Drilling method for steam assisted gravity draining oil well

The invention discloses a well-drilling method for steam-aided gravity draining oil well used for drilling an upper well and a lower well which are horizontally parallel; the horizontal well at the upper part is a gas-injection well, and the horizontal well at the lower part is a producing well; the method is characterized in that: one of the two horizontal wells is drilled, and the other is drilled according to drill hole trajectory of the finished horizontal well. Joint measurement control is carried out by utilizing a magnetic-conducting measurement system and a measurement while drilling system, and then the horizontal well section of the second horizontal well, which is parallel to the horizontal well section of the finished horizontal well, is drilled by the guidance of real-time data of the drilling trajectory of the finished horizontal well section, thus forming a magnetic-conducting loop-closed measurement drilling mode which is correspondingly sealed between the finished well and the well to be dril