Development and Application of New Multifunctional Foaming Agents to Enhance Production in Oil Wells

Abstract

Summary Maintaining or increasing production from wells in mature oil reservoirs with high pressure, temperature, brine hardness, and salinity is a significant technological and economic challenge. These wells usually produce with a high gas-oil ratio and large water cuts and often operate with gas lift systems. This work focuses on the development and application of new multifunctional foaming agents (MFAs) to enhance production from oil wells under these conditions. The MFAs were developed based on molecular design and laboratory studies, which demonstrated that they can be used with water cuts exceeding 30% and in the presence of salinity and hardness levels up to 400,000 ppm and 180,000 ppm, respectively. Furthermore, these agents remain stable at temperatures up to 180°C. The production/lift efficiency of the MFAs was evaluated using two novel dynamic laboratory methods that are conducted close to the wellhead and at downhole conditions of temperature and pressure, respectively. The experimental results demonstrate a significant enhancement in the liquid production efficiency, with some cases showing an increase from no production to as much as 44% when the MFAs were used. The laboratory tests were also used to optimize the MFA type and concentration in the design of a field application. The field test was conducted in three oil wells with water cuts ranging from 40% to 90%, depths exceeding 5000 m, bottomhole temperature around 150°C, and brine hardness and salinity up to 180,000 ppm and 310,000 ppm, respectively. This is the first reported field test of MFAs for production enhancement under such challenging conditions. The MFA was coinjected with gas lift via the annulus. The MFA mixed with reservoir fluids in the tubing and generated foam downhole with concentrations ranging from 160 ppm to 750 ppm. The rheological properties of the foam were designed to prevent pressure losses and the formation of stable foam or emulsions at surface facilities. The field tests demonstrated that the MFA was able to increase oil production at a fixed gas lift injection flow rate. Alternatively, it was able to reduce lift gas consumption while maintaining or even increasing the original oil production.