US1834320A - Core drill - Google Patents

Description

(5. O. SUMAN CORE DRILL Filed March 13, 1928 m ma 0 f, w 6 q ATTOENE) A/ ll l atentcd ec. EQEBE enonen 0. so, or car. cnnran, cauronnm, ASSIGNOR T Assocmriao on. comrm, or SAN rorsco, CALIFORNIA, A CORPORATION; or cmroaam cone L Application aia Mai-011 13, 1928. Serial No. 261,323.

This invention relates to core drills adapted to be used to determine geological formations, and contemplates the provision of a tool, having a novel form of core barrel.

The object of this invention is to construct a tool of the character referred to, which is designed primarily to produce better and longer cores under all conditions.

The present practice is to bring the core 1 barrels to the surface, unscrew the three foot sections, and extract the core from each section. Thecores are often tightly wedged in the barrels and it is necessary to force the core up with a screw auger, and in some cases it is even necessary to split the barrel with an acetylene torch. In view of such conditions,

it is easily seen that there is a great amount I offriction between the core and the barrel, and the longer the core the greater the friction. This frictional resistance prevents the taking of longer cores and also explains the failure in some instances to core sand, because .the path around the outside of the core bit ofiers less resistance than the core barrel.

It is therefore a further object of this invention to reduce this frictional resistance between the core and the barrel.

Briefly, this may be accomplished by increasing in an upwardly direction the cross 0 section of the inner core barrel, so that an increase in the length of the core will tend to reduce the frictional resistance in the core barrel. This friction may also be reducedby perforating the core barrel, so that some of the mud coating on the core may escape through the holes and be carried out by the circulating liquid.

Other objects and advantages of this invention will be apparent from the following 40 description, taken in conjunction with the accompanying drawing, in which:

The figure represents a vertical section of a core drill, embodying the features of this invention. v. In the drawing, the numeral 1 represents a drill pipe which is of constant cross section and to which is attached a core bit 2, which may be of any type now used by those skilled in the art. Within the drill pipe 1 there is an 60 outer core barrel 3, also of constant diameter,

which is provided at its bottom with passages 4 and5, which communicate with the interior of the barrel., i Within this outer core barrel 3 there is an inner core barrel 6 having perforations 7 therein and whose cross section decreases gradually from the top down to the core bit 2. In addition, the core barrel 6 is provided with an openin 13 at the top to allow the mud-laden flui in the core barrel to escape as the core is being taken and thereby preveint an increase of pressure within the barre In operation, mud-laden fluid is circulated down the interior of the drill pipe under pressure and passes between the drill pipe and the outer core barrel 3 in the direction of the arrows. "At the bottom, part of this fluid passes out of the drill pipe through thepassages 8 and 9 and upwardly in the direction of the arrows, while the other part passes through the passages 4i and 5 and is circulated upwardly in the direction of the arrows between the core barrels. The valve 10, which is diagrammatically illustrated, allows the mud-laden fluid which has been circulated between the core barrels, to pass through the pipe '11 and finally become discharged through the outlet 12 in the drill pipe 1.

It should be remembered in the construction of this inner core barrel-that the bottom section of the barrel should have a very slight tape-r, and in fact, in some instances it maybe advisable to allow the diameter to remain unchanged, for the reason that if the friction is reduced "beyond a certain point the core may be lost when the drill pipe is withdrawn. i

This particular type of core drill presents many advantages over the types now in use.

Naturally, the gradual increase upwardly in the cross section of the inner core barrel reduces the undesirable resistance as the core becomes longer, which" is just the opposite of the condition encountered at the present time. The circulation of mud-laden fluid upward between the inner and the outer core barrels definitely and positively does away with any downward thrust on or in the core barrel. The perforations on the inner core 10 barrel release the frictional strain set up in the core barrel by mud-laden fluid, and in addition the friction is reduced by the slight upward force of the movin laden fluid on the outside 0 the inner barrel.

With the improvements herein mentioned embodied in a core drill, it is now possible to obtain longer and better cores, to the extent that the length of the cores taken will be at least double those which are now taken by the present core drills.

This reduction of the pressure of the mud coat against the actual formation core, due to the release of pressure by perforations permitting the escape of mud-laden fluid and also the increase in diameter of the core bar-, rel as the core rises in the barrel naturally brings up the question as to what happens to the formation core when this occurs. In the case of shale, nothing happens, as the shale is sufiiciently hard and compact to resist any minor forces of the formation core above coming into the barrel from below to compress it. In the case of loose sand or soft clay, there may be a slight tendency to compress or spread out, but this is overcome somewhat by the mud coating and also by the upward lifting pressure exerted by the movement of the mud-laden column of fluid, which is continually in efiect outside the inner barrel.

Having now more particularly described my invention, what I claim is:

1.111 a core drill, a drill pipe, a second column of mudneeeaso drill pipe, a second pipe within the drill pipe and spaced therefrom, a perforated core barrel within the second pipe and spaced therefrom, and means for positively circulating liquid upwardly from the interior of the drill pipe between said second pipe and core barrel to the exterior of the drill pipe.

6. In a core drill the combination of; a drill pipe, a second pipe within the drill pipe and spaced therefrom, a valved discharge passage from the top of said second pipe to the exterior of the drill pipe, a core barrel within the second pipe and spaced therefrom, and means for passing liquid upwardly from the interior of the drill pipe between said second pipe and core barrel. v

7. in a core drill .the combination of: a drill pipe, a second pipe within the drill pipe and spaced therefrom, a tapered perforated core barrel with the second pipe and spaced therefrom, a valved discharge passage from the top of said second pipe to the exterior of the drill pipe, and means for passing liquid from the drill pipe between said second pipe and core barrel.

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pipe within the drill pipe and spaced therefrom, a perforated core barrel tapering downwardly within said second pipe and spaced therefrom, and means for circulating liquid between the drill pipe and the core barrel.

2. In a core drill, a drill pipe, a second pipe within the drill pipe and spaced therefrom, a perforated core barrel tapering downwardly within said second pipe and spaced therefrom, and passages connecting the interior of the drill pipe to the interior of the second pipe, whereby mud-laden fluids may be circulated upwardly between the core barrel and said second pipe.

3. In a core drill the combination of: a drill pipe, a second pi e within the drill pipe and spaced there rom, a bore barrel within the second pipe and spaced therefrom,

and means for positively circulating liquid upwardly from the interior of the drill pipe between said second pipe and corebarrel.

4. In a core drill the combination of: a drill pipe, a second pipe within the drill pipe and spaced therefrom, a core barrel within the second pipe and spaced therefrom,

and means forpositively circulating liquid upwardly from the interior of the drill pipe between said second pipe and core barrel to the exterior of the drill pipe.

5. In a core drill the combination of: a

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