Wells – Processes – Assembling well part
Patent
1998-02-03
1999-10-12
Bagnell, David
Wells
Processes
Assembling well part
1662428, 285256, 285382, E21B 1916
Patent
active
059642971
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of performing drilling in earth layers with. simultaneous forcing in of casing tubes of plastic or similar material, and a casing shoe for bringing the casing tube with it.
When performing drilling in earth layers one uses a pilot drill bit with a reamer drill bit arranged such that it can be thrown out eccentrically relative to the pilot drill bit and enlarge the hole drilled thereby. Through this the drilled hole can get sufficient dimension to give place, in addition to the drill bit with retracted reamer, for a casing tube entered into the borehole at the same time as the hole is drilled, The casing tube is thereby driven down by a casing shoe welded to the end of the casing tube and acted on by a down-the-hole hammer. The casing tubes normally consist of three meter long steel tubes which are welded to each other when drilling and the tube has been driven down to a suitable level.
SUMMARY OF THE INVENTION
One problem with the handling of the casing tubes is their weight. Another is the possibility of corrosion which in certain cases results in exchange of them to e.g. plastic tubes after finished drilling, a complicated and time-consuming procedure.
One object with the present invention is to eliminate the exchange of casing tubes and a further object is to simplify the handling of casing tubes during the drilling. These and other objects are fullfilled through the use of casing tubes of plastic material already from the beginning, which according to the invention is made possible through a special shape of the casing shoe which gives a strong anchoring in the plastic material. Additional advantageous details appear in the claims and the detailed description.
Through the Swedish patent application 9200563-6 and the corresponding international application WO 93/17215 a casing shoe specially formed for strong anchoring in casing tubes of plastic material is known. This requires joining of plastic material through holes in the casing shoe, which can be difficult to perform with good result at the site for the drilling, why it is best suited for being prefabricated and transported joined to one length of tube to the drilling site. With a casing shoe according to the present invention no joining of plastic material through holes m the casing shoe is needed The joining of the casing shoe with the casing tube can be performed at the drilling site partly with aid of the drill hammer.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described more in detail with reference to; the accompanying drawings in which
FIG. 1 shows, partly in section, the shape of a casing shoe according to the invention, and
FIG. 2 shows an alternative shape of the casing shoe.
DESCRIPTION OF THE BEST MODES FOR CARRYING OUT THE INVENTION
FIG. 1 shows a casing shoe according to the invention, partly in section. This is intended to be used for lining with casing tubes of plastic material or other material which cannot be welded to a conventional casing shoe It can be used with down-the-hole hammers of e.g. the type described in Swedish lay-open print 411139 but can also be used with equipment provided with other types of drill hammers. The casing shoe comprises two separate annular parts with conical sections, between which the casing tube is clamped. The outer ring 3 of the casing shoe is thus formed with a lower strong part 4 connected with an upper part 5 with a conical inner surface 6 which has a diameter which is larger than that of the lower part 4 and slowly increases until the diameter of the outer surface 7 is reached. The outer surface 7 of the outer ring 3 of the casing shoe has a substantially constant diameter along the entire length of the outer ring and it is substantially the same as the outer diameter of the casing tube 10. The inner ring 8 of the casing tube has in a corresponding way an inner surface 9 with substantially constant diameter adapted to the outer diameter of the drill hammer 16. The inner ring 8 has a substantially
REFERENCES:
patent: 1949668 (1934-03-01), Watherhead, Jr.
patent: 2470508 (1949-05-01), Maky
patent: 5813484 (1998-09-01), Ekstrom
Bagnell David
Kang Chi H.
Stone Mark P.
Svenska Borr AB
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