US3461958A - Methods and apparatus for installation and removal of preventer stacks in offshore oil and gas wells - Google Patents

Description

0. BROWN 3,461,958 ION AND' REMOVAL OF WELLS Aug. 19, 1969 c METHODS AND APPARATUS FOR INSTALLAT PREVENTER STACKS 1n OFFSHORE OIL Filed Jan. 16, 196'? AND GAS s Sheets- -Sheet 1 K o 8 o ATZTORM'] 3,461,958 N AND REMOVAL OF OFFSHORE OIL AND G Aug. 19,1969

C C. BROWN METHODS AND APPARATUS FOR INSTALLA'I'IO PREVENTER STAGKS IN AS WELLS Filed Jan. 16. 196'? s Sheets-Sheet 2 AZTORNE) Aug. 19, 1969 I METHODS AND APPARATUS mavsmzn s'rAcKs m o C C. BROWN Filed Jan. 16. 1967 FOR INSTALLATION AND REMOVAL OF FFSHORE OIL AND GAS WELLS 6 Sheets-Sheet 5 ATTORN/fj c c. BROWN 3,461,958

TION AND REMOVAL OF Aug. 19, 1969 METHODS AND APPARATUS FOR INSTALLA PREVENTER STACKS IN OFFSHORE OIL AND GAS WELLS Filed Jan. 1 s. 1967- s Sheets-Sheet 4 Z 2 i VA 7 f L M HU ML a E. \t w z W a. 5 z 2 in; m w m a M w w w m, w ll! a a M a fv ll'l V.

'6 Sheets-Sheet 5 C C. BROWN -PREVEN'IER STACKS IN OFFSHORE OIL AND GAS WELLS METHODS AND APPARATUS FOR INSTALLATION AND REMOVAL OF Filed Jan. 16. 196'! Aug. 19, 1969 c Q 3,461,958

METHODS AND APPARATUS FOR INSTALLATION AND REMOVAL OF PREVENTER STACKS IN OFF WELLS Filed Jan. 16. 1967 6 Sheets-Sheet 6 SHORE 011, ND GAS ATTORNEY United States Patent METHODS AND APPARATUS FOR INSTALLATION AND REMOVAL OF PREVENTER STACKS DI OFFSHORE OIL AND GAS WELLS Cicero C. Brown, Brown Oil Tools, Inc., P.0. Box 19236, Houston, Tex. 77024 Filed Jan. 16, 1967, Ser. No. 609,572 Int. Cl. E21b 33/035, 33/06 US. Cl. 166.5 Claims ABSTRACT OF THE DISCLOSURE Summary of problem and invention This invention relates to a method and means for installing preventer stacks in underwater wells for ease of removal, and further relates to a method and means providing recovery of preventer stacks and associated apparatus.

It is readily apparent that drilling oil and gas wells is an' expensive proposition, and this is especially true in offshore operations. One way of holding the cost of drilling operations to a minimum is the recovery of as much equipment installed in or at the drilling site as possible, and especially so in recovering the more expensive apparatus used in offshore operations. One of the more expensive items required in drilling oil and gas wells is the stack of blowout preventers. Blowout preventers are installed at the well head to limit upward flow through the well bore and also to prevent upward movement of the drill string should the drill bit enter a formation having exceedingly high internal pressures. High pressure formations suddenly penetrated by the well bore have ejected the drill string upwardly through the well head to cause substantial damage to the drilling equipment and serious injuries to the personnel. The problem is also present in drilling operations in offshore locations where the preventer stack is installed beneath the body of water at the well head.

In all drilling operations, the drilling operation is eventually terminated and the blowout preventers are removed from the well. This is true whether the well is a dry hoe or provides oil in substantial quantities. The method of removing blowout preventers from the offshore wells has been less than successful. The preventer stack is customarily joined to the casing and a protector casing placed about the casing string. In view of the substantial length of protecter casings, and in further view of the fact that the well casing extends several thousand feet in the well, the preventer stack is usually firmly cemented in place and difiicult to recover.

One method found in the prior art requires upward lifting forces on the preventer stack to free the preventer stack from the casing and the preventer casing which are 3,461,958 Patented Aug. 19., 1969 "ice cemented in place. In view of the limitations of the prior art, the present invention may be summarized as providing a pressure fluid expansion chamber below the preventer stack for lifting the stack from the well on admission of pressure fluid through the well casing. The chamber is not used until the preventer stack is no longer needed at which time fluid communication between the well head and chamber is established. Pressure fluid in the chamber acts against a surface to lift the preventer stack. The chamber expands by use of a sliding seal permitting continued admission of pressure fluid to substantially lift the appendages to the preventer stack free of the well. With the present summary in view, it is, therefore, an object of the present invention to provide a method of installing and removing preventer stacks in underwater wells in which the separation of the preventer stack from the casing is achieved by pressure fluid lifting the preventer stack.

A related object of the present invention is to provide a new and improved apparatus for recovery of preventer stacks from underwater wells wherein the drilling vessel lifts only the preventer stack and is not used to free the frictional engagement of the cement jacket with the well bore.

One object of the present invention is to provide a new and improved method for installing and removing preventer stacks in underwater wells wherein separation between the preventer stack and well casing is achieved by disconnection as opposed to rupture of the well casing and cement jacket.

Yet another object of the present invention is to provide a new and improved method for recovering preventer stacks from underwater wells wherein movements against substantial friction between the cement jacket and the well bore is achieved by hydraulic pressure supplied to the well to lift the preventer stack.

One object of the present invention is to provide a new and improved method of retrieving preventer stacks in which the annulus between the protector casing and well casing is used as an expansion chamber for lifting the preventer stack from below to avoid damage to the expensive apparatus.

Yet another object of the present invention is to provide a new and improved method of removing preventer stacks from underwater wells in which the installation is effected with a view of easy removal without interfering with the function of the blowout preventers or drilling of the well.

One object of the present invention is to provide a new and improved apparatus for removing installed blowout preventers from underwater wells which incorporates means for freeing the well casing from the preventer stack and thereafter uses a chamber for receiving pressure fluid to lift the preventer stack from the well.

Other objects and advantages of the present invention will become more readily apparent from a consideration of the specification and drawings wherein:

FIG. 1 is a longitudinal sectional view of the apparatus of the present invention during assembly on a drilling vessel before placement in the well bore;

FIG. 2 is a longitudinal sectional view similar to FIG. 1 after assembly and prior to placement in a well bore;

FIG. 3 is a longitudinal sectional view of the apparatus shown in FIGS. 1 and 2 after cementing in the well bore which further illustrates operation of a tool to separate the casing from the preventer stack;

FIG. 4 is a view similar to FIG. 3 showing the step of separating the casing from the preventer stack and further illustrating pressure fluid flow for lifting the preventer stack;

FIG. 5 is a view similar to FIG. 4 illustrating completion of the step of lifting the preventer stack;

FIG. 6 is similar to the step shown in FIG. 3 and also illustrates an alternative embodiment of the present invention;

FIG. 7 illustrates an additional step in the method using the embodiment shown in FIG. 6;

FIG. 8 is a sectional view of an additional embodiment of the present invention showing use of an inside cutter for separating the preventer stack from the well casing;

FIG. 9 is similar to FIG. 8 and illustrates separation of the preventer stack from the well casing;

FIG. 10 illustrates an additional embodiment of the present invention; and

FIG. 11 is a view similar to FIG. 10 illustrating the preventer stack during the step of lifting the preventer stack while the protector casing remains in the cemented Well bore.

Attention is first directed to FIGS. 1-5, inclusive, which illustrate the method and apparatus of the present invention in detail. The apparatus associated with FIGS. 1-5 will be first described, and thereafter, the steps of the method of the present invention will be also related, particularly with reference to the drawings which illustrate various steps in the method. Therefore, attention is first directed to FIG. 1 of the drawings which illustrates the apparatus in a state of assembly prior to installation in a well bore.

In FIG. 1, a joint of casing 12 is preferably integrally joined to a tubular connector 11 for use in making up the casing string to be placed in the well bore (not shown). The connector 11 is held in a predetermined position by resting a flange 13 on a removable support 10, the support 10 customarily located on the drilling barge or vessel in the water near the drilling site of the well.

Aboard the drilling vessel, the upper portions of the well casing string are assembled relative to the protector casing as will be described. In further particular, a base member 16 serves as mounting means for the blow-out preventers 20 which are located thereabove and as a support for a casing member 12a suspended therebelow. Positioned concentrically about the casing member 12a is a protector casing which is somewhat greater in length than the casing 12a.

In drilling oil and gas wells located beneath bodies of water, the protector casing 15 length is varied over a wide range depending on the conditions encountered. Thus, for instance, the preventer casing may be relatively short should solid, non-porous geological strata be encountered. The members 12a and 15 are arranged concentrically of one another and have a length best determined by conditions at the drilling site.

Considering the blow-out preventers further, attention is directed to FIGS. 1 and 2 which illustrate the preventers secured to the upper side of the base plate 16. In the drawings, the preventer stack is secured to the base plate by conventional bolts 20a and a seal member is placed interiorly of the bolts 20a for maintaining a pressure tight seal. The rams of the preventer stack are represented generically in the drawings as will be understood by those skilled in the art.

Attention is next directed to the means indicated generally at 18 at the lower end of the casing member 12a which comprises a male connector means for releasable connection with the tubular member 11. A setting sleeve 22 is threaded into the lower end of the casing member 12a, it being noted that the casing member is somewhat enlarged at the threaded connection whereby the setting sleeve is equal in inside diameter to the casing member 12a and the connector member 11 therebelow. The setting sleeve 22 incorporates conventional seal means at both 4 ends thereof to provide integrity of fluid communication through the well casing string. Of particular interest is the expander ring 23 adjacent the setting sleeve which is in a relaxed condition in FIG 1. Use of the expander ring 23 will be noted in greater detail hereinafter.

Attention is next directed to the tubular connector means 11 engaged with the male connector means 18. The means 11 incorporates the outwardly extending shoulder means 11a for engaging additional means placed within the protector casing 15 as will be described. An internal recess 11b is provided within the connector means 11 for receiving the expander ring 23. A sealing surface 11c within the connector is provided for engaging the seal member on the setting sleeve 22 to maintain fluid communications through the well casing string. Additional details concerning the female connector member 11 will be noted hereinafter.

Attention is next directed to the apparatus carried within the protector casing 15 and engaging the shoulder 11a on the connector member 11. Attention is first directed to the encircling resilient cup 28 which is held in position by a support ring 29. The support ring 29 is carried by the shoulder 11a on upward movement of the shoulder relative to the protector casing 15 whereby the rubber ring 28 is sealed against the interior wall of the member 15. A retainer ring 15a is engaged at the loWer end of the protector casing 15 for initially inserting the seal cup 28 within the casing member 15. The ring 15a is threaded to the interior of the casing member 15.

It should be noted that the foregoing description is directed to the details of construction of the apparatus shown arranged in FIG. 1. However, the apparatus of FIG. 1 is also illustrated in FIGS. 2-5, inclusive, during various stages in the practice of the method of the present invention. Relying on the foregoing description of the apparatus, attention is next directed to FIGS. 1-5 for an understanding of the method of the present invention. FIG. 1 illustrates the assembly stage of the present method. The setting sleeve 22 is threaded to the lower end of the casing member 12a and thereafter the protector casing 15 is positioned in the concentric relationship illustrated in the drawings relative to the casing 12. The cup 28 is placed within the protector casing 15 and the retainer member 29 is inserted thereafter and the two members are locked within the protector casing by the retainer ring 15a. The female connector means 11 is placed in protector casing 15 about the setting sleeve 22 as shown in FIG. 1. Upward movement of the shoulder 11a urges the support ring 29 and the rubber cup 28 to the illustrated position of FIG. 1 wherein the female connector is positioned for later engagement with the male connector.

Attention is next directed to FIG. 2 of the drawings which illustrates the step of the present method wherein the tubular connector 12a which carries the preventer stack 20 is joined to the casing string 12. A torque-wrench 34 is inserted through the preventer stack 20 and positioned adjacent the setting sleeve and engaged therewith. The setting sleeve is preferably provided with left-hand threads engaging interior threads of the connector means 18. The setting sleeve fully threads against an abutting shoulder 18a illustrated in FIG. 2.

Attention is next directed to the expander ring 23 which is in the expanded position in FIG. 2. The expander ring 23 is forced into the internal recess 11b of the female connector means 11 which is positioned adjacent the expander ring, the extreme end 18b of the tubular member 18 moving beneath the ring to expand it into the recess 11b. It will be noted that the two portions of the casing string, the members 11 and 18 in particular, have been joined to one another by the expander ring 23. Reference is made to the fact that the recess 11b is defined by a pair of facing shoulders which lock the expander ring 23 in place.

In the assembly step shown in FIG. 2, it should be noted that the connccter members 11 and 18 are moved axially toward one another by threaded engagement with the setting sleeve 22. The movement contacts the flanges 13 carried on the connecter 11 against the open lower end of the casing 15 and provides an adequate seal to prevent intrusion of materials under pressure into the annulus between the two casing members.

At this juncture, the support member is removed and the preventer stack, including the casing 12, is inserted into the hole drilled beneath the drilling platform or vessel. Attention is next directed to FIG. 3 which illustrates the preventer stack and casing string in the well bore. The protecter casing is cemented within the well bore 36 which has an enlarged diameter sufliciently deep to accommodate the enlarged protector casing 15. The casing string 12 is also cemented in place at 37 to an adequate depth. The base plate 16 is rested on the floor of the body of water.

At some point in time in the drilling operations conducted through the well casing 12, it becomes necessary to either plug the well prior to abandonment or to remove the preventer stack because production has been obtained. Using the well plug as an example of terminated drilling, known techniques are used to insert a cement plug 38 in the well casing 12. A reversing tool 46 is run into the casing string and positioned adjacent the setting sleeve 22 preliminary to disengaging the preventer stack from the well casing string. The reversing tool 46 is used to disengage the setting sleeve for release of the connectors 11 and 18.

Attention is redirected to FIG. 1 which illustrates the male connecter means 18 as including a plurality of ports 182. The ports 18e are adjacent the shoulder 18a whereby communication from the interior of the casing string 12 is obtained to the annulus thereabout when the setting sleeve 22 is in the partially threaded position of FIG. 1. Conversely, FIG. 2 illustrates complete engagement of the setting sleeve 22 whereby the ports 18e are sealed against communication from the casing string 12. The ports 18e are sealed during the drilling operations until the termination of drilling.

Attention is next directed to FIG. 4 which illustrates the use of the ports 18e after the reversing tool 46 has returned the setting sleeve to the position illustrated in FIG. 1. The downward movement of the setting sleeve relative the connecter means 18 exposes the ports 18e for communication from the casing string into the annulus defined by the protector casing 15. The annulus or chamber, indicated by the numeral 50, is defined by the protector casing 15, the casing member 12a, and the base plate means 16. The base plate means 16 provides a surface which communicates upward force to the preventer stack 20 on accumulation of fluid in the chamber 50 under pressure. The chamber means 50 is particularly defined by the facing walls of the casing members 12a and 15 which extend downwardly to the rubber cup 28 carried on the support ring 29. The rubber cup 28 is constructed and arranged to respond to pressure fluid in the chamber means 50 to slidingly seal against the wall of the preventer casing 15.

A closed fluid system is defined within the casing string for receiving pressure fluid from the drilling platform or vessel. In this regard, attention is directed to the reversing tool 46 which is retained in the well bore after disconnection of the setting sleeve 22 between the male and female connectors 18 and 11, respectively (see FIG. 4). The reversing tool 46 includes a plurality of ports 46a communicating with a tubing string 48 for directing pressure fluid to the well annulus 50. A pair of rams 20b are positioned against the exterior of the tubing string 48 to seal the casing string 12 against flow upwardly in the string. Pressure fluid is delivered through the tubing string 48 as indicated by the arrows 52. The pressure fluid passes through the ports 46a and the reversing tool 46 and is limited in upward or downward escape in the well casing by the 'cement plug 38 and the rams 20 of the preventer stack means. The constraints on flow limit the fluid to passage through the ports 18:: into the annulus means 50.

On delivering an adequate quantity of pressure fluid to the chamber 50, the pressure fluid acts upwardly against the base plate 16 to provide an axial strain upwardly on the casing members 12a and 15. Since the casing member 12a was disengaged from the casing string 12 by setting sleeves 22, the member 12a is free to move upwardly with the base plate 16. Likewise, the protector casing 15 is not joined to the casing string 12 at the flange 13, but merely rests thereon for relatively easy disengagement as shown in FIG. 4. The casing member 15, joined to the base plate 16, imparts a failure circumferentially of the cement at the flange plate 13. A substantial force is required for this failure, although it will also be appreciated that cement is inherently weak in tension and therefore fails without requiring excessive axial strain on the casing 15.

The step of pumping pressure fluid into the tubing string 48 is continued indefinitely until the tubular portion con nected to the preventer stack breaks free of the cement bond with the open hole 36.

As noted above, the step of pumping pressure fluid into the chamber 50 is continued whereby the seal cup 28 slides axially toward the lower end of the protecter casing 15 as the tubular members attached to the preventer stack 20 are expelled from the well bore under pressure. This step is represented in FIG. 4 and FIG. 5 wherein the upward movement frees the seal cup member 28 and the support ring 29 from the lower connecter 11. At this point, with the protector casing 15 substantially expelled from the well bore, and with reduced frictional engagement with the well bore, the preventer stack is easily retrieved by the drilling platform or vessel.

Attention is next directed to FIGS. 6 and 7 which illustrate an alternative method of the present invention. The steps of installing the preventer stack in the well (as illustrated in FIGS. 1 and 2) are omitted, but reference is made to the foregoing description for understanding of the method presently omitted. FIG. 6 is generally similar to FIG. 3 in illustrating a plug in the casing after the well has been abandoned.

The apparatus illustrated in FIG. 6 which bears a similarity to the apparatus shown in FIGS. 1-5, inclusive, bears the identical reference numerals increased by one hundred, and the foregoing description is adequate for FIGS. 6 and 7. In FIG. 6, an inside cutter tool means 146 is run in the casing string 112, and positioned adjacent the setting sleeve 122. Those skilled in the art will appreciate the somewhat schematic representation of the cutter tool 146 which carries the cutting elements 146a against the setting sleeve 122. The setting sleeve 122 is shown in FIG. 6 in the locking position whereby the tubular members 112a and 111 are joined to one another by expansion of the expander ring 123 into the locking position previously illustrated in FIG. 3. The tool means 146 is positioned with the cutting elements immediately adjacent the setting sleeve 122 whereby the cutters 146a are gradually extended as the tool is rotated to form an ever. deepening cut circumferentially interiorally of the setting sleeve 122. When the cutters extend fully through the setting sleeve, the cutting blades are retracted, permitting separation of the male and female connectors 118 and 111, respectively. It should be noted that the cut the setting sleeve not only destroys the structural integrity of the joint and effects a disconnection in the well'j casing string, but the cut also provides access from the interior of the casing string to the annulus for admission of pressure fluid. The chamber means 150 operates in the same manner as the chamber means 50 above noted. At this juncture, reference is made to FIG. 7 which illustrates the next step of the present method.

The cutter tool 146 communicates pressure fluid through the tubing string 148 axially of the well string. Again, sealed means are effected near the well head, and for purposes of illustration, the rams of the preventer stack 120 are extended to seal off the well casing string against upward flow of fluid. The fluid passes through the tubing string 148 and the cutter head 146 into the cut about the circumference of the setting sleeve 122. Reference is made to the separated portions of the setting sleeve attached to the connectors 111 and 118. When the pressure fluid admitted through the tubing string 148 fills the chamber 150 and acts against the base plate means 116, the lifting force on the preventer stack 120 moves it upwardly. Also, the protector casing 115 is lifted upwardly and expelled from the well bore 136. Upward movement of the protector casing imparts circumferential break to the cement about the protector casing 115.

The upwardly movement of the base plate 116 and associated tubular members expands the chamber means 150 by moving the seal cup 128 along the wall of the protector casing 115 to maintain fluid integrity within the chamber means 150. Upward movement of the protector casing 115 is accompanied by upward movement of the casing segment 112a as the preventer stack 120 is retrieved. Hydraulic retrieval of the preventer stack is continued until the preventer stack and tubular segments associated therewith are substantially expelled from the well bore 136 whereupon the friction of the cement jacket against the well bore 136 is substantially reduced. The preventer stack is lifted by conventional apparatus aboard the drilling barge or vessel. Reference is made to FIGS. 4 and 5 associated with the previously described method for illustration of the last steps of the method of the present invention.

Attention is next directed to FIGS. 8 and 9 of the drawings which illustrates an additional alternative in the method of the present invention. Apparatus similar to the apparatus previously noted in FIGS. 1-7, inclusive, bears numerals increased by one hundred. In FIG. 8, the preventor stack means 220 is mounted on the base plate 216, and the casing member 212a is connected to the casing string 212. In addition, the protector casing 215 is placed thereabout and joined to the base plate 216. The casing 215 extends longitudinally of the casing string 212 and rests on a flange plate 213 integrally formed with the casing member 212a.

Of particular interest and contrast in the apparatus shown in FIGS. 8 and 9 is the fact that connecters (see connecters 18 and 11 in FIG. 1) are absent from the embodiment. While no connector means are specified, connection of the casing string to the base plate 216 has the form of integral construction for purposes of the claims. The chamber means 250 is defined by the lower face of the plate 216 and the annulus between concentric tubular members 212a and 215. The lower end of the chamber means 250 is defined by the seal cup 228 which is a circumferential seal carried on the support ring 229. Of particular interest is the variation shown in FIG. 8 wherein the seal support ring 229 is integrally formed with the tubular member 212a comprising a portion of the casing string. While the support ring 229 is illustrated as an integral portion of the tubing string, it will be appreciated that the support ring may be welded or otherwise joined to the casing string. At any event, the support ring 229 carries the seal cup 228 against the interior of the protector casing 215 whereby the chamber means 250 is delimited for receiving pressure fluid therein.

The method of installation in the well bore of the completed assembly shown in FIG. 8 is preferably the same as the foregoing described methods. An inside cutter tool 246 is run on the tubing string 248 for cutting the casing portions 212:: into two segments, an upper segment above the cut at 218 and a lower segment below the cut which is left with the remainder of the casing string. The inside cutter tool 246 is a conventional device known to those skilled in the art. After cutting, the cutter blades 246a are retracted and the casing string is sealed thereabove, perhaps near the well head, preferably by use of the blow out preventer means 220 as illustrated in FIG. 9. At this juncture, the device is ready for admission of pressure fluid through the tubing string 248 and the cutting tool 246.

The pressure fluid fills the casing above the plug 238 and also fills the chamber means 250 previously described. The chamber means is filled to the base plate 216 and an increase in pressure in the chamber means 250 lifts the base plate 216 and the preventor stack 220. The cement jacket joined to the protector casing 215 is fractured near the flange plate 213. As in the previous embodiments noted hereinabove, the seal cup 228 permits expansion of the chamber means 250 but maintains pressure within the chamber means 250 for further expansion. After elongation of the chamber means 250, the seal means 228 is disengaged from the protector casing 215 when the preventor stack 220 has been substantially lifted free of the well bore 236. Then, conventional lifting apparatus on the drilling barge or vessel is used to recover the preventor stack 220.

Attention is next directed to FIGS. 10* and 11 which illustrate further modifications of the method and apparatus of the present invention. In FIG. 10, the apparatus is again shown in the assembled condition in the well bore and reference is made to the foregoing descriptions for an understanding of the method of assembly and placement in the well bore. At the illustrated step of the present method, FIG. 10 shows an abandoned well with a plug 338 in the casing 312. As in the previous descriptions, similar parts have reference numerals similar to previously used reference numerals, increased by one hundred. The casing string is joined or connected to the preventer stack means 320 by the casing member 31211 which eX- tends from the base plate 316 to the casing string 312. The member 312a is welded or otherwise joined to the base plate 316 as will be noted in the drawing. The flange 313 on the casing string 312 supports the protector casing 315 which is Welded thereto in the preferred embodiment. Of particular interest is the fact that the casing 315 is not joined to the base plate 316 as described in previously noted embodiments.

The apparatus shown in FIGS. 10 and 11 also incorporates a seal cup 328 which is carried on a laterally extending support member 329. Of particular interest in this embodiment is the fact that the sealed means 328 is located relatively high adjacent the protector casing string. The seal support 329 is preferably welded or integrally formed with casing member 312a. The high location of the seal means 328 defines a chamber means 350 therebelow extending to the flange plate 313. Again, the chamber means 350 is located in the annulus between the concentric tubular members 312a and 315. The nether side of the support member 329 provides a surface communicating upward lifting force from pressure fluid in the chamber 350 to the preventer stack 320. While the previously described embodiments utilize the base plate to communicate upward lifting to the preventer stack, the present invention utilizes the lower side of the support 329 which communicates the upward force to the tubular member 312a for lifting the preventer stack upwardly.

An inside cutter tool 346 carried on a tubing string 348 is run in the casing string after the cement plug 348 has been placed therein for cutting the well casing as illustrated.

The cutting tool 346 carries conventional cutters 346a extended to form upper and lower portions, it being noted that the upper portion is joined to the preventer stack 320 and the lower portion remains with the casing string 312. Reference is made to FIG. 11 of the drawings which illustrates the use of the tubing string 348 as a conduit for pressure fluid supplied from the drilling barge or vessel. Again, provision is made for some sort of seal means near the well head for maintaining the pressure fluid in the well casing string for admission to the chamber means 350. In any case, the pressure fluid is admitted through the tubing string 348 and is exhausted through the inside cutter tool 346 at the cut 318 which forms a passage means communicating through the wall of the casing string into the chamber means 350. The pressure fluid is admitted thereto and on increase of pressure, acts upwardly against the support member 329 and communicates an upward lifting force to the tubular member 312a which is imparted to the preventer stack carried on the base plate 316. The base plate 316 is lifted free of the protector casing 315 since the protector casing is not joined structurally to the base plate 316 as in the previous embodiments.

FIG. 11 illustrates substantial upward expulsion of the casing portion 312a and the preventer stack 320 as a' means of recovery of the preventer stack. Again, continued addition of pressure fluid to the chamber means 350 is dependent on the seal means 328 engaging the casing 315. The preventer stack means 320 is freed of the well and retrieved to the drilling barge or vessel by conventional lifting apparatus. In contrast to the foregoing methods, it will be noted that the protector casing is left essentially intact and in the well bore joined to the cement jacket. By way of further contrast, it will be noted that the seal cup is recovered by the method presently described whereas the previously described methods left the seal cup and support member in the well bore.

While the foregoing describes the various methods utilizing the apparatus of the present invention, it will be appreciated that the scope of the present invention is defined by the claims appended hereto.

What is claimed is:

1. A method of installing and removing preventer stacks in underwater Wells in which a protector casing is cemented in an open hole and a well casing is placed therein which comprises the steps of:

(a) Threadedly connecting the preventer stack to the well casing by means of a tubular connector;

(b) Forming a pressure fluid tight chamber below the preventer stack;

(c) Said chamber being defined by a surface communicating upward force to the preventer stack on admission of pressure fluid to the chamber;

(d) Disconnecting the well casing from the preventer stack at a point below the preventer stack by unscrewing said tubular connector;

(e) Pumping pressure fluid into the chamber for lifting the preventer stack upwardly on expansion of the chamber; and

(f) Extending the step of pumping pressure fluid into the chamber until the preventer stack and the tubular portion remaining connected thereto break free of the bond with the open hole.

2. The method of claim 1 wherein the step of forming the pressure tight chamber below the preventer stack includes the step of sealing the protector casing to the preventer stack.

3. The method of claim 1 wherein the step of forming the pressure tight chamber below the preventer stack includes the step of forming a seal in the annulus between the well casing and the protector casing.

4. The method of claim 1 wherein the step of pumping pressure fluid includes the steps of providing a path for fluid flow through the well casing into the pressure fluid tight chamber, pumping fluid down the well casing, directing the fluid along the path provided therefor.

5. The invention of claim 1 including the step of using an inside wrench to place a setting sleeve in the well casing to connect the preventer stack to the well casing, and simultaneously closing openings in the well casing communicating with the annulus.

6. The method of claim 1 wherein the step of joining the preventer stack to the well casing is followed by cementing the protector casing in the well bore.

7. An apparatus for installing preventer stacks on under-water wells, comprising:

(a) A tubular connector extending downwardly from the preventer stack, said connector being adapted to be connected to a well casing for use in a casing string;

(b) Chamber means defined by the well casing and exteriorly thereof;

(c) Said chamber means being at least partially defined by a cylindrical surface of predetermined longitudinal extent;

(c Seal means slidably and sealingly engaging said cylindrical surface for confining fluid pressure admitted to said chamber, said surface communicating upward force on the preventer stack moving in response to increased pressure in said chamber means, and said surface movement also expanding said chamber by slidably moving said cylindrical surface relative to said seal means;

(d) Closable passage means for communicating pressure fluid to said chamber means to increase the pressure therein; and

(e) Means for disconnecting the preventer stack from the well casing to free same for movement in response to admission of pressure fluid to said chamber means acting against said surface.

8. An apparatus for installing preventer stacks on underwater wells, comprising:

(a) A tubular connector extending downwardly from the preventer stack, said connector being adapted to be connected to a well casing for use in the casing string;

(b) Chamber means defined by the well casing and exteriorly thereof;

(c) Said chamber means being at least partially defined by a surface communicating an upward force on the preventer stack on increase of pressure in said chamber means;

(d) Closable passage means for communicating pressure fluid to said chamber means to increase the pressure therein;

(e) Means for disconnecting the preventer stack from the well casing to free same for movement in response to admission of pressure fluid to said chamber means acting against said surface;

(f) The nether side of the preventer stack being sealingly joined to a protector casing to at least partially define said chamber means;

(g) A plurality of openings in the well casing; and

(h) Setting sleeve means in the Well casing adapted to be positioned opposite said openings for closing said openings.

9. An apparatus for installing preventer stacks on underwater wells, comprising:

(a) A tubular connector extending downwardly from the preventer stack, said connector being adapted to be connected to a well casing for use in the casing string;

(b) Chamber means defined by the Well casing and exteriorly thereof;

(0) Said chamber means being at least partially defined by a surface communicating an upward force on the preventer stack on increase of pressure in said chamber means;

(d) Closable passage means for communicating pressure fluid to said chamber means to increase the pressure therein;

(e) Means for disconnecting the preventer stack from the well casing to free the same for movement in response to admission of pressure fluid to said chamber acting against said surface;

(f) Said tubular connector being releasably connected to well casing by an axially movable setting sleeve, and the connecting position of said setting sleeve closing said passage means.

10. In underwater wells, the method of removing a preventer stack from a well casing which is cemented in place in a well bore, comprising,

(a) Forming a closed chamber about a portion of the well casing below the preventer stack by means providing a side wall concentric with said casing portion and longitudinally spaced end walls one of which fixedly connects said side wall to said casing portion and the other of which defines a slidable seal between said side wall and said casing portion,

(b) Severing said casing portion at a point between said end walls, and

(0) Introducing pressurized fluid into said chamber to elevate the severed upper section of said casing portion carrying the preventer stack relative to the casing section remaining in the well bore.

References Cited UNITED STATES PATENTS Le Rouax 166--.5 Newsome l66-.5 Smith 166.5 Johnson 166.6 Pittman et al 166.5 X

Marion 166.6

U.S. Cl. X.R.

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