Abstract This abstract describes a system by means of which the precise position of the drill bit, in three dimensions, in the earth, can be determined during the drilling operation with a minimum of effort and interruption to the drilling process. It provides placing a motion sensor on the drilling apparatus, and a plurality of vibration sensors or geophones, positioned in a twodimension array on the surface of the earth, above the expected position of the drill bit. To make a measurement from which can be determined the position of the bit, the drill stem is raised a selected distance and suddenly released, so that it will fall in the borehole, and the bit will strike the bottom of the hole. This impact will cause an elastic wave to be generated at the bottom of the borehole. The elastic wave will be transmitted through the earth as a spherical wave upward to the surface, and will be detected by the geophones. The sensor at the drilling apparatus determines the instant at which the drill pipe starts to fall, from which time can be calculated, knowing the length of the drill pipe, the time when the bit strikes the bottom of the drill hole. This determines the initiation time of the elastic wave. The arrival times at the geophones of the elastic wave can be measured, and the position at which the elastic wave originated can be determined.
The method of determining the position in the earth of the bottom of a borehole, during the drilling of said borehole by the rotary method, the length of drill pipe being known, comprising: a. placing a plurality of sensors in the earth in a known geometric pattern above the expected position of the bottom of the borehole, said sensors adapted to detect and transduce the vibrations of the earth to corresponding electrical signals, and amplifying said transduced signals; b. lifting the drill pipe a selected distance, and sudDenly releasing the drill pipe, so that it falls in the borehole until the drill bit strikes the bottom of the well bore, whereby the impact of the drill bit on the bottom of the well bore will generate an elastic wave in the earth; c. determining the time of release of said drill pipe; d. recording as a function of time said amplified transduced signals and determining the times of arrival of said elastic wave at said sensors; and e. from the known time of release of said drill pipe and the known length of drill pipe and the times of arrival of said elastic wave at said sensors, determining the position of said bottom of the borehole.
Claim 2
Independent Claim
206 words
The method of determining the position in the earth of the bottom of a borehole, during the drilling of said borehole by the rotary method, the length of drill pipe being known, comprising: a. placing a plurality of sensors in the earth in a known geometric pattern above the expected position of the bottom of the borehole, said sensors adapted to detect and transduce the vibrations of the earth to corresponding electrical signals, and amplifying said transduced signals; b. lifting the drill pipe a selected distance, and sudDenly releasing the drill pipe, so that it falls in the borehole until the drill bit strikes the bottom of the well bore, whereby the impact of the drill bit on the bottom of the well bore will generate an elastic wave in the earth; c. determining the time of release of said drill pipe; d. recording as a function of time said amplified transduced signals and determining the times of arrival of said elastic wave at said sensors; and e. from the known time of release of said drill pipe and the known length of drill pipe and the times of arrival of said elastic wave at said sensors, determining the position of said bottom of the borehole.
Claim 3
Dependent Claim
32 words
The method as in claim 1 including the step of determining from the known time of release and the known length of drill pipe, the time of generation of said elastic wave.
Claim 4
Dependent Claim
39 words
The method as in claim 1 in which said sensors are arrayed within a circle the center of which is at the well head, and the perimeter is outside the maximum expected radius of said bottom of said borehole.