Boring or penetrating the earth – Processes – Sampling of earth formations
Patent
1994-05-16
1995-10-24
Dang, Hoang C.
Boring or penetrating the earth
Processes
Sampling of earth formations
175393, 1754051, E21B 1002, E21B 1060
Patent
active
054602300
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a core bit, in particular for a reservoir evaluation coring, comprising: the cutting edges being circumscribed together within an imaginary envelope disposed around a core to be taken, the body.
Core bits of the hereabove defined type are already known. The nozzles therein are formed by bored rectilinear outlets.
An important problem, particularly in the case of the above mentioned evaluation coring, consists in reducing as much as possible the washing of the core during the coring operation, as well at the cutting place as within the bit. The washing can cause for example coring liquid to penetrate into the core to the detriment of various fluids which are contained therein before the coring operation, which may contaminate the core in such a manner that the evaluation of a subsoil as to its capacities for serving as a reservoir or as to its content of searched products becomes impossible. However, the bottom of the groove cut by the bit around the core, has always to be provided with coring liquid, in order to cool the elements which are heated due to friction and in order to evacuate the fragments released during the coring so as to assure an efficient cleaning of the bit and the bottom of the groove.
An object of the invention is to solve this problem by acting upon factors which influence the contact between the coring liquid and the core while assuring a sufficient flow rate of said liquid in order that it fulfils its essential functions which are known by the man skilled in the art.
A factor influencing said contact of coring liquid concerns the orientation of this liquid with respect to the core in formation.
To this end, at least one nozzle has, according to the invention, an outlet deflecting the liquid jet substantially obliquely forwards with respect to the rotation axis of the body, away from the core, preferably according to an angle larger than 45.degree., and advantageously larger than 50.degree..
Advantageously, the invention provides that the deflected nozzle emerges between two blades in a manner such as to create a detachment effect of a stream of coring liquid situated near the core and/or the bit.
In this way, the coring liquid is removed very quickly from the core and, as it cannot stagnate close to the latter, does not contaminate the core. Moreover, due to the detachment effect, the liquid pressure is locally low, in particular near the core, and this liquid is not pressed into the core but may possibly simply cover it with a protective layer which can prevent liquids contained in the core from escaping and that consequently wrong evaluations would be made. The liquid pressure is advantageously adjusted to avoid an extraction of liquids contained in the core.
In a very advantageous embodiment of the invention, the nozzle comprises at least one inserted piece for realizing the deflection, the inserted piece being preferably made of a material having a higher abrasion resistance than the material of the bit, and is advantageously made of sintered carbide.
From the point of view of the users costs, it is advantageous to make the place acted upon by the deflecting coring liquid separately from the body in such a manner that this place can be replaced in the case of wear without having to replace the entire bit or to recondition it thoroughly. It is still more advantageous to make this place in a manner such as to prolong its life. Moreover, the use of an inserted piece allows to remove it in order to make for example a cleaning of the corresponding nozzle easier.
In a preferred embodiment of the invention, an inner hollow core retaining element, which is supported by a string of rods to which the bit is attached, is associated with the bit, in such a manner that a passage gap for letting coring fluid through is formed with respect to this bit substantially around the core, preferably near the cutters, the flow rate of liquid through the passage gap being smaller than 25% of the total flow rate of liquid flowing out through this passage gap and through s
REFERENCES:
patent: 1663025 (1928-03-01), Phipps
patent: 2264617 (1941-12-01), Carpenter et al.
patent: 3095935 (1963-07-01), Hildebrandt et al.
patent: 3215215 (1965-11-01), Kellner
patent: 3322218 (1967-05-01), Hilderbrant
patent: 3565192 (1971-02-01), McLarty
Baroid Technology Inc.
Dang Hoang C.
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