US 3250578 A
Description (OCR text may contain errors)
y 1966 J- w LUBBES 3,250,578
WELL APPARATUS Filed Jan. 27, 1964 Mack W. 045,619;
ATTORNEY Filed Jan. 27, 1964, Ser. No. 340,363 3 Claims. (Cl. 3084) This invention pertains to drill collars and more particularly to stabilizer drill collars, useful in the rotary system of earth drilling, e.g. in drilling oil and gas wells.
Heretofore it has been customary to employ conventional stabilizers in between drill collars to maintain the drill collars concentric with the hole already drilled, thereby to continue drilling in a straight line. Because the stabilizers are relatively short in length, e.-g. one or two feet, compared to the twenty to thirty foot length of the usual drill collar, there is still considerable opportunity for side play and eccentric positioning of the drill collars, and also for bending and whip of the drill collars in between the stabilizers.
The difliculty with conventional stabilizers is aggrevated if the formation being drilled is unconsolidated or shifting, resulting in cave-ins. The resultant enlargements in the hole being drilled must be traversed by the stabilizers as drilling proceeds and when a stabilizer is'in an enlarged portion of the holeit becomes ineffective.
According to the present invention the aforementioned difliculties are overcome by providing the drill collar with stabilizing means distributed along substantially the entire length of the drill collar.
Conventional stabilizers comprise tubular bodies with connecting means at each end whereby the stabilizer body can be connected in the drill string to transmit mechanical forces and convey fluid between the adjacent portions of the drill string. The outer periphery of the body is provided with radially extending means, such as ribs, to
United States Patent contact the wall of the holes being drilled, thereby to I prevent lateral movement of the tubular body and kee it concentric with the hole. The spaces between the ribs provide fluid passages in which annulus fluidcan pass by the stabilizer. The longitudinal extent of such ribs varies from two to four times the diameter of the well bore, or otherwise expressed, the length of the ribs is of the same order of magnitude as the circumference of the well bore.
-In contrast thereto, the wall contacting means of the present invention is a whole order of magnitude longer, extending some ten times the circumference of the hole being bored. This in itself presents problems. As is stated in US. Patent 2,829,864 on a Method and Apparatus for Straightening Well Bore Holes: Use of oversized drill collars and reamers often causes crowding of jamming of the drill string. (Col. 1, lines 33-34.) The crowding results in poor fluid flow in the annulus and the loss of fluid flow is a cause of jamming.
According to the present invention, adequate annulus flow is assured by the combined action of three structures:
('1) Only four wall contacting ribs, each having'only about 30 degrees circumferential extent, leaving an adequate passage about 60 degrees, between each adjacent pair of ribs, for fluid flow.
(2) The sides and bottoms of each fluid passage between the ribs are one continuous concave surface, e.g., comprising a segment of a cylinder, eliminating any sharp corners wherein mud might be caught and build up a flow restricting plug.
(3) At intervals along the length of the drill collar all the ribs are interrupted leaving an annular fluid passage extending all around the drill collar interconnecting the longitudinal passages between the ribs, whereby if there is any blockage in one of the longitudinal channels, the effect thereof is minimized, in that the blockage does not cut off fluid flow for the whole length of the drill collar.
A further feature of the invention is the circumferential displacement or offsetting of the ribs at each of the interruptions forming the annular fluid passages. Thus, despite the fact that only four ribs, each of but 30 degrees circumferential extent, are employed, there is provided wall contacting means over a major portion of the circumference of the drill collar. Nevertheless, due to the interruptions and offsetting of the ribs, there is less likelihood of the drill collar becoming jammed in the hole.
The ribs may be provided with hard facing, i.e. tungsten carbide, to prevent wear on the ribs as drilling proceeds, the diameter at the rib peripheries being almost full gage, e.g., 8%" for an 8%" hole. Using adrill collar of this near approach to full gage constitutes what is called packed hole drilling.
To distinguish the subject drill collar from ordinary drill collars, the present drill collar may be referred to as a packed hole drill collar or a stabilizer drill collar. In an ordinary drill collar the outer diameter is the same as that of the threaded box provided at one end thereof for connection to other parts of the drill string, whereas the stabilizer drill collar of the present invention has a diameter at the outer periphery of the ribs that is considerably larger than the box at one end of the collar, in fact the groove bottoms have about the same radial extent from the collar axis as the outer periphery of the box.
For a detailed description of a preferred embodiment of the invention reference will now be made to the accompanying drawing wherein:
FIGURE 1 is an elevation of a stabilizer drill collar embodying the invention, same being shown connected to a drill bit;
FIGURE 2 .is a horizontal section taken at plane 22 of FIGURE 1; and
FIGURE 3 is a horizontal section taken at plane 3-3 of FIGURE 1.
Referring now especially to FIGURE 1 there is shown a stabilizer drill collar including a tubular body 10 hav ing a fluid passageway 11 therethrough (see also FIG URES 2 and 3). At the upper end of the body there is provided means for connecting the drill collar to another part of a drill string, said means being in the form of a threaded box 12. Means for connecting the drill collar to another part of the drill string is also provided at the lower end'of the drill collar, this means being in the form of a threaded pin 13. As shown, pin 13 is connected to a double box sub 14, which in turn is connected to a drill bit 15. If desired, the lower end of the drill collar could be provided with a box, similar to box 12 formed at the upper end thereof, thereby eliminating the need for sub 14.
Between the upper and lower ends of the drill collar it is provided with a plurality of longitudinally spaced groups of longitudinally extending, circumferentially spaced ribs, there being four ribs in each group. Regardless of which group a rib is in, it is designated by reference number 20. As shown in FIGURE 1, the radial extent of the rib 20 is substantially the same as that of the bit 15, in practice the ribs might have the same or slightly less, e.g., /2", /16", or /s less, radial extent that the bit according to the preference of the user, as dictated by operating conditions. In any case the radial extent of the ribs will be considerably greater than that of box 12 and the land 21 adjacent pin 13.
Between each adjacent pair of ribs there is formed a longitudinal fluid passage 22. As best shown in FIG- UR'ES 2 and 3, these passages are concave channels, whose surfaces are segments of cylinders. T he bottoms land 21 and the adjacent group of ribs 22. At the upper end of the drill collar there is an annular necked down portion 27 with a shoulder 28 therebove providing space and means for engagement of the upper end of the drill collar by elevators. It is to be noted that not only is the continuity of the longitudinal extent of the ribs 22 interrupted by the annular channels 25,- whereby the ribs are disposed in longitudinally spaced apart groups, but in addition the ribs in each group are staggered relative to those in each adjacent group, the j ribs in one group being aligned with the longitudinal fluid channels in the adjacent groups.
Areas at the outer periphery of ribs may be provided with hard facing as shown at 30. Any suitable form of hard facing such as tungsten carbide, may be used. The ribs are of about thirty degrees circumferen tial extent'compared with about sixty degrees circumferential extent of the longitudinal channels, there being four ribs and four channels per group.
While a preferred embodiment of the invention has been shown and described, modifications thereof can be made by one skilled in the art without departing from the invention.
That being claimed is:
1. A stabilizer drill collar comprising a tubular body having threaded connection means at each endfor connection to a drill string, a plurality of longitudinally spaced groups of circumferentially spaced longitudinally extending ribs disposed along the length of the body,
being aligned with the longitudinal passages between the ribs in the adjacent groups of ribs, said groups of ribs and annular fluid passages extending substantially the full length of said drill collar from adjacent the threaded connection means atone end of the drill collar to adjacent the threaded connection means at the other end of the drill collar, their being four ribs in each group, the circumferential extent of each longitudinal fluid pass-age being of the order of twice the circumferential extent of each r-ib.
2. The combination according to claim 1 wherein said annular and longitudinal fluid passages are concave, the bottom of said passages being of less radial extent than that of the-outer periphery of said threaded connection means.
3. The combination according to claim 1 wherein said ribs are of substantially full gage with respect to the hole to be bored, compared to the lesser diameter of the threaded connection means, and are provided with bar facing at their outer peripheries.
References Cited by the Examiner UNITED STATES PATENTS 349,192 9/ 1886 Woodhouse 17523 1,031,643 7/ 1912 Hahn 246-210 1,374,946 4/ 1921 Nebergal-l 308-4 2,188,119 1/ 1940 Prentice 166233 2,466,239 4/ 1949 Holcombe 166-176 DAVID J. WILLIAMOWSKY, Primary Examiner.
L. L. IOH-NSON, Assistant Examiner.