Boring or penetrating the earth – With below-ground tool drive prime mover
Patent
1995-06-15
1996-06-18
Dang, Hoang C.
Boring or penetrating the earth
With below-ground tool drive prime mover
175213, 175215, 175324, E21B 2100
Patent
active
055268870
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for drilling holes in the crust of the earth, especially for drilling oil wells.
When drilling for oil, the bit is urged against the bottom of the bore hole by means of drill collars disposed on the drill string above the bit. Drilling fluid is pumped down through the tubular drill string and out through rinsing nozzles of the bit, whereafter the drilling fluid returns into the annulus at the outside of the drill string. The drilling fluid serves two purposes. Firstly, the hydrostatic pressure from the drilling fluid is to prevent reservoir fluid from forcing its way into the hole. The density of the drilling fluid is continuously adjusted in order to maintain hydrostatic pressure balance. Secondly, the drilling fluid is to convey cuttings from the bottom of the hole, upwardly to the surface.
A disadvantage of drill collars in order to give the bit the necessary contact force against the bottom of the hole, is that such drill collars give little effect with drilling in horizontal or approximately horizontal direction. It is known to replace collars with a packer or a piston sealing outwardly against the hole wall, and which is mounted on the drill string just above the bit. The hydrostatic pressure from the drilling fluid within the hole exerts a pressure against the top face of said piston and urges the bit against the bottom of the hole, drilling fluid being pumped from the bottom side of said piston back to the surface by means of a pump of its own or by means of a gas lift. A disadvantage of this known arrangement is that the obtainable contact force acting on the bit is entirely dependent on the density of the drilling fluid. Also, it is a disadvantage that the drilling fluid, which has to convey cuttings to the surface, is the same fluid that has to secure that reservoir fluid does not force its way into the hole; these properties not always being equally combineable.
Also, it is a disadvantage of known drill devices that the density of the drilling fluid has to be monitored and adjusted continuously, in order to maintain the hydrostatic pressure balance within the hole.
The objects of the invention are to provide a device for drilling wherein the bit is urged hydraulically against the bottom of the hole, and wherein drilling fluid returns to the surface without the use of an extra downhole pump or gas lift, and wherein the pressure balance within the hole can be maintained without altering the density of the drilling fluid.
In accordance with the invention, the objects are achieved through the features defined in the following claims.
An embodiment of the invention is described in the following, reference being made to the attached drawings, wherein:
FIG. 1 shows, diagrammatically and partly in section, an oil well with drilling equipment;
FIG. 2 shows, diagrammatically and partly in section, an oil well with drilling equiment applying a sealing layer to the hole wall;
FIG. 3 shows, diagrammatically and partly in section, an oil well with simplified drilling equipment.
In FIG. 1, reference numeral 1 denotes a hole drilled in the crust of the earth. A bit 2 is adapted to be operated from a downhole motor 3 mounted in a drill string 4. Drilling fluid is pumped downwardly through the drill string 4 by means of a pump device (not shown) of known type. Advantageously, the drill string 4 may be of coil pipe type. A piston 5 is disposed on the drill string 4 above the bit 2 and is adapted to slide sealingly against the wall of the hole 1. Advantageously, the piston 5 may be adapted to expand, in order to form the sliding seal against the wall of the hole 1, when the liquid pressure within the drill string exceeds a predetermined value. A return line 6 for drilling fluid is passed through the piston 5 from a volume defined by the bottom and wall of the hole 1 as well as the piston 5. During drilling, the return line 6, which advantageously may be a coil pipe, conducts drilling fluid from the volume 7 to the surface. A seal 8 is disposed within the hole 1, spaced above the p
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patent: 3638742 (1972-02-01), Wallace
patent: 4534426 (1985-08-01), Hooper
patent: 4630691 (1986-12-01), Hooper
Dang Hoang C.
Hochberg D. Peter
Jaffe Michael
Kusner Mark
Rogalandsforskning
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