Mud Saver For Drilling Rigs

Abstract

Apparatus is disclosed for attaching to the lower end of the kelly of a drilling rig to keep the drilling mud that is in the kelly from running out, when the kelly is disconnected from a drill string for any reason, e.g., to add another joint of pipe to the string. The mud saver includes a two-piece tubular housing for connection to the lower end of the kelly, between the kelly and the upper end of a string of drill pipe. An elongated sleeve of resilient elastomeric material is located in the housing with its upstream end clamped open between the two sections of the housing so all the mud pumped through the kelly into the drill pipe will pass through the sleeve. The downstream end of the sleeve is held closed by two springs located on opposite sides of the sleeve. These springs exert only enough force on the lower end of the sleeve to hold it closed against the hydrostatic pressure of the drilling mud above the sleeve when the kelly is disconnected from the drill string to thereby keep the mud in the kelly from flowing out its lower end. When the kelly and mud saver are reconnected in the drill string, drilling mud can be pumped down the kelly, through the sleeve, and into the drill string, and the pressure of the mud is more than sufficient to force the lower end of the sleeve open to permit the mud to flow through.

Description

This invention relates to apparatus for reducing the drilling mud losses of rotary drilling rigs and, in particular, to apparatus for reducing the mud losses associated with disconnecting parts of the drill string.

When drilling with the rotary method, drilling mud is circulated into and out of the well bore by pumping the mud down through the drill string. A swivel supports the drill string during drilling operations and provides a rotating fluid connection between the mud pumps and the drill pipe. The swivel usually is connected to the drill pipe through a kelly, which is rotated by a rotary table.

When another joint of pipe is to be added to the drill string or the pipe is to be pulled from the hole, the kelly is disconnected from the pipe string. When this occurs, any mud remaining in the kelly will run out and be wasted. Drilling mud usually contains a mixture of chemicals, some of which are very expensive. In addition, when the mud flows out of the kelly onto the floor of the drilling rig, the floor becomes slick and unsafe for the workmen. Also, the mud is often strongly basic and harmful to workmen's skin and clothing.

The amount of mud lost each time the kelly is unscrewed from or broken out of the string can be reduced by waiting as long as possible after the pumps are shut down and the kelly pulled back up into the derrick. For if the density of the mud in the drill pipe and the mud outside the drill pipe in the annulus is the same, the level of the mud in the pipe will drop to that of the mud in the annulus. This requires time, however, and drilling rig time is very expensive. Further, the density of the mud in the kelly is often less than that of the mud in the annulus for various reasons such as the addition of water to the mud before it is pumped back into the well bore. When this condition exists, the mud level in the drilling string, which includes the kelly and the pipe string, will not fall to the level of the mud in the annulus.

Therefore, it is an object of this invention to provide apparatus to keep the mud in a kelly from running out its lower end when the kelly is disconnected from a pipe string.

It is another object of this invention to provide apparatus that will not interfere with the circulation of mud through a kelly, but which will automatically stop the downward flow of drilling mud in the kelly when the circulation of mud is stopped.

These and other objects, advantages, and features of the invention will be apparent to those skilled in the art from a consideration of this specification including the claims and attached drawings.

The invention will now be described in connection with the attached drawings, in which:

FIG. 1 is a view, partially in elevation and partially in vertical section, of the mud saver apparatus of this invention installed in a pipe string;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a view on an enlarged scale of the portion of FIG. 1 within the circle 3;

FIG. 4 is a view, on an enlarged scale, looking upstream at the valve element assembly of the mud saving apparatus of FIG. 1; and

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4.

The invention is shown in the drawings and will be described as used with a conventional "kelly." The apparatus of the invention may have utility, however, where a power swivel is employed and a conventional square or hex-type kelly joint is not employed. Therefore, "kelly." as referred to herein and in the claims, is intended to include the connection between a power swivel and the apparatus of this invention, which will be located between the power swivel and the drill pipe. The mud saving apparatus of this invention, as shown in FIG. 1, is installed between kelly 10 and pipe joint 11. Pipe joint 11 is the top joint in the pipe string (not shown) that extends downwardly into the well bore.

The apparatus includes tubular housing 12, which is made up of two sections, 12a and 12b. Section 12a is connected to the lower end of kelly 10 and the lower end of section 12b is connected to drill pipe 11. Thus, the housing may also serve as a kelly saver sub since, when breaking the connection between the kelly and the drill string, the connection between housing section 12b and drill pipe 11 will be the one that is broken. An additional kelly saver sub can be employed if desired between the lower end of housing section 12b and the drill pipe.

Located in housing 12 is valve element assembly 13. It includes elongated sleeve 14. The sleeve, preferably, is made of an elastomer, such as natural or synthetic rubber. Also, the sleeve may be reinforced, as by layer 15 of cotton duck. The sleeve is molded with a cylindrical opening in its upper end 14a. The opening tapers down to elongated slot 17 through lower end 14b of the sleeve. The wall thickness of the sleeve is substantially uniform throughout. Its exterior configuration is as shown in the drawings; a cylindrical shape at its upper end and flat-sided across its lower end. This can best be seen in FIGS. 4 and 5.

Means are provided to mount the sleeve in housing 12 with its upper end 14a held open so all fluid pumped through the kelly and housing 12 into the drill string will pass through the sleeve. In the embodiment shown, mounting ring 16 encircles upper end 14a. Preferably, the ring is bonded to the sleeve when the sleeve is molded. To improve the attachment between the elastomeric material of the sleeve and mounting ring 16, annular groove 18 is provided in the exterior of the ring. A plurality of spaced holes 20 extend through the mounting ring and intersect groove 18. This allows the elastomeric material of the sleeve to flow through openings 20 during the molding operation and fill up both the openings and annular groove 18 to provide a mechanical bond between the mounting ring and the sleeve.

Mounting ring 16 and, consequently, sleeve 14 is fixed and held in position in housing 12 by housing sections 12a and 12b. These two sections are connected together by threaded connection 22. Before this connection is made up, sleeve 14 is positioned in housing section 12b with mounting ring 16 resting on upwardly facing annular shoulder 28 on housing section 12b. The two housing sections are screwed together until lower end 26 of section 12a engages the mounting ring sufficiently to firmly hold mounting ring 16 between the lower end of housing section 12a and upwardly facing shoulder 28. The sleeve is molded with convex annular flange 30, which engage the lower end of housing section 12a, when the sleeve is mounted in the housing to provide a fluid seal between the upper end of the sleeve and the lower end of this housing section. This prevents fluid from bypassing the sleeve by flowing behind mounting ring 16. O-ring 32 seals the threaded connection between the housing sections to keep any fluid that may pass seal ring 30 from escaping through threaded connection 22.

Means are provided to resiliently urge the lower end of the sleeve closed with sufficient force to hold it closed against the hydrostatic head of the fluid in the kelly, when the kelly and housing are disconnected from the drill pipe. In the embodiment shown, leaf springs 34 and 36 are provided for this purpose. As best seen in FIGS. 2 and 4, the lower ends of the springs engage opposite sides of the slotted lower end of the sleeve and urge slot 17 closed. The lower ends of the springs are trifurcated, each having three fingers to engage the lower slotted end of the sleeve and spread the force exerted by the springs over substantially the length of the slot. In the drawings, slot 17 is shown open slightly even though springs 34 and 36 are in position to hold it closed. This was done to make the location and shape of the slot clear in the drawings.

The upper ends of the springs are attached to mounting ring 16. The connection between the springs and the mounting ring is best seen in FIGS. 3 and 5. Both springs are connected in the same manner, so only the connection between spring 36 and the mounting ring will be described in detail. The mounting ring is provided with vertical slot 40 into which the upper end of spring 36 extends. The spring has two vertically spaced mounting holes 37, which are in alignment with two vertically spaced tapped holes 38 in mounting ring 18. Mounting screws 42 extend through mounting holes 37 in the springs and threadedly engage the tapped holes in the mounting ring to attach the upper end of the spring to the mounting ring. The upper end of spring 34 is mounted in the same way in a slot in the mounting ring located diametrically opposite to slot 40.

The springs are designed to exert just enough force to hold the lower end of the sleeve closed against the hydrostatic pressure of the fluid that will exist in the kelly when the pumps are shut down preparatory to making a connection. Thus, the springs will exert little resistance to the forcing open of the lower end of the sleeve by the mud during normal circulating conditions. They will quickly close the lower end of the sleeve, however, as soon as circulation stops so that the kelly can be broken out of the drill string without delay and without the danger of losing any of the fluid still remaining in the kelly at the time circulation is stopped.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus and structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Claims

I claim:

1. In a drilling string through which drilling mud is pumped downwardly into a well bore including a plurality of pipe sections connected together with screw threads and a kelly connected to the upper end of the pipe string, the improvement in combination therewith of means for holding most of the drilling fluid in the kelly when the kelly is disconnected from the upper end of the pipe string, said means comprising a tubular housing connected in the drilling string between the bottom of the kelly and the top of the pipe sections and a valve element assembly located in the housing including an elongated sleeve of resilient elastomer material, means mounting the sleeve in the housing with its upper end held open so that drilling mud, as it is pumped downwardly through the kelly into the pipe sections below, will flow into the upper end of the sleeve, pass downwardly through the sleeve, and out the lower end of the sleeve, and means resiliently urging the lower end of the sleeve closed with sufficient force to hold the lower end closed against the hydrostatic head of the drilling mud in the kelly when the kelly and housing are disconnected from the pipe sections to keep the mud in the kelly from running out its lower end but which will allow the lower end of the sleeve to be forced open by pump pressure to permit normal circulation of mud to be maintained through the drilling string during drilling operations.

2. The mud saver apparatus of claim 1 in which the housing includes an upper and a lower section and the sleeve mounting means includes an annular member attached to the upper end of the sleeve to hold it open, said member being clamped between the upper and lower sections of the housing to hold the sleeve in place in the housing with its upper end held open by the annular member.

3. The mud saver apparatus of claim 2 in which the resilient means includes two elongated springs positioned on opposite sides of the sleeve, each spring having one end connected to the annular member and the other end engaging the lower end of the sleeve on the opposite side thereof from the other spring.

4. The mud saver apparatus of claim 3 in which the lower end of the sleeve is flat when closed.

5. The mud saver apparatus of claim 4 in which the springs are made of flat spring steel and have furcated lower ends to spread the force exerted by the springs on the lower end of the sleeve.