Laboratory Investigation on Recyclable Micro-foam Drilling Fluid

The M.I.S oilfield(Iran) is an old oilfield developed for more than 100 years.The lowest formation pressure is only 0.38~0.42 MPa/100m.The drilling fluid for horizontal well must meet drilling fluid loss control,hole cleaning and reservoir protection.According to agitation method,on the basis of foaming agent and foaming stabilizer,formula of foam drilling fluid was optimized,i.e.water+0.2% Na2CO3+0.1%sulphur remover +1%~2% bentonite+0.3%forming agent+ 0.4%foaming stabilizer.Test results show that foam drilling fluid has good stability,good suspension ability,good plugging property,anti-expansion and anti-contamination.Influencing factors of foam drilling fluid on density are temperature and pressure.