Aiming at the bad stability performance of normal foam in the Yan Chang No.6 oil field, a high stability gel foam system was developed and then evaluated in the aspect of stability and plugging. Through comparison and selection, now the system is made up of 0.4% FP388 foam agent, 0.3% AZ polymer, 0.3% T1&T2 crosslinker, and 0.3% CK2 foam stabilizer. The stability experiment of gel foam indicate that the half life of gel foam is 12 d and the viscosity of gel foam can stay at a high level, also remains stable in 30 d under 80 ℃ and 10 000 mg/L mineralization degree environmental conditions. The foam gel system has good injection and gel forming properties and can effectively seal medium high permeability reservoir.

The calculation and analysis for extruded reducing tees subjected to internal pressure were carried out using ANSYS software．The stress distributions law about the tee were obtained， and verified in combination with the corresponding references．The results show that the fillet radiuses have apparent effects on the tee strength ．A high stress concentration crops up in the corner，and a quadratic curve relation between the maximum stress and inner radius appears when the outer radius was given． Based on the results and related documents， empirical correlation for calculating the maximum stress of the extruded tee is put forward ．