Recyclable and Highly Inhibitive Stable Foam Drilling Fluid

Recyclable and highly inhibitive stable foam drilling fluid was researched to reduce the large amount of disposable foam and related materials and solve wellbore stability issue in foam drilling.Based on the foam circulation and shale inhibition mechanisms,the recyclable and highly inhibitive stable foam drilling fluid was developed through the performance evaluation of different chemical agents.The comprehensive performance of the foam drilling fluid was evaluated through conventional foam performance evaluation,foam circulation performance test and shale inhibition performance test.The results showed that the foam drilling fluid kept above 400 mL foam volume with the hot rolling temperature of 130 ℃,the NaCl mass fraction of 15%,cuttings content of 15% and kerosene content of 15%,indicating good temperature tolerance and contamination resistance.Through the pH adjustment,the foam drilling fluid could keep a 500 mL foam volume after the eight foam circulation.The recovery rates of the shale in the foam drilling fluid stay above 96% both in the first and second rolling recovery tests and the shale kept a great hardness that was similar to the hardness of white oil treated shale.Thus,the foam drilling fluid not only could avoid the large accumulation of foam on the ground and save drilling costs,but also could effectively prohibit clay hydration and swelling for an extended period,and consequently enhance the wellbore stability in foam drilling.