Oil well cementing plug

Application filed December 1, 1928. Serial No. 323,105.

This invention relates to a plug used in oil These objects together with other objects of well cementing as an indicator. In oil well corresponding accomplishments are obtained cementing, the well casing is commonly sealed by means of the embodiment of my invention - ^from ™e well hole side wall byintroduc- illustrated in the accompanying drawings :

Fig. 1 is. a conventional view of an oil ¢5 well hole with a casing therein and my improved plug in its initial arrested position, a portion of the casing being shown in elevation and a portion in section, the plug being shown in elevation; Fig. 2 is a plan view of eo the plug on an enlarged scale; Fig. 3 is a section as seen on the line 3—3 of Fig... 2 with parts in packing non-expanded position; and Fig. 4 is a fragmentary view in elevation similar to Fig. 3 showing the follower in pack- 65 ing expanded position.

Referring more particularly to the drawings, Figs. 1, 2 and 3 show the plug in packing non-expanded position. The well hole is marked 5 and disposed therein is a well cas- 70 ing 6 provided with the usual guide shoe 7 at the bottom thereof. At the bottom, collar 8 and indicator seat 9 are installed, the latter being a ring with port 10 extending therethrough. At the top of a casing is tight head 75 11 to which a pump line of pipe 12 is connected. A valve 13 is provided for shutting off pressure, if desired.

The well is cemented in the following manner : Mud is first introduced and circulated to 80 wash out slush. A tight head having a cement plug releasably retained in it is placed in position on the casing. Cement grout of a sufficient quantity is then pumped into the casing. The plug is indicated generally by 85 14 in Fig. 1. It is released upon the top of the column of cement grout. Mud is next pumped on top of the plug causing it and the column of cement grout to be forced downwardly through the guide shoe and around 00 the casing. When the plug engages the seat 9, its travel is arrested, and back pressure is developed which may be sufficient to stall the pump, indicating that the cement has reached its position for setting. With my improved 85 plug, the cement will be retained in this position, as the plug will maintain itself against

S ing cement into the casing and forcing it downwardly around the bottom and into the spa.ce between the casing and hole. It is then maintained in such position until the cement sets. Plugs have been currently used and 10 placed at the top of the introduced column of cement grout travelling therewith and acting as an indicator of the position of the column. This has been accomplished by pumping the column of grout into the casing ¹⁸ and causing the plug to be arrested in its travel when it reaches the lower end of the casing and by the arrest of its travel indicating through reaction to the pumping pressure,· that it has obtained its position. After 20 the plug has reached its lower position, it is the common practice to close’the upper end of the well casing and maintain the column of grout in position while setting takes place. Plugs have been employed which pack off the ²⁸ casing and are free to travel downwardly, but are restrained against upward movement so that retention of pressure on the top of the plug is not necessary to hold the column of cement grout in position and it is not neces⁸⁰ sary to maintain the top of the casing closed.

The present invention relates to a plug of the latter type. In such types of plugs, difficulty has been experienced in maintaining a leak tight packing and preventing the fluid on opposite sides of the plug from passing around the latter.

The objects of this invention are to provide a plug having any or all of the following ₄- features:

A packing which is automatically expanded by pressure of fluid from above; a plug having means to permit only one-way travel, namely, downward and provided with restraining means to prevent upward travel; and packing means arranged to be expanded upon upward pressure thereon when the plug is in its arrested position and which is main- ________₁______v___o__________ ____~ „ .........

tained in such packing position with an ex- upward movement. With the usuaffree pansive force acting on the packing in propor- movable plug, the valve 13 is closed to trap tion to the upward pressure exerted thereon, the liquid in the casing. Obviously a con- 1<X>

1,851,289 end so as to be longitudinally movable, said follower being arranged to be nested in said cup to expand the latter and being normally maintained in packing non-expanding position, and one-way gripping dogs secured to said follower to engage the well casing and prevent upward displacement.

2. A cementing plug for oil well casing comprising an elongated plug body, an outflaring tapered packing cup secured to and upstanding from said body at its upper end with its trailing edge directed upwardly, a follower secured to said body at its upper end so as to be longitudinally movable, said follower being arranged to be nested in said cup to expand the latter and being normally maintained in packing non-expanding position, pivoted gripping dogs secured to said follower to engage the well casing and prevent upward displacement, and spring means acting upon said dogs to hold the latter in contact with said casing.

3. A cementing plug for oil well casing comprising an elongated plug body, an outflaring tapered packing cup secured to and upstanding from said body at its upper end with its trailing edge directed upwardly, a follower secured to said body at its upper end so as to be longitudinally movable, said follower being arranged to be nested in said cup to expand the latter and being normally maintained in packing non-expanding position, and dogs pivotally mounted on said follower having arcmlte casing gripping surfaces eccentric to their pivotal axes so as to provide one-way gripping means and prevent upward displacement.

4. A cementing plug for oil well casing comprising an elongated plug body, an outflaring tapered packing cup secured to ana upstanding from said body at its upper end with its trailing edge directed upwardly, a follower secured to said body at its upper end so as to be longitudinally movable, said follower being arranged to be nested in said cup to expand the latter and being normally maintained in packing non-expanding position, dogs pivotally mounted on said follower having arcuate casing gripping surfaces eccen- _ trie to their pivotal axes so as to provide oneway gripping means and prevent upward displacement, and spring means acting upon said dogs to hold the latter in contact with the well casing. . . ₁₂₀

5. A cementing plug for oil well casing comprising an elongated plug body, an outflaring tapered packing cup secured to and upstanding from said body at its upper end with its trailing edge directed upwardly, a follower secured to said body at its upper end ¹²⁰so as to be longitudinally movable, resilient means disposed between said body and follower to normally maintain the latter in packing non-expanding position, dogs pivotally mounted on said follower and having siderable back pressure is developed tending to move the plug upward. .

My improved plug comprises a cylindrical body portion 15, which may be of wood or 5 any other suitable material. Attached to the bottom is a disk of rubber belting or the like 16 acting as a guide and also aiding in maintaining a leak tight fit with the casing. Attached to the body 15 at the upper end of 10 the plug is a .packing cup 17 having its trailing edge directed upwardly and preferably provided with a tapering outflaring wall. Upstanding from the body are guide posts 18 and slidably mounted thereon is a follower 15 19 to which is attached a plate 20. The cup is preferably made of rubber, the follower 19 of wood and the plate 20 may be of iron. Three posts are shown and mounted thereover between the follower and the body are 20 compression springs 21. These springs tend to normally maintain the follower out of contact with the cup or in cup non-expanding position. Ears 22 are provided on the plate and pivotally mounted between each ²⁵ pair of ears is a dog 23 having a toothed arcuate outer surface 24 which is eccentric to the pivotal axis 25 of the dog. Compression springs 26 are provided tending to maintain the dogs in their outer positions. If the fol30 lower is moved downwardly and nested within the cup, it will force the cup outwardly into expanded position.

The dogs are so arranged that there is a substantially free movement of the plug 35 downwardly until it reaches the seat 9. The outflaring cup as shown in Fig. 1, initially hugs the casing while the body of the plug is free. Thus, easy downward travel of the plug is permitted and pressure from above ⁴⁰ immediately expands the cup. Pressure of fluid from above tends to expand the cup to maintain a tight fit with the casing. After the cup has engaged the seat and the pump is stopped, pressure is relieved upon « the top of the plug. Thereupon, the pressure of the cement from below tends to move the plug upwardly. The follower is retained against movement due to the dogs engaging the well casing. In this position, the body ⁶⁰ is enabled to be moved upwardly so that the follower is moved into nested position with respect to the cup and the latter is expanded. The amount of expansion will depend upon the pressure from below. The casing is thus ⁶⁶ packed against the cement from below. T^beplug is allowed to remain in this position until cement has set, and thereafter the plug and cement within the casing are drilled out.