Patent Application
20090205728
Drilling chokes are used in several applications to control the flow of production medium or drilling fluids. For example, well control for circulating a “kick” or underbalanced and near balanced drilling applications often require the use of one or more drilling chokes to improve rig site safety. In addition, drilling chokes are useful for conventional well control issues involving exploration wells and drilling over-pressured zones, well testing operations and well clean ups which require flow control of the wellbore fluid to produce reliable test results. The typical drilling choke system includes a drilling choke 100A, such as illustrated in
The front and back discs 150/160 each have machined-through bores 152/162, respectively, and are positioned in holders 154/164. Drilling fluid passes through inlet 112 into the choke's housing 110 and passes a profiled throttling stem 120 holding the discs 150/160 together against a lower holder 164. The throttling stem 120 can be operated to rotate the front disc 150 relative to the stationary back disc 160, thereby determining the orifice size through the bores 152/162 and throttling fluid flow through the choke 100A.
The fluid throttled through the discs 150/160 can have abrasive materials such as rock, cuttings, sand, etc. and can have a high flow rate so that the fluid erodes the disc material. Moreover, the throttled fluid exiting the stationary back disc 160 forms a turbulent flow pattern that erodes the internal components of the outlet spool 130 beyond the discs 150/160 by cavitation and abrasion. The erosion can eventually lead to costly repairs and the need to replace components. Therefore, operators typical line the outlet spool 130 with a number of tungsten carbide sleeves 132 to handle erosion. These wear sleeves 132 can be costly and may need repeated replacement.
In alternative arrangements, a drilling or production choke 100B as in
A drilling choke 200 illustrated in
The back disc 400 has an annulus seal 430 near its front face 402 and has an annulus trash seal 440 near its back face 404. These seals 430 and 440 engage the inner wall of the outlet spool 230. The annulus seal 430 can be a spring type seal having elastomer and metal springs and can be used to hold pressure around the disc 400. The annulus trash seal 440 can be an elastomer O-ring having polymer back up (par-bak) rings and can used to keep debris from fouling the seal area and caking between the disc 400 and spool 230.
Advantageously, the discs 300/400 can install in existing drilling choke or valve housings and outlet spools that use conventionally shaped discs without the need for specifically modifying the choke's housing or outlet spool to accommodate them. In particular, these discs 300/400 are shown in
In addition to these advantages, features of the discs 300/400 discussed in more detail below can eliminate the need for all or most of the tungsten carbide liners typically required for the outlet spool (see e.g., inserts 132 in
During operation of the choke 200, high velocity and abrasive drilling fluid passes through inlet conduit 212 into the choke's housing 210 and passes the throttling stem 220 holding the discs 300/400 together against lower holder 270. The throttling stem 220 operated either manually or automatically rotates the front disc 300 relative to the back disc 400 and determines the orifice size through the bores 310/410, thereby throttling the flow of drilling fluid through the choke 200.
The rotatable front disc 300 shown in detail in
In general, the discs 300/400 can be composed of a metallic material, non-metallic, or ceramic material and, for example, can be composed of tungsten carbide. In addition, the front and back discs 300/400 both have the same diameter D1, although this may not be strictly necessary in some implementations. As opposed to the conventional disc arrangements, the back disc 400 has a length L2 that is greater than the front disc 300's length L1. For example, the back disc 400's length L2 can be at least twice that of the front disc 300. In this way, the back disc 400's length L2 can be at least approximately 6/10ths of its diameter D1, while the front disc 300's length L1 can be at least approximately 3/10ths of the diameter D1. Alternatively, the back disc 400's length L2 can be even greater. For example, the entire length of the front and back discs 300/400 combined can be about at least 6 times the diameter of the chokes bore.
On the front disc 300, the tapered reliefs 312 in the bores 310 can define an angle θ relative to an axis through the bores 310, and the tapered reliefs 312 can extend a distance H in the bores 310. The relative dimensions of the discs 300/400, bores 310/410, and reliefs 312 may vary depending on the implementation, the size of the choke 200, the type of medium and flow rates expected, etc.
In one particular example, the front and back disc's diameter D1 can be 4-inches, but it is understood that this dimension as well as the other dimensions discussed in the example herein depend on the choke or vale bore size, body cavity, flow medium, desired flow restriction, etc. Continuing with this example, the rims 306/406 can extend to a diameter D2of about 5-inches. Each of the bores 310/410 can be about 1-inch in diameter, but in general can be of any diameter from about 0.125 or greater. The front disc 300's length L1 can be 1.5-inches (i.e., 3/10th of the disc's diameter D1), while the back disc 400's length L1 can be about 3-inches or greater (i.e., two times or greater than that of the front disc 300). In this example, the angle θ for the tapered reliefs 312 can be about 30-degree angle plus or minus and can extend the distance H of about 0.5-inches into the bores 310 (i.e., about one-third of the front disc 300's length L1). Again, each of these dimensions is provided for illustrative purposes and actual values can depend on the particular implementation and other factors. Moreover, each of these dimensions can vary plus or minus within acceptable tolerances.
When the discs 300/400 are used to throttle drilling fluid through the choke 200, the front disc's tapered reliefs 312 help to funnel the high velocity and abrasive drilling fluid into the bores 310 and helps minimize material erosion by allowing the drilling fluid to enter the bores 310 at an angle rather than at a sharp edge. The stationary disc 400's increased length L2 extends the bores 410 and minimizes the exiting angle of the fluid flow from the back face 404, thus reducing the flow energy and turbulence produced in the housing (210;
Although the front and back discs 300/400 have been disclosed as having a pair of bores 310/410 each, it will be appreciated that other implementations may use discs 300/400 having one bore, a pair of bores, or more than two bores in both discs 300/400 or that one disc may have more or less bores than the other disc. Although the front and back discs 300/400 have been disclosed for use in a drilling choke 200, it will be appreciated that the discs can be used in any application where rotating discs are used to throttle a medium through any various type of choke or valve, including, but not limited to, drilling or production chokes or valves. Within the choke 200 itself, other devices such as a cylindrical throttling member that engages outer edges of the rotatable disc 300 can be used for rotating the disc 300 as opposed to the throttling stem 220 described above that engages the disc 300's center. In addition, the throttling stem 220 of
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
