. Some operators are positive that the gravity of the oil isdecreased, while others present data which definitely show that the gravity ofthe oil is increased. In other localities, some operators have given carefulattention to the effect of the gas-lift on the gravity of the oil. When theemulsions formed have given much trouble, the problem has usually been dodgedby placing the well on the pump. Certain Fundamentals Certain fundamental results may be expected under ordinary conditions andwith all types of crude oil, when gas is the prime mover of oil in producingformations. For example, the gravity of oil will decrease as the rock pressurein the producing formation declines, the change being greater in the highergravity oils. Furthermore, the character of emulsion formed is primarily dependent on thekind of oil, thus more refractory emulsions are formed from asphaltic-baseoils, less refractory from mixed-base oils, and the least refractory fromparaffin-base oils. However, refractory emulsions are sometimes formed fromparaffin or mixed-base oils that are difficult to treat by ordinary methods, especially by electrolytic processes. With oils having the same base, those oflighter gravity are less subject to the formation of emulsions, especially ofrefractory emulsions. There are two types of emulsions formed; namely, water-in-oil emulsions andoil-in-water emulsions. The former are the more common; in fact, very fewexamples of oil-in-water emulsions have been noted in the oil fields. Theamount of water produced with the oil influences the percentage of emulsionformed. Agitation and velocity of flow play an important part in the forming ofemulsions.