Patent Application
20180112654
Ball and sleeve plungers are widely used in oilfield. These systems are commonly used in gas flowing wells. In gas flowing wells it is essential to move fluid as well as gas to the surface to keep the wells flowing. If a sufficient amount of liquid is not moved out of the well, the resulting column height of the fluid from the bottom of the well builds a pressure too great for the formation pressure to overcome. This created equilibrium is known as “loading up” or the “logging off” of a hydrocarbon well.
The ball and sleeve plunger system, as described in U.S. Pat. No. 8,181,706, solves this problem by bringing certain volumes of liquid to surface as well as allowing a certain volume of gas to escape in a set ratio. The ball and sleeve plunger accomplishes this by using a hollowed sleeve with an outer diameter similar to the inner diameter of the tubing and an inner diameter matching the diameter of a free piston, a simple ball. The lower portion of the sleeve's opening begins larger than or equal to the diameter of the free piston but bevels down to a smaller diameter. The free piston's diameter in substantially less than that of the tubing, meaning that gravity is able to move a free piston (commonly made of steel) beneath the column of fluid. Once the sleeve is released at the top of the tubing, it too moves past the column of fluid and mates with free piston. Formation pressure, greater than the sum of the fluid pressure, local atmospheric pressure and weight of the ball and sleeve, is then applied beneath the sleeve and ball combination and lifts the duo as well as the column of fluid. The fluid exits the orifice at the well head, while the sleeve and ball combination meets a separator rod. The separator rod is concentric with and smaller than the inner diameter of the sleeve. When the sleeve and ball combination is forced into the separator rod, the free piston is dislodged from the sleeve and allowed to fall back down the tubing. The sleeve is held on the separator rod by the drag force of the gas passing by on its way out the wellhead. The sleeve is held at this position for a predetermined time and is then released back down the tubing to complete the cycle. The sleeve is released by equalizing the formation pressure and thus ceasing gas flow.
Problems have arisen for this system in aging wells. When hydrocarbon wells are continually produced the formation pressure, the pressure actuating the production process, starts to deplete. Less formation pressure results in a lower velocity of the sleeve and ball combination when it meets the separating rod. The velocity of the sleeve and ball combination becomes especially important when common well residues accumulate on the inside surface of the sleeve. If the minimum velocity to push the sleeve completely past the tip of and on to the separator rod is not met, a seizing of the sleeve is likely. With the sleeve is seized on the separator rod the cycle is halted. This halt in cycle is a cease of production and an overall loss of revenue.
Adaptations have been made to the separator rod to combat residue accumulation but have failed in creating substantial progress. A possible variable explaining this result is the stagnation of the sleeve experienced while in its position on the separator rod. With the sleeve at rest, residue carried by the gas flowing around the sleeve can jam itself into the tolerances between the sleeve and separating rod. This situation can also cause the seizing of sleeve and interruption of the cycle.
The present invention seeks to provide a solution to this problem by providing one or more spherical channel(s) recessed into the separating rod. The separating rod typically consists of cylindrical bar stock made of steel or other alloys. The profile of the separating rod includes a cylinder of consistent or fluctuating diameter. The spherical channel(s) act in shearing the accumulation of residues on the inside surface of the sleeve and keeps the sleeve from becoming stagnant in its top position.
The shearing of residue accumulation may be in two sets of shearing actions. The first shearing action would be during any point of the cycle in which the sleeve is passing over the separator rod. This includes the arrival or departure of the sleeve during each cycle. This action is due to the upper and lower edges of the recessed channel(s) being, depending on the spherical angle, somewhat perpendicular to the motion of the sleeve. This attribute results in the edges of the channel(s) acting as a shearing face with the recessed portion acting as clearance for dislodged residue. The dislodged residue is then carried up the channel and out the wellhead. The second shearing action is introduced while the sleeve rotates on the separator rod. While the sleeve rotates (rotation mechanics are discussed below) on the separator rod, any remaining residue on the inner face of the sleeve is sheared off. This attribute occurs due to the edges of the channel(s) being, depending on the spherical angle, somewhat perpendicular to the rotation of the inner face of the sleeve.
The rotation of the sleeve may be due to the dispersion and direction influences of the passing gases over and through the channels. The feature of the channel wrapping around the separation rod may act in dispersing the passing gas on the inside face of the sleeve. This element of the design may cause the sleeve to rest on a cushion of passing air and thereby reducing friction between the inside face of the sleeve and the separator rod. This attribute also may cause the generation of a component of the gas flow direction to be perpendicular to the inner face of the sleeve. Having a perpendicular component of gas current passing over the inner face of the sleeve may create drag and thusly creating a moment about the center of the sleeve. Even with small rotation moments, the rotational motion may be possible due to the low amount of friction opposing it. In addition, rotation of the sleeve reduces the possibility of residues, carried by passing gas currents, from lodging themselves into the tolerances between the sleeve inner face and the separator rod. In addition, if any gas carried residue becomes lodged it would then be subsequently sheared off by the opposing channel edge.
For the purpose of this disclosure, the term “plunger” will refer to the combination of the free piston mated with the inner hollow passage of the sleeve. The term “downhole” will refer to the portion of the hydrocarbon well beneath the well head. The term “residue” will refer to residue and debris involved in the drilling, completion and production of hydrocarbon wells (e.g. fracking sands, coalbed residues, paraffin, etc.).
The following description of one embodiment of the present invention is intended to show the value and use of said invention to someone skilled in the pertaining art. The present invention includes but is not limited to the following features disclosed.
The present invention in this example embodiment has a linear bevel tip profile 4 that may aid in the concentric alignment of the sleeve inner face and penetration of residue accumulation on said surface. Spherical channels 2 on the tip profile 4 may begin the act of shearing residue accumulation, which gives the sleeve 38 clearance to proceed up the separator rod body 1. The tip 5 is the portion that contacts with the free piston 40 during decoupling of the plunger. The tip 5 has a diameter, preferably, small enough to effectively penetrate residue accumulation but large enough to supply a surface area able to receive the free piston 40 impact without permanent strain. The decoupled sleeve 38 travels up the separator rod body 1 to the portion with the smallest tolerance between the inner face and the separator rod body 1. At this point, the upper channel edge 7 may shear the residue accumulation on the inner face of the sleeve 38 as it travels to the sleeve stop 5. Once the sleeve 38 has reached the vertical limit of the sleeve stop 5, the passing gas current may be dispersed on the inner face of the sleeve 38. This gas dispersion in the tolerance of the inside of the sleeve 38 and separator rod body 1 may reduce friction. The passing gas current may also experience an influence in direction, giving the current direction a component perpendicular to the sleeve 38 inner face. A gas current with a direction component perpendicular to the sleeve 38 inner face may cause a drag force capable of rotating the sleeve 38 on the previously described low friction interface. This rotation may cause remaining residue accumulation and gas current carried residue to shear off on the lower channel edge 8. Clearance created by spherical channel may allow a passage for said residues to escape propelled by passing gas currents. Once the gas flow period ends and the sleeve 38 is allowed to descend back over the separator rod body 1, any remaining residue may be sheared off by contact with the lower channel edge 8. During the rotation, ascent and descent of the sleeve 38 the angle of contact between the inner face of the sleeve 38 and the upper channel edge 7, as well as the lower channel edge 8, is dependent upon the spherical angle 6. Optimization of the sleeve 38 rotation, residue shearing and gas dispersion may be adjusted with the amount of spherical angle 6.
