The effects of oil contamination on the stability and flow behavior of drilling foams under high-pressure conditions

Abstract

Foams used in drilling can be contaminated by formation influx containing oil. The stability and flow behavior of foam are affected when it comes into contact with oil. The objective of this study is to investigate the impact of oil on foam drainage and rheology under high-pressure conditions.Drainage and rheology experiments were performed introducing different types of oils (mineral oil, light crude oil, and heavy crude oil) into the surfactant solution at varying concentrations. The tests were performed at three different foam qualities (40%, 50% & 60%). To determine the drainage, the foam was first generated in a flow loop and its rheology was measured. Subsequently, its drainage was evaluated by trapping it in a vertical test section (stability cell) and measuring the pressure profile of the foam column trapped in the cell using ten pressure sensors. The foam drainage was determined as a function of time by analyzing the pressure profile data. Tests were conducted under ambient temperature (25 ± 3 °C).The results show how the foam drainage and rheology were affected by oil type and concentration. Low-quality foam (40%) showed a slight stabilizing effect with increasing mineral oil concentration. However, high-quality foams (50% and 60%) destabilized with increasing the concentration of the mineral oil. Crude oil type was found to affect the stability of the foams. Light crude oil had a more destabilizing effect as compared to heavy crude oil.