Abstract: A pair of parallel horizontal wells were accomplished for the steam-assisted gravity drainage in order to exploitation Du 84 extra-viscous crude oil block in Liaohe Oilfield, Well Du 84 horizontal 1-1 is a production well (lower); Well Du 84 horizontal 1-2 is a steam injection well (upper). The production well was drilled first, then the injection well. The final true depth, the vertical depth of the target point, the length of horizontal segments were 1214.00m, 796.81m, 325.53m for the first well and 1 189.00m, 760.51m, 307.71m for the second one. The maximum and the minimum vertical interval between the horizontal section of the two wells were 11.98m and 10.43m. The intermediate casing was run into 10~15m of the reservoir, and φ168mm TBS screen pipe and φ177.8mm dead pipe were used for completion and were hanged at the depth of 30m below the intermediate casing shoe with the hook-wall packer. It were described for the geological condition, the design principle of casing program, the design requirement of well profile and the control technique of the hole trajectory in inclined section and horizontal section and so on.