PROCEDURE FOR CONSTRUCTION OF HORIZONTAL DRAIN HOLE IN UNSTABLE MOVEABLE ROCK AND DRILLING ASSEMBLY FOR ITS IMPLEMENTATION Russian patent published in 2011 - IPC E21B7/20 E02F5/18 

FIELD: gas and oil production.

SUBSTANCE: procedure for construction of horizontal drain hole in unstable moveable rock and drilling assembly for its implementation are designed for drilling horizontal drain holes of big length in most complicated geological conditions. The procedure consists in inclusion of additional protective strings with diametres decreasing to drilling lengthwise axis and a removable vibratory-percussion device into a complex of the drilling assembly. This facilitates loading the protective string without interruption of its vibration when there is achieved maximal length of the hole with consideration of strength of connection. The protective string is stopped when it achieves its maximal length for the second time. It is sealed and the additional protective string of less diametre is concentrically lowered in it till connection with a rock destroying tool. Further, drilling is carried out with the additional protective string rotating it in the direction opposite to the rotational direction of the preceding protective string. A gap between the stopped preceding protective string and additional moveable protective string is washed through drilling string and additionally independently and continuously washed with water under pressure exceeding that one of formation. The protective string is stopped when its reaches maximal length of the hole upon vibration. A new additional string of still less diametre is lowered for successive drilling and stop operations are repeated a required number of times for obtaining required length of a hole.

EFFECT: multiple increase of horizontal drain hole length, increased drilling length of each of alternating protective strings, raised efficiency of drain complexes, increased reliability, prevention of sand ingress between protective strings.

2 cl, 4 dwg, 2 ex