Well cementing apparatus
United States Patent 2368419

This invention is concerned with the controlled passage of cementitious slurry or other fluids through a well casing or liner for delivery at any specified or predetermined point within a well bore. In a more limited sense, the invention is directed to apparatus for determining the deposition...

Mcgivern, Paul V.
Joe, Chastain
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137/67, 166/289
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This invention is concerned with the controlled passage of cementitious slurry or other fluids through a well casing or liner for delivery at any specified or predetermined point within a well bore. In a more limited sense, the invention is directed to apparatus for determining the deposition of cement in the annular space between the wall of the well bore and the casing or liner disposed therewithin.

It is a common practice to cement a string of' casing within a well bore for the purpose of obtaining a water shut-off. In deep wells, where the casing is of great length, it is preferred not to pump all of the cement through the entire casing string for upward passage behind the casing, because of the high final pump pressures necessary to raise the heavy cement column to the desired elevation. The time consumed in completely displacing the large quantity of slurry required. is of such extent as to enable quick setting cements to thicken appreciably and increase their resistance to passage through the casing and the \annular space between it and the wall of the bore.

These difficulties can be avoided or minimized by' following multiple-stage cementing procedure, consisting of ejecting separate charges of cement through sequentially opened ports or outlets located at predetermined and vertically spaced points in the casing.

Casing strings embodying vertically -spaced ports also are used in placing cement above and below a productive zone, and between the productive formations of a multiple zone well. By this device, each zone can be isolated, and any, waters present prevented from encroaching on the productive formations. Similarly, cement slurry can be spotted through vertically spaced casing ports adjacent intermediate waters occurring at intervals along the well bore, the ce-, ment serving to shut off these waters without the need for providing a continuous seal behind the casing string throughout its entire length.

It is an object of the present invention to open normally closed outlets in a casing string by the action of chemical substances on elements forming closures for such outlets.

Another object of the invention is to provide a casing apparatus having ports or outlets closed by elements which can be disintegrated or dissolved by solvents preferably having no deleterious effects upon the casing itself.

This invention has other objects which will become apparent from a consideration of the embodiment shown in the drawing accompanying and forming 'part of the present specification.

This form will now be described in detail, but it. is to be understood that such detailed description is not to be taken in a limited sense, since the scope of the invention is best defined by the Sclaims appended hereto.

Referring to the drawing: Figure 1 is a longitudinal section through a string of well casing, illustrating an embodiment of the invention; Figure 2 is an enlarged longitudinal section of one of the casing collars shown in Figure 1; and Figure 3 is a partial side elevation of the collar as seen in the direction of arrow 3 in Figure 2.

In its general apsects, the invention contemplates an apparatus forming a component part of a casing string by being embodied therein at one or several predetermined points along its length. The apparatus includes one or more ports or outlets initially held closed by closure members consisting of a substance which can be dissolved or disintegrated upon coming in contact with a suitable solvent. The outlets are normally held closed by these members to permit downward passage of suitable fluid, as cement slurry, past the apparatus to a lower point in the casing from where such fluid is ejected into the surrounding bore. After the operation at the lower point has been completed, a suitable solvent is spotted Sin contact with the closure members to produce their disintegration or dissolution, after which the desired cementing or. other operation through the opened ports or outlets can occur.

A specific application of the invention is shown in Figure 1. A collar A or B is incorporated in a string of casing by being threadedly or otherwise coupled to adjoining casing sections C. This collar has a plurality of circularly spaced ports or outlets 10 for establishing communication beStween its exterior and interior. However, these outlets are initially held closed by generally cylindrical plugs 11, each of which has a reduced portion 12 fitting within the inner part 13 of the casing outlet, and an enlarged outer portion forming a boss 14 engaging the base 15 of an inclined groove .16 milled or otherwise formed in the exterior of the collar. By causing the boss to abut the base of the groove, the plug is unable to move inwardly, its outward displacement under the pressure action of fluid within the casing being prevented by its contact with a baffle plate IT extending partially lengthwise of the groove and held snugly against the plug by welding material 18. It is to be noted that the outer portion 19 of the outlet is inclined to the Vertical by being formed between the inclined groove 16 and baffle plate 17, so that the fluid ejected from the outlet is given a "whirling" motion, ensuring the formation of a proper, channel-free seal between the casing and the wall of the bore.

When employed in the cementing of a well, the collar A or B with the soluble plugs I I in its outlets is lowered into the bore as an integral part of the casing string C. If the casing is to be cemented in the bore, the proper amount of slurry is pumped down the casing past the soluble plugs for ejection from the casing shoe (not shown) and for upward passage into and through the annular space between the casing and the wall of the bore. After this operation has been completed, a string of tubing 20 is run into the casing Until its outlet 21 is adjacent or in the vicinity of the soluble plugs in the collar. A suitable solvent 22 is then pumped down the tubing and into contact with the plugs to produce their dissolution or disintegration.

The material of the plugs I is such as to be dissolved or disintegrated by a substance having substantially no chemical or deleterious action upon the casing itself. As an example, the plugs can be made from magnesium, and the solvent can consist of a ten or fifteen percent corrosion inhibited solution of hydrochloric acid pumped down the tubing for action upon the plugs. This acid will have no effect upon the casing, but it will disintegrate the plugs by its chemical action, and free the openings 10 through the collar to allow passage of fluid therethrough. The fact that the outlets are free of obstructions or restrictions will become apparent at the surface of the bore upon obtaining fluid returns around the casing. With the outlets open, the solvent is preferably circulated from the bore and the required amount of slurry pumped down the casing and through the outlets 10.

While specific mention has been made of the use of magnesium as material for the plugs, and hydrochloric acid as a chemical agent for their disintegration, it is to be understood that many other materials can be employed so long as they are removable by chemical action, and preferably without any material harm being done to the casing. For example, the plugs can be formed of aluminum or an aluminum alloy, which is readily attacked by a solution of sodium hydroxide.

When used for multiple stage cementing purposes with two or more upper stages, collars A.

B embodying the soluble plugs If are placed at predetermined points in the casing string C. As many of these collars can be employed as is believed to be necessary, depending upon the length of the casing. The completely made up casing string with the customary shoe at its lower end is run in the bore. In the usual situation, the collar outlets 10 are closed by the soluble plugs It, but the outlet through the shoe is open. By the use of a suitable method of cementing, as the plug method, a predetermined amount of cement is placed through the shoe (not shown) and behind the casing. Thereafter, tubing 20 is lowered through the casing until its outlet 21 is adjacent the first stage collar A positioned above the shoe. The proper amount of chemical solution 22 is pumped down the tubing to the region of the collar A and permitted to remain in this position until it. has dissolved the plugs If and opened the collar outlets 10.

Mud or other fluid Is then circulated down the tubing or casing and through the outlets to remove the solvent and resulting solute to the sur- 7 face of the bore. Thereafter, a measured amount of cement slurry is pumped down the casing between top and bottom plugs 23, 24, the bottom plug 24 stopping immediately below the open casing outlets 10 and continued downward movement of the top plug 23 ejecting cement through these outlets and through the baffled inclined grooves 16, which cause the slurry to "whirl" as it passes upwardly through the annular space between the casing exterior and the wall of the bore. In lieu of the plug method, the cement slurry can be pumped through the tubing 20, or pumped through a packer set above the outlets 10 in the lower collar A.

After the cementing operation through the lower stage A has been completed, the tubing string 20 is positioned with its outlet 21 adjacent the next higher stage B, and the chemical solution 22 pumped through the tubing and into contact with the plugs I in this stage collar. These plugs or closures are dissolved, the chemical substance circulated from the hole as before, and the proper quantity of cement pumped down the casing and ejected through the open ports 10 in the upper stage B to fill the annular space between the casing and the wall of the bore. This cycle 'of operation can be continued in an upward sequence throughout the entire length of the casing depending upon the number of stage collars employed therein.

In the event that the casing is only to be cemented in the well bore at intervals along its length, as in separating producing zones or shutting off intermediate waters, a "Petal" basket 25 is secured to the casing immediately below each collar A or B, with the outer portions of its leaves 26 engageable with the wall of the hole.

The collar outlets 10 are opened by dissolving the plugs as before, but the cement slurry ejected through these openings will be unable to flow below the basket 25, which serves as a bridge and confines the cement to the intended length of casing along which a cementitious seal is to be formed.

The casing assembly embodying the collars A or B also finds employment in connection with wells having a plurality of producing horizons.

The casing string C is run in the well with one or more of the collars A, B incorporated therein at predetermined and vertically spaced points so as to be .positioned adjacent respective producing zones.

Production may be obtained initially from a zone above or below the collars. Upon exhausting of this first zone, a suitable solvent is placed adjacent one of the collars, such as B, opposite another producing horizon for the purpose of dissolving the collar discs or plugs 1 and opening its outlets 10 to the passage of production into the casing from the second zone. When the second zone is depleted, the outlets 10 in the next collar A are opened through dissolution of its discs 11, and production obtained from this third zone or horizon. As many collars can be incorporated at predetermined points in the casing string as there are producing zones and each zone opened to production at any time and in any sequence by spotting acid, or any other suitable solvent, in contact with the soluble closure 0r plugs. The solvent can be placed by the tubing method, described above, or through the employment of various other methods, among which is the confining of the solvent within a bottle or frangible container which is lowered 5 on a wire line to the region of a collar and then broken by dropping a weight or by striking with a bailer to free the solvent for action upon the discs.

We claim: 1. A cementing device, including a tubular member having a lateral outlet opening, a soluble plug in said outlet closing said outlet opening, and a baffle over said outlet opening securing said plug therewithin, said baffle directing fluid issuing from said outlet opening upon dissolving of said plug.

2. A cementing device, including a tubular member having one or more outlets through its side wall, respective grooves in the exterior of said member, communicating with said outlets, a soluble plug in each outlet, and respective baffles within said grooves overlying said outlets and engageable with the plugs to prevent their displacement from said outlets, said baffles directing fluid issuing from said outlets upon dissolving of said plugs.