Research On Drilling Fluid System For Aerated

Field tests of Underbalanced drilling have been carried out in Daqing oilfield. Technical experience and economic benefit have been obtained. But the application of underbalanced drilling is restricted in four aspects: First, underbalanced drilling is difficult to be accomplished for the formation whose pressure coefficient is less than 1 g/cm3. Secondly, the cost of oil in water drilling fluid is very high. Thirdly, the drilling speed couldn't be increased greatly. Fourthly, it is difficult to deaerate for oil in water drilling fluid. In order to resolve these problems, it is sure to carry out the research on aerated underbalanced drilling technology with water base drilling fluid. A set of drilling Fluid System for Aerated Drilling have been formed. The underbalanced drilling technologies have been further developed in Daqing oilfield.By researching on the experimental evaluation on the inhibition, high temperature resistance and the properties of PVT at HTHP of aerated drilling fluid; studying on the effects of temperature on the density of aerated drilling fluid, the effects of pressure and gas liquid ratio on the properties of PVT; By the experimental study on aeration and deaeration at HTHP and the cutting carrying capacity. The water base complex aluminium polymer drilling fluid system with relatively high temperature resistance has been developed. The system is easy to be aerated and deaerated and has better rejection capability. The density of aerated drilling fluid at HTHP has been studied. The study results show the range of density of aerated drilling fluid is from 0.75 to 0.90g/cm3 for field application and can meet the requirements of the exploration and development of deep formation in Daqing. The base fluid has stronger cutting carrying capacity and can meet the need of underbalanced drilling in deep zones.