Formulation of High Temperature Foaming Drilling Fluid and Performance Evaluation

As well depth is becoming deeper, high temperature stability of foam mud becomes one of the restricting factors to foam drilling. Synergistic effect between different types of surfactants can be used to enhance the high temperature stability of foams. In our study six kinds of surfactants at the optimum concentration of 0.6% have been chosen to formulate a foam. Among these six surfactants, four of them have better foaming performance, and were evaluated for their ability to resist salt contamination and high temperature stability. The evaluation results showed that dodecyl dimethyl ammonium oxide (OA) had a stable foam comprehensive value at varied salt concentration, indicating that OA has good salt contamination resistance. At 100 ℃ or above, the α-sodium olefinsulfonate (AOS) had high foam comprehensive value, indicating that AOS has better high temperature stability. Study on the compounding of OA and AOS showed that the optimum ratio of the two was AOS：OA = 4：1. The optimum concentration of the compounded AOS and OA was 0.4%. Evaluation test on a BZY-1 surface tensiometer showed that the surface tension of the compounded surfactants is decreasing with temperature, indicating that when temperature is increasing, the foam fluid formulated with the compounded surfactants is becoming more and more stable. It was found in the evaluation test that the synergistic effect of the different surfactants reaches maximum at 150 ℃, and the foam comprehensive value at 100 ℃ reached 21.96×10⁴ mL·s, indicating that the compounded surfactants have good high temperature stability.