US3513911A - Offshore well workover method - Google Patents

Description

May 26, 1970 w. H. PETERSEN 3,513,911

OFFSHORE WELL WORKOVER METHOD Filed May 24. 1968 2 Sheets-Sheet 1 INVENTOR:

WILLIAM H. PETERSEN aYcfl yggr HIS ATE QRNEY May 26, 1970 w. H. PETERSEN 5 OFFSHORE WELL WORKOVER METHOD Filed May 24, 1968 2 Sheets-Sheet 2 INVENTOR= WILLIAM H. PETERSEN HIS ATTORNEY United States Patent 3,513,911 OFFSHORE WELL WORKOVER METHOD William H. Petersen, Houston, Tex., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed May 24, 1968, Ser. No. 731,993 Int. Cl. E21b 7/12; E21c 19/00 US. Cl. 166-.6 2 Claims ABSTRACT OF THE DISCLOSURE A method of lowering apparatus to an underwater wellhead assembly from a floating vessel, attaching the apparatus to the wellhead assembly, establishing guidelines between the vessel and a structure on the ocean floor, and retrieving at least a portion of the attached wellhead assembly to the vessel along the guidelines by said apparatus.

This invention relates to a method of carrying out operations with respect to underwater wells at deep water locations from a floating vessel.

More particularly, the present invention relates to a method of establishing contact between an apparatus lowerable from a floating vessel and an underwater wellhead structure whereby guideline means are established between the vessel and the structure and at least a portion of a wellhead assembly may be retrieved along said guidelines. The aforesaid operations may be carried out remotely from said vessel.

During recent years, the continued search for oil has resulted in developing methods and apparatus for drilling underwater wells at locations where the water may range from 100 to 1,500 feet or more in depth. In these locations, it has become the widespread practice to position a wellhead at a considerable distance below the surface of the water, preferably on the ocean floor, so that it is not a hazard to navigation of ships in the area.

One method of drilling and completing an underwater well on the ocean floor is described in US. Pat. No. 3,256,937, issued to J. A. Haeber et al. on June 21, 1966. In the method described in that patent, a wellhead structure, including a wellhead assembly, is positioned on an underwater wellhead and a series of guidelines extend from the wellhead structure to a drilling barge or other drilling vessel floating on the surface of the water. Through the use of the guidelines various pieces of equipment are raised and lowered between the wellhead structure and the vessel. After well drilling operations have been completed, the guide cables are left permanently attached to the wellhead structure at their lower ends and are secured, preferably to a buoy, at their upper ends, with the buoy floating on the surface of the water, whereby they may be used subsequently to reestablish contact with the structure. Alternatively, the cables are dropped to the ocean floor from which they are recovered later by means of grappling hooks or other suitable means. Since cables lying on the ocean floor tend to become entangled as well as constituting a hazard to sea traflic, it is desired that these guide cables be removed when drilling operations have been completed.

It is, of course, necessary to periodically perform workover or maintenance operations with respect to an underwater well and associated wellhead assembly. Accordingly, special wellhead assemblies have been designed and constructed that can be readily removed from the underwater wellhead and raised to the surface. One underwater wellhead structure of this type is shown and described in US Pat. No. 3,064,735, issued Nov. 20, 1962, to R. J. Bauer et al. To insure the safe and rapid transport of the wellhead assembly to the surface, as

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well as to provide means whereby it may be returned to the underwater wellhead after the desired operations have been performed, some form of guide means is preferably disposed between the vessel and the underwater wellhead. As previously stated, however, the common practice is to remove guide cables or guidelines from the underwater wellhead structure when drilling operations have been completed.

SUMMARY OF THE INVENTION It is therefore a primary object of this invention to provide a method whereby guideline means are remotely established between an underwater wellhead structure and a floating vessel and at least a portion of a wellhead assembly is removed to the vessel along the guidelines.

A still further object of the present invention is to provide a method whereby retrieval apparatus and guide carrying means are substantially simultaneously lowered from a floating vessel to an underwater wellhead structure whereby the retrieval apparatus is attached to a wellhead assembly, guidelines are established between the vessel and the structure, and at least a portion of the assembly is pulled to the vessel by the retrieval apparatus.

The above objects have been attained in the present invention by providing a method of retrieving at least a portion of an underwater production wellhead assembly, comprising part of an underwater structure, to the surface of a body of water wherein retrieval apparatus and guide-carrying means are lowered from a vessel and positioned on a previously located assembly. The retrieval apparatus is then connected to the assembly and guide means are lowered from the guide carrying means and connected to the remainder of the structure. The portion of the wellhead assembly to be retrieved is then disconnected from the remainder of the structure and pulled to the water surface along the guide means.

DESCRIPTION OF THE DRAWING These and other objects of the invention will be understood from the following description taken with reference to the drawing wherein:

FIG. 1 is a diagrammatic, frontal view taken on longitudinal projection illustrating a vessel floating on a body of water with retrieval apparatus and guide carrying means depending therefrom and positioned over an underwater wellhead structure, including a wellhead assembly;

FIG. 2 is a diagrammatic, side view taken on longitudinal projection of the retrieval apparatus, guide carrying means, and underwater wellhead structure, in the relative positions illustrated in FIG. 1;

FIGS. 3 and 4 are diagrammatic, frontal views taken on longitudinal projection showing the relative positions of the retrieval apparatus, guide carrying means and underwater wellhead structure during various stages in the operation thereof while carrying out the steps of the method according to the present invention; and

FIG. 5 is a diagrammatic, side view taken on longitudinal projection showing thte wellhead assembly portion of the wellhead structure being pulled to the surface of the body of water by the retrieval apparatus along guidelines attached to the wellhead structure.

Referring to FIG. 1 of the drawing, a workover vessel, barge, or platform 11, of any suitable floatable type, is illustrated as floating on the surface of a body of water 12 while being substantially fixedly positioned over a preselected well location by suitable vessel positioning means well known to the art, or by being anchored to the sea bed 13 by anchor lines 14 and 15 running to anchors (not shown). Equipment of this type may be used when carrying out underwater well workover operations in water depths varying from about to 1500 feet or more. The

workover vessel 11 is equipped with a suitable derrick 16 as well as other auxiliary equipment needed for operations of this type. The derrick 16 is positioned over a slot or well 17 which extends vertically through the vessel in a conventional manner. When carrying out the various steps of the method according to the present invention, the slot 17 of the vessel may be either centrally located or extend in from one edge. However, operations may be carried out over the side of the barge or vessel without the use of a slot. Additionally, it is to be understood that the method of the present invention may be used also when performing operations with respect to a well from any suitable operational base positioned above the surface of the water, such as, for example, from a barge having legs extending to the ocean floor or from a platform permanently positioned on the ocean floor.

An underwater wellhead structure 18 is located on the sea bed 13 below vessel 11. It is to be assumed that the vessel has been positioned as illustrated through the use of conventional navigational aids and anchored. The wellhead structure 18 includes a base member 19 having a pair of upstanding guide posts 20 and 21 fixedly mounted thereon. A well casing 22, which extends into the sea bed 13 as shown, and is preferably fixedly secured therein as by means of cement 23, passes through base member 19 and terminates at its upper end with wellhead member 24. A production wellhead assembly 25 is mounted on wellhead member 24. Although the method according to the present invention may be carried out with a wellhead assembly construction of any suitable type, for ease of explanation and convenience, it will be assumed that wellhead assembly 25 will be of the type disclosed in afore mentioned US. Pat. No. 3,064,735. As with the wellhead assembly disclosed therein, assembly 25 is of a Y-branched construction and includes a central body having fluid flow handling conduits 26 and 27 extending therefrom which communicate, respectively, with production conduits 28 and 29 extending into the well within casing 22. The outer ends of conduits 26 and 27 terminate at connectors 30 and 31 as shown. The connectors may be of any suitable remotely-detachable type, one example of which is disclosed in US. Pat. -No. 3,052,299, issued Sept. 4, 1962, to Geer et al. The connectors 30 and 31 establish fluid flow communication between conduits 26 and 27 and production flow lines, such as flow line 32 (FIG. 2), which are positioned on sea bed 13 and lead to a suitable storage facility (not shown) in the usual manner.

Depending from vessel 11 by means of pipe string 33 is an arrangement comprising a retrieval apparatus 34 and guide carrying means 35. The particular arrangement shown is disclosed in copending US. application Ser. No. 731,382, filed May 23, 1968, and is set forth here for illustration purposes only. It is to be understood that other suitable arrangements may be utilized in carrying out the steps according to the present invention. As is set forth in more detail in the aforementioned U.S. application Ser. No. 731,382, retrieval apparatus 34 includes lock means (not shown) operative upon positioning of the retrieval apparatus upon production wellhead assembly 25 to lock the retrieval apparatus to the wellhead assembly. As is also shown in greater detail in the last-mentioned US. application, guide carrying means 35 includes a pair of cylindrical housing members 36 and 37 which are frame-mounted on retrieval apparatus 34. Slidably mounted in housing members 36 and 37 are elongated connector elements 38 and 39, respectively, which terminate at their lower ends in cone-shaped members 40 and 41. Suitable latching means, such as latching member 4111 (FIG. are disposed in cone-shaped members 40 and 41 and are connected to guidelines 42 and 43 (FIG. 1) which extend to vessel -11 in the manner illustrated. Guidelines 42 and 43, respectively, are operatively associated with constant tension hoists 44 and 45 disposed on vessel 11. As is shown in aforementioned US. application, Ser. No. 731,382, the constant tension applied to guidelines 42 and 4 43 serves to retain cone-shaped members 40 and 41 against the lower ends of housing members 36 and 37 and the latching means seated within the cone-shaped members The method according to the present invention will now be described. Again, although such method will be described with particular reference to the apparatus shown in the drawings, the method steps may be carried out through the use of other desired means consistent with the requirements of practice or the exigencies of given conditions.

After the retrieval apparatus and guide-carrying means have been assembled in the manner shown in FIG. 1, the assembled unit is lowered from vessel 11 by lengthening pipe string 33 in the customary manner, i.e., through the addition of individual pipe sections to the string. Throughout this lowering operation, constant tension is maintained on guidelines 42 and 43 by hoists 44 and 45, thereby retaining the latching members within coneshaped members 40 and 41 and keeping the cone-shaped members in contact with the lowermost ends of housing members 36 and 37. The arrangement comprising the retrieval apparatus and the guide carrying means is lowered until it has been determined that the lowermost portion thereof is positioned a distance from the sea bed 13 somewhat greater than the height of the production wellhead assembly 18, as shown in FIGS. 1 and 2. At this point, wellhead assembly locating means, such as sonar unit 46 and/or television camera 47, are actuated and monitored from the vessel 11 in the customary manner. Using this information, the operator then positions the retrieval apparatus directly over the wellhead assembly in any known manner, such as by manipulating the pipe string.

Still further lowering of the retrieval apparatus and guide carrying means then brings the retrieval apparatus into engagement with the underwater wellhead assembly as shown in FIG. 3. Outwardly flanged member 48 is preferably provided on the lower end of the retrieval apparatus to assist in properly axially aligning retrieval apparatus 34 over wellhead assembly 18 as it is lowered thereupon. Although not illustrated herein, cooperating orienting means will preferably be provided on said retrieval apparatus and said wellhead assembly to also rotatably align the retrieval apparatus to a predetermined position with respect to the assembly as the retrieval apparatus is lowered. Suitably orienting means for this purpose are disclosed in US. application, Ser. No. 731,382, wherein a pin on the retrieval apparatus operates with a slot on the wellhead assembly to effect rotatable movement. When the lowering operation has been completed and the retrieval apparatus and the wellhead assembly are located relative to each other as shown in FIG. 3, the lock means (not shown) associated with the retrieval apparatus is actuated to lockingly engage the retrieval apparatus to the wellhead assembly.

It should be noted that when the retrieval apparatus has been positioned, oriented, and locked, as previously described, with respect to the wellhead assembly, housing members 36 and 37 of the guide carrying means are axially positioned over upstanding guideposts 20 and 21. By releasing the tension on guidelines 42 and 43, cone-shaped members 40 and 41 with their respective latching members are dropped over guideposts 20' and 21 as shown in FIG. 4 under the influence of gravity. The latching members are then automatically latched by means of any suitable mechanism to the guideposts. At this point, the required remote disconnect operations are made with respect to the wellhead assembly to close down the well and enable at least a portion of the Wellhead assembly to be raised to the surface of the water. The operation of the various valves, latches, etc. involved when performing such disconnects may be effected by use of any known expedient, such as hydraulic or electric conduits extending from vessel 11.

FIG. 5 illustrates the operation of raising at least a portion of the wellhead assembly to the surface after required disconnects have been made as discussed in the preceding paragraph. In this instance, the entire assembly 18 is being pulled to vessel 11 from wellhead member 24 by means of pipe string 33 and retrieval apparatus 34. It should be noted that the flow handling conduits, such as conduit 27, have been disconnected from their respective flow lines, such as line 32. The latching members, such as latching member 41a, remain attached to their respective guideposts as the wellhead assembly portion is pulled upwardly with guidelines 42 and 43 cooperating with housing members 36 and 37 to guide the upward course of movement of the retrieval apparatus 34, guide carrying means 35, and said wellhead assembly portion. After the wellhead assembly portion has been repaired or wholly or partially replaced, the guidelines 42 and 43 may be subsequently used to guide it into position on the wellhead as the lowering thereof is etfected, such as by lowering it by means of a pipe string.

I claim as my invention:

1. A method of retrieving to the surface of a body of water at least a portion of an underwater production wellhead assembly, said assembly comprising part of an underwater wellhead structure, said method comprising:

assembling together retrieval apparatus and guide-carrying means;

simultaneously lowering the assembled retrieval apparatus and guide-carrying means from a vessel floating on the surface of a body of water while maintaining said assembled retrieval apparatus and guide-carrying means operatively disassociated from said underwater wellhead assembly;

locating said underwater wellhead assembly;

positioning said retrieval apparatus in engagement with said underwater wellhead assembly;

orienting said retrieval apparatus to a predetermined rotatable position with respect to said Wellhead assembly;

connecting said retrieval apparatus to said wellhead assembly; lowering guide means from said guide carrying means; connecting said guide means to the remainder of said underwater wellhead structure; I disconnecting at least a portion of said wellhead assembly from said remainder of said structure with said portion attached to said retrieval apparatus;

raising said retrieval apparatus and the attached portion .of said wellhead assembly to the floating vessel; and

guiding the retrieval apparatus and the attached portion of the wellhead assembly along said guide means as the retrieval apparatus and the attached portion of the wellhead assembly are being raised to the vessel.

2. The method of claim 1 wherein the connecting of said guide means to the remainder of said structure is carried out by dropping the guide means from said guide carrying means and permitting the guide means to fall under the influence of gravity until operative engagement is made between the guide means and the remainder of the structure.

References Cited UNITED STATES PATENTS 3,021,909 2/196-2 Postlewaite 7 3,050,140 8/1962 Hayes 175-7 3,064,735 11/ 196-2 Bauer et a1. 166-.6 3,166,123 1/ 1965 Watkins 166-.6 3,23 6,302 2/ 1966 Postlewaite 1757 X NILE C. BYERS, Sn, Primary Examiner R. E. FAVREAU, Assistant Examiner US. Cl. X.R. 1757

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