Methods and systems for drilling

摘要

A method of controlling a direction of drilling of the drill string (110) used to form an opening in a subsurface formation (102), comprises varying a speed of the drill string during rotational drilling such that the drill string (110) is at a first speed during a first portion of the rotational cycle and at a second speed during a second portion of the rotational cycle wherein the first speed is higher than the second speed, and wherein operating at the second speed in the second portion of the rotational cycle causes the drill string to change the direction of drilling.