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Yang P.,Engineering Research Institute of NGPC Greatwall Drilling Company | Li J.,Petrochina | Sun Y.,Engineering Research Institute of NGPC Greatwall Drilling Company | Guan J.,Engineering Research Institute of NGPC Greatwall Drilling Company | And 2 more authors.
Natural Gas Industry | Year: 2014

A technical study was conducted on the basis of shale gas accumulation characteristics for an oil-based circulating micro-foam drilling fluid against lost circulation and borehole collapse caused by shale hydrous disintegration during drilling operation. Main agents including foaming agent and foam stabilizer applicable to an oil-based drilling fluid were optimally selected according to experimental results, and then its formula was developed and the associated experiments were also conducted to assess foaming volume, half-life period, rheological property, temperature resistance, contamination resistance, collapse prevention, plugging performance, and other properties. The experimental results showed that this developed oil-based circulating micro-foam drilling fluid has adjustable density from 0.65 to 0.88 g/cm3, sound rheological property, excellent temperature resistance (maximally against 150°C), and long settling time (up to 60 hours). Moreover, this drilling fluid is also featured by a strong lubrication performance, a better resistance to water and calcium pollution, a strong lost-circulation control capability, a high collapse-prevention capability, and an outstanding reservoir-protection effect. Finally, the prospect of this new drilling fluid was discussed: it can be used not only in the drilling of shale gas wells but also of wells in low-pressure and low-permeability reservoirs and evaporite beds. All in all, the drilling fluid has a sound prospect of application. Source

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