Abstract: Five horizontal wells in TZ-4 reservoir were drilled and completed during the period of April 1994 to February 1996. These horizontal wells are characterized by their average inclination start point of 3, 323.32 m, average true depth of 4, 230.62 m, average vertical depth of 3, 593.50 m, average horizontal segment of 492.01 m, average horizontal displacement of 785.63 m, average drilling period of 195.46 d, initial production over 1, 000 t/d, sturdy production over 6, 000 t/d and investment recovery period of 50d. An optimization design of hole profile and well trajectory was described in this paper. A series of techniques such as technique of deviation prevention and verticality keeping of the vertical bore hole segment, technique of control wellbore trajectory in the inclined portion with power tool or rotary table, technique of control of trajectory in the horizontal section with rotary table combined with DTL guide tool and PDC bit, technique of wellbore trajectory prediction with computer, technique of drilling fluid and technique of well completion were recommended with emphasis in the paper.