Abstract
Gas well loadup is a very serious problem for the petroleum industry. Gas well loadup is the result of the loss of available reservoir energy due to the accumulation of liquids in the wellbore over time. In order to deal with this problem several techniques have been developed. They include plunger lift, small-ID tubing, gas lift, flow controllers, submersible pumps, sucker rods, swabbing, jetting and foaming. Among these foam lifting has been used quite successfully in the field for removing liquids from the wellbore and the annulus. However, there is a strong need for using a systematic approach in order to find out under which conditions foam lift is successful and under which conditions it is not successful. Foam lifting experiments are conducted in a specially designed 40’-long flow loop, in which foam is injected from the bottom of the tubing, which is filled with liquids. The efficiency of liquid removal for a wide range of gas and liquid flow rates is measured by comparing the liquid holdups at the end of each period of foam injection. The liquid removal efficiencies are also compared against cases in which no foam is injected (base-cases). Foam injection shows superior liquid removal efficiency compared to the base-cases. Special considerations are also given to cases in which a 50-psi backpressure is applied. Comparisons are also made between 1" and 2" tubing sizes. Results show that the type and concentration of the surfactants used to generate the foam has a strong influence on the liquid removal efficiency.
