Process and apparatus for automatic drilling

Claim 1

A process for automatically optimizing the penetration rate of a drill bit suspended from drill pipe, said drill bit being driven in rotation by a motor whose torque decreases with an increasing of its rotation speed, and said drill bit having a penetration rate which, as a function of the weight exerted on the drill bit, reaches a maximum value for an optimum value of the weight, said process comprising measuring the tension on the drill pipe, periodically determining the penetration rate of the drill bit, automatically adjuSting the linear speed of the drill pipe at the ground surface so as to provide values of the linear speed which are successively greater and lower than the rate of penetration of said drill bit into the ground, the variation in linear speed causing alternatively a decrease and an increase in the tension on the drill pipe, thereby producing an oscillation in the value of the weight on the drill bit about the optimum value of said weight, wherein during each period when the linear speed at the surface is greater than the penetration rate, said penetration rate is periodically determined and the highest value thereof is recorded, effecting a transition from said period when said linear speed is greater than the penetration rate to a second period during which the linear speed at the surface is lower than the penetration rate when said penetration rate has reached a preselected value, and effecting a transition to another period wherein the linear speed at the surface has a greater value than the penetration rate when the tension on the drill pipe reaches a preselected limit-value, said tension increasing to said preselected limitvalue.

Claim 9

An apparatus for automatically optimizing the penetration rate of a drill bit located at the lower end of a drill pipe, said drill bit being driven in rotation by a motor whose torque decreases with increasing rotation speed and having a penetration rate which, as a function of the load applied thereon, reaches a maximum value for an optimum value of this load, this apparatus comprising means for measuring the tension exerted on the drill pipe, means for evaluating the successive values of the penetration rate and control means for sequentially performing a progressive increase and a progressive decrease of the load on the drill bit, analyzing means connected to said means for evaluating the penetration rate and adapted to determine and record during each period of increasing load the highest value detected by said evaluating means, first actuating means operatively connected to said control means, to said evaluating means and to said analyzing means, said first actuating means elaborating a first limit-value as a function of said highest value recorded by said analyzing means and initiating a decrease in the load exerted on the weight, when the penetration rate reaches, while decreasing, said first limit value and second actuating means operatively connected to said control means, said second actuating means elaborating a second limit-value and initiating an increase in the load exerted on the drill bit when the tension on the drill pipe has reached, while increasing, said second limit value.

Claim 10

An apparatus for automatically optimizing the penetration rate of a drill bit located at the lower end of a drill pipe, said drill bit being driven in rotation by a motor whose torque decreases with increasing rotation speed and having a penetration rate which, as a function of the load applied thereon, reaches a maximum value for an optimum value of this load, this apparatus comprising means for measuring the tension exerted on the drill pipe, means for evaluating the successive values of the penetration rate and control means for sequentially performing a progressive increase and a progressive decrease of the load on the drill bit, analyzing means connected to said means for evaluating the penetration rate and adapted to determine and record during each period of increasing load the highest value detected by said evaluating means, first actuating means operatively connected to said control means, to said evaluating means and to said analyzing means, said first actuating means elaborating a first limit-value as a function of said highest value recorded by said analyzing means and initiating a decrease in the load exerted on the weight, when the penetration rate reaches, while decreasing, said first limit value and second actuating means operatively connected to said control means, said second actuating means elaborating a second limit-value and initiating an increase in the load exerted on the drill bit when the tension on the drill pipe has reached, while increasing, said second limit value.