Research On The High Temperature Resisting Drilling Fluid System Of The Big Hole Horizontal Well Located In The Du 84 Block

The SAGD "121 project" of Du 84 block is a key project of thermal recovery of heavy oil reservoir with horizontal well SAGD technology for the purpose of developing reservoir of edge,improving oil reserves producing level,the depth of the reservoir is 650-700 m.Total 3 horizontal Wells in large size were deployed to cultivated single well yield of 200 t/d,which drilled firstly with 311.1 mm bit,secondly with 444.5 mm bit for reaming,finally with 308 mm bit drilling the horizontal section,about 600-700 m long.The well of the type has now been known to the most difficult,because of high temperature chamber and no available construction experience at home and abroad.In the paper,according to the technical problems of drilling fluids such as high temperature resistance of drilling fluid,wellbore creep,narrow density window,oil sands,wellbore cleaning and lubrication anti-jamming etc.,the reservoir characteristics of 260 ℃ high temperature chamber and the existing mature drilling fluid system,the positive-gel drilling fluid system and the polysulfide drilling fluid system of anti-high temperature were selected as the first choice system of the different well sections.And through a large number of indoor experiments,the treatment agent with high capability of resisting high temperature,stable performance and good sealing ability was selected.Formulation studies and validation were done indoors,and finally optimize the drilling fluid formula continuously to achieve the best results in site construction.Through the site construction of three wells,the special technology of SAGD shallow large size horizontal well drilling fluid obtains the good application effect: drilling fluid performance can meet the demand of long time wait after stop drifting and resist temperature of 220 ℃;"mechanical support balance" of borehole wall stability technology can guarantee the borehole unobstructed;this emulsification effect is good;torque and friction decreases in directional drilling process.Many technical problems can be largely solved existing in the construction,the resistance to temperature system is fully demonstrated to be suitable for SAGD horizontal well site construction,and field application effect is good.