Abstract: For single perforation in long-hole sections of horizontal wells with slim holes,it is apt to form the gas pressure plug at the moment of perforation,damage the casing and cement mantle,or cause a lot of sand production from the formation which may plug the well bore and then result in sticking the gun and burying the well.Based on thorough study and field test,the ?60 mm mechanical hydraulic chronotron is developed,and a set of perforation techniques are developed for the horizontal wells with middle or long radius.The chronotron,which has been designed by using the hydraulic delay principle,can control the break time of all groups of detonators,different sizes of delay pins can reach different delay time,the perforating gun is detonated by step,time and interval,and the perforating energy is dispersed.So the above mentioned problems exist in the TCP perforation of long-hole sections of horizontal wells are solved.The hydraulic chronotron provides the important assurance for the safety of TCP perforation in horizontal wells.It has been applied to the field for many times and has obtained good results.