Well ADM6-4H was completed by MWD and screw drilling tool combining construction in AHDEB oilfield, which is a 6-inch slim hole with the length of 1500m in horizontal section and the maximum horizontal displacement of 1915.17m, and is also a horizontal well with the maximum horizontal displacement in AHDEB oilfield at present. Polysulphonate oil-mixing drilling fluid system was used in the fourth spudding horizontal section drilling, for its outstanding application effects of sand carrying, borehole wall stability and lubricating, the drilling speed was fast with small drilling torque and stable drilling fluid properties; there were no borehole instability, lost circulation, sticking and back pressure.