BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
FIG. 1 is a cross-section of a conventional core drill assembly with an non-adjustable TFA defined by the area of the annulus between the core head and the lower shoe, and the area of the drilling fluid ports.
FIG. 2 is a cross-section of a core drill assembly with a seal structure between the core head and the lower shoe and replaceable nozzles;
FIG. 3 is a partial cross-section of a core drill assembly including an O-ring or wiper seal type seal assembly;
FIG. 4 is a partial cross-section of a core drill assembly including a split-ring type seal assembly;
FIG. 5 is a partial cross-section of a core drill assembly including a labyrinth seal assembly; and
FIG. 6 is a partial cross-section of a core drill assembly including a restrictor sleeve.
DETAILED DESCRIPTION
FIG. 2 schematically depicts a core drill assembly 10 of the present invention including replaceable nozzles 36 at the discharge ends of fluid courses 20, and at least one seal assembly 40 disposed between the core head 14 and the lower shoe 18. These features allow the operator to change the TFA of the core drill assembly 10 and optimize the HSI. The operator can select replaceable nozzles 36 having a discharge opening 34 of an appropriate diameter to adjust TFA. Thus, if a volume of drilling fluid is pumped under pressure, at a substantially constant flow rate, down the drill string, seal assembly 40 will divert substantially all of the drilling fluid volume away from the annulus 50 and into the fluid courses 20 where the drilling fluid will exit through discharge opening 34 of replaceable nozzles 36. The diameters of discharge openings 34 will affect both the rate of discharge and the velocity of the escaping drilling fluid. Under optimized conditions, as provided by the present invention, the drilling fluid, emanating from the discharge openings 34, will effectively clear cuttings away from the face 16 and of core head 14 and properly cool cutters 60. The optimum diameter of discharge openings 34 for a specific material or formation, and core head or core size, can be determined or predicted by the use of historical data, including ROP measurements. As shown at the left-hand side of FIG. 2, the seal assembly 40 may be partially received in a groove in ID of the core head 14 or, as shown at the right-hand side of FIG. 2, the seal assembly 40 may be partially received in a groove in the exterior of the lower shoe 18. As core head 14 rotates about lower shoe 18 during a coring operation, fluid flow therebetween will be substantially restricted by seal assembly 40, as indicated by the smaller size of the arrows below annulus 50 in comparison to those in fluid courses 20.
FIGS. 3 and 4, are partial cross-section views of core drill assembly 10 provided, to show additional detail of several embodiments of the at least one seal assembly 40. The at least one seal assembly 40 is positioned in the annulus 50, or the gap defined between the ID of core head 14 and the outside of the lower shoe 18. The seals 42 and 44 are installed in grooves 46 formed in the ID of core head 14. The seals 44 shown in FIG. 3 may comprise an O-ring or other continuous ring type that may have a round or oval cross-section, or may include lips which function as “wipers,” as shown. The material of seals 44 may include, but is not limited to, rubber, neoprene, or polyethylene or a combination thereof. The seals 42 shown in FIG. 4 are of a split-ring design which rides loosely in the grooves 46. Examples of suitable materials for the split-ring seals 42 are nylon and Teflon® polymers. The at least one seal assembly 40 will substantially restrict the flow of the drilling fluid pumped down the drill string, forcing the drilling fluid to bypass the annulus 50 and into the fluid courses 20, traveling in the direction of flow arrows 26.
FIG. 5 is a partial cross-section view of a core drill assembly 10 including a labyrinth seal 48 having a plurality of radially projecting, axially spaced annular elements separated by labyrinth slots 56. The labyrinth seal 48 is formed into the structure of one of the core head 14 ID or the exterior surface of the lower shoe 18. However, a labyrinth seal 48 with mating, interdigitated elements or components as shown in broken lines at E can be formed with the cooperating parts disposed on both the core head 14 ID and the lower shoe 18. The total number of labyrinth slots 56 is not specified, and will vary depending on the expected pressure differential between the pumped drilling fluid and drill work face. The labyrinth seal 48 must have sufficient length and number of labyrinth slots 56 to effectively seal annulus 50. With annulus 50 sealed, the drilling fluid will enter fluid courses 20, flowing in the direction indicated by flow arrows 26.
It is also contemplated that the seals may be carried on the exterior of the lower shoe 18 instead of on core head 14, or may be carried on both components. It is also contemplated that a seal comprising an upwardly facing packer cup with a frustoconical elastomeric skirt may be utilized in addition to, or in lieu of, other seal configurations. Chevron-type seals, as well as metallic or elastomeric seal back-up components, may also be employed.
FIG. 6 depicts yet another embodiment of the present invention, wherein a seal element in the form of restrictor sleeve 64 is disposed on an annular shoulder 62 machined or otherwise formed on the ID of the core head 14, and retained therein through the use of an appropriate bonding agent, such as BAKERLOK® compound, available from various operating units of Baker Hughes Incorporated, assignee of the present invention. As with the previous embodiments, discharge openings 34 of replaceable nozzles 36 may be selected for optimum TFA. A conventional lower shoe 18 is run inside of core head 14, and extends longitudinally therethrough. The outer surface (shown in broken lines for clarity) of lower shoe 18 is in close proximity to the ID of restrictor sleeve 64, so that a very small clearance radial clearance C, for example about 1 mm, is achieved This small, annular clearance C between lower shoe 18 and restrictor sleeve 64, while permitting rotation of lower shoe 18 and restrictor sleeve 64 about lower shoe 18, will substantially restrict the flow of the drilling fluid pumped down the drill string, forcing the drilling fluid to bypass the annulus 50 and into the fluid courses 20 to exit through discharge openings 34 of replaceable nozzles 36.
While the present invention has been depicted and described with reference to certain embodiments, the invention is not so limited. Additions and modifications to, and deletions from, the described embodiments will be readily apparent to those of ordinary skill in the art. The present invention is, thus, limited only by the claims which follow, and equivalents thereof.
Patent Application
20070261886
