“TRT-S” Mudline Suspension SystemGD-001 Plexus Ocean Systems Ltd “TRT-S” Mudline Suspension System GD-001 Published – 02/08/2001 Plexus Ocean Systems Ltd Page 1 GD001 Plexus Ocean Systems Ltd. “TRT-S” Mudline Suspension Systems GD-001 Contents 1. 2. 3. INTRODUCTION ......................................................................................... 4 SUMMARY OF MAJOR ADVANTAGES .................................................... 5 SYSTEM DESCRIPTION............................................................................. 6 Surface Casing String Installation Methods ..................................................................................... 6 Annulus Washout - Telescopic Running Tool ................................................................................. 8 Hangers Forced Concentric and Parallel ........................................................................................ 10 Hanger Lockdown Facility............................................................................................................. 10 External Test Ports ......................................................................................................................... 10 Split Ring Landing Profile Design ................................................................................................. 11 Temporary Abandonment............................................................................................................... 13 TA Cap Retrieval ........................................................................................................................... 15 Designed for Tieback or Subsea Completion ................................................................................. 16 Mudline Annular Seals................................................................................................................... 17 Additional Hanger Options ............................................................................................................ 17 Dimensionally Designed for 15,000 psi ......................................................................................... 18 4. 5. 6. OPERATIONAL ADVANTAGES............................................................... 19 COST SAVING ANALYSIS ....................................................................... 20 CONTACT DETAILS ................................................................................. 21 PLEXUS OFFICES........................................................................................................................ 21 Plexus Ocean Systems Ltd Page 2 GD001 Page 15 “TRT-S” Mudline System vs Conventional System TA Cap Retrieval. Page 5 “TRT-S” Mudline System Advantages C001 …………………………………………………………………………………………….Page 13 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” with Through Bore TA Cap and Tieback Tools installed. C103…………………………………………………………………………………………….List of Drawings C100……………………………………………………………………………………………. C109……………………………………………………………………………………………. C111…………………………………………………………………………………………….Page 17 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” Casing Programme with Full Bore Annular Seal installed. C008…………………………………………………………………………………………….Page 12 Spilt Cage Design Advantages C107……………………………………………………………………………………………. Page 8 “TRT-S” Mudline System – “TRT” Detail 30” x 20” x 13-3/8” x 9-5/8” Casing Programme showing 20” washout. Running Tools / Tieback Tools shown. C058……………………………………………………………………………………………. C101…………………………………………………………………………………………….Page 18 “TRT-S” Mudline System High Pressure Running Tool configuration.Page 11 Spilt Cage Landing Sequence C112……………………………………………………………………………………………. Page 7 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” with Plug Type TA Cap and Tieback Tools installed.Page 14 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” with Plug type TA Cap. Plexus Ocean Systems Ltd Page 3 GD001 . C110……………………………………………………………………………………………. Page 6 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” Casing Programme with Running Tools installed. generous debris accommodation pockets have been provided to ensure that Mudline Hanger suspension and Tieback Tool engagement can be smoothly effected in an environment that is likely to be contaminated. are forced into a parallel pattern on a common centre line. the Hanger configuration has been tailored to address various requirements for tieback completion or subsea conversion. Dual prealignment surfaces are used to minimise the risk of thread damage during Tieback Tool engagement and to protect the metal to metal seals that are provided for both the Running and Tieback Tools.000 psi use. The "TRT-S" system offers all the features necessary to facilitate easy drilling of a mudline well. To offer continuous control during drilling and completion operations the temporary abandonment system has been so configured that a TA Cap can be installed through the BOP prior to disconnection of the Intermediate Casing Riser and can subsequently be removed following re-installation and testing of the Tieback Wellhead. Plexus Ocean Systems Ltd Page 4 GD001 . By doing so. by the substitution of standard materials with high strength corrosion resistant alloys and the re-location of the washports in the production Casing Hangers. allows the pre-installation of the Surface Casing Starting Head and eliminates the need to use an accurately spaced-out Butt-weld Sub within the Conductor. which can be retracted to expose washports in the Surface Casing Hanger for annulus washout purposes. The Plexus "TRT-S" system has been dimensionally designed and finite element analysed so that the standard system can be upgraded to full 15. tieback operations can occur in a known configuration. the major emphasis on design has been in providing a sound basis for future tieback conversion or subsea conversion. once landed. thereby allowing the Surface Casing String to be hung off in tension.000 psi applications. The "TRT-S" system uses a Telescopic Running Tool. Furthermore. This eliminates the need to rotate the Surface Casing Riser to effect washout.1. The "TRT-S" feature simplifies space-out within the Adjustable Wellhead. Introduction The Plexus "TRT-S" Mudline System represents a second-generation development of mudline suspension technology for use with adjustable Wellhead equipment. The system is specifically designed to facilitate the installation of Mudline Hangers whilst enabling spaceout in the adjustable Surface Wellhead. Our first aim has been to ensure that all the Mudline Hangers. The Telescopic Section of the Telescopic Running Tool is manipulated by the use of a drill-pipe deployed Torque Tool. Wherever possible. However. Plexus engineers for years have worked on the development of specialised mudline suspension equipment for 15. Summary of Major Advantages Running Tools Installed Tieback Tools and TA Cap Installed C100 Plexus Ocean Systems Ltd Page 5 GD001 .2. BUTTWELD SUB IN TENSION Surface Casing String Installation Methods The left-hand side of the drawing C001 shows the Surface Casing Mudline Hanger landed on a Butt-weld Sub. The right-hand side shows the configuration with the Surface Casing String installed in tension. The configuration illustrated on the right-hand side of C001 shows the Surface Casing and Riser Section set in tension at a depth which can be precisely selected and which is measured against the top of the Conductor. ie on the top of the outer conductor. In this situation it is preferable to use a mudline system which enables the location of the Surface Casing Mudline Hanger to be independent of the setting depth of the Conductor. Exploration Drilling In exploration applications. The pertinent features of the system are described in more detail below. the operator may not know the precise distance between the ocean floor and Rotary Kelly Bushing prior to arrival on location. System Description The "TRT-S" Mudline system is offered for the full range of casing programmes generally used in Jack-Up drilling operations. The following considerations apply when selecting the most appropriate installation method. eliminating the need for a Butt-weld Sub. The “TRT-S” Mudline System is designed to allow efficient washout of the Surface Casing Annulus without having to rotate the Riser Section. The system described in this document is configured for a 30" x 20" x 13-3/8" x 9-5/8" casing programme.3. C001 Plexus Ocean Systems Ltd Page 6 GD001 . It is known that under these conditions. the “TRT-S” System enables the Mudline Hangers in each Well to be placed at exactly the same level from RKB. by using identical Surface Riser lengths. or even driven and drilled to locate a Butt-weld Sub at a predetermined depth. or even the loss of the whole Template can occur. If Conductors are drilled and cemented. Plexus again recommend that the Surface Casing be cemented in tension. In template drilling. This not only reduces cost during installation. but also facilitates tieback planning and implementation. The preferred installation method for a Conductor with a fixed landing shoulder is drilling and cementing. as shown in C110. C110 Plexus Ocean Systems Ltd Page 7 GD001 . there is no risk of disturbing neighbouring wells using this installation method. Subsea Conversion For subsea conversion. then the agitation to neighbouring wells during drilling can cause cavities to be formed around and below the Conductors. individual Conductor slippage. As subsea wells tend to be singular. Plexus recommends the use of a specialised Landing Housing to ensure that the distance from the Surface Casing Mudline Hanger to the Mudline Wellhead Conductor Housing is precisely controlled.BUTTWELD SUB IN TENSION Template Drilling In applications where tieback to several wells in a template system is planned. without using a Buttweld Sub. The Plexus “TRT-S” Mudline System allows the Surface Casing Mudline Hanger (the foundation stone for the subsequent tieback operation) to be set at a precise depth. failure to washout. The Telescopic Section is housed between the Running Tool and the Hanger in what constitutes a stiff part of the Surface Casing String. All of the above mentioned problems significantly increase well cost and have the potential to make future tiebacks problematic. the Surface Casing String is cemented in tension and use is made of a cumbersome. Mudline Suspension Systems generally effect annulus washout by rotating the Running Tools to open washports. In such cases.Telescopic Running Tool It is essential that Casing Riser Strings can be easily disconnected at the mudline during well abandonment.Annulus Washout . This procedure requires the casing below the Running Tool to be suspended on a shoulder within the Conductor. The manipulation of the Telescopic Section is thus virtually free of bending loads and requires minimal torque to rotate. annulus washout procedures must operate efficiently. Plexus Ocean Systems Ltd WASHPORTS CLOSED WASHPORTS OPEN Telescopic Running Tool Washout occurs below interface C111 Page 8 GD001 . inefficient and potentially ineffective system of washpipes to clean out the annulus. failure to close washports after circulation or a stuck Running Tool. In circumstances where the Conductor can be accurately located and a Butt-weld Sub is used. Most problems in this area occur with the Surface Casing annulus. The Telescopic Section is therefore not affected by the deflection forces normally present in the Riser. This can result in various problems such as thread or seal damage. can impede rotation of the Running Tools. which can be opened and closed with an internal drillstring deployed Torque Tool. often resulting from Riser misalignment. the bending loads at the Mudline. Such a shoulder cannot always be accurately positioned when Conductors are driven to refusal or even when drilling through a Template. and for this to take place. The "TRT-S" Mudline System uses a Telescopic Running Tool. After washout has been effected. This advantage becomes apparent if unforeseen circumstances cause delay whilst the cement setting time approaches. In order to prevent debris build-up around the Running Tool the washports are located well below the Surface Hanger to Running Tool interface. The left hand rotation necessary to make the telescopic section up acts to tighten the Running Tool thus eliminating any back-off tendency during telescopic section closure). This ensures a clean profile is left for any future tieback or well re-entry operations. In the unlikely event that a Running Tool is disengaged during drilling operations. a metal to metal Interface Seal can be energised. In order to optimise rig operational time the telescopic section can be manipulated with a Torque Tool which is part of the Cement Stinger assembly. This is backed up by dual resilient seals. The Intermediate and Production Mudline Hanger Running Tools utilise a conventional annulus washout system which requires rotation of the Casing Risers. This thread combination ensures that the Running Tool integrity is not compromised during operation of the Telescopic Section. the right hand rotation required to open is thus low torque. (The Telescopic Section is checked on surface prior to being run and made-up hand tight.BUTTWELD SUB IN TENSION Both the Telescopic Section and Running Tool have left-hand threads. This procedure can be implemented literally minutes after the completion of cementing operations. pre-alignment is provided to enable remote re-engagement of the left hand threads whilst protecting the interface seals. C001 Plexus Ocean Systems Ltd Page 9 GD001 . to ensure that during landing both concentricity and parallel positioning is achieved. The Plexus "TRT-S" Mudline System provides such alignment for all hangers. such as HP/HT wells or wells converted to Subsea use. lockdown facilities for the Mudline Hangers can be provided. During onshore make-up of the Hangers and Running Tools these ports are used to eliminate the need for expensive and time consuming body tests. C001 Plexus Ocean Systems Ltd Page 10 GD001 . External Test Ports To facilitate hanger interface seal testing. BUTTWELD SUB IN TENSION Hanger Lockdown Facility For specific applications. The "TRT-S" Split Ring Hanger utilises a setting mechanism which prevents early release of the Split Ring. tieback procedures have to be effected. Seal integrity can be verified prior to running an assembly. all Running Tool seals are equipped with external Test Ports. provisions have been made in the design of both shoulder type and split ring Hangers. This is particularly appropriate for wells where thermal expansion is a problem. To control the position of each Hanger.Hangers Forced Concentric and Parallel When utilising a Mudline Well for production applications. representing a considerable cost saving. whilst also acting as a centraliser. The feasibility of such procedures is greatly facilitated if the Mudline Hangers are arranged in a predictable configuration. Split Ring Landing Profile Design The Landing Profile for the Split Ring Hanger is designed with debris accommodation pockets in which contamination is dispersed during expansion of the Split Ring. as utilised in some systems. The Plexus Split Ring design also features dual concentricity – the Production Hanger is forced concentric by the Split Ring in two places. This eliminates the need for a costly additional run with a landing profile clean out tool. this ensures that the hanger is parallel to the Intermediate Casing Hanger. As well as ensuring concentricity. Dual Concentricity Split Cage being run through 13-3/8" Hanger Mating profile located Hanger landed and set in position C058 Plexus Ocean Systems Ltd Page 11 GD001 . facilitating tieback and allowing the use of an annular seal. Plexus Split Cage Competitor Split Cage SURFACE WELLHEAD RISER Bending stiffness is equal above and below compression point Compression point is below centre of bending stiffness Split Cage collapses evenly. to ensure that landing shoulders are protected from damage during installation and to prevent premature setting.One further advantage of the Split Ring is that it has been designed to collapse evenly. Other systems collapse such that the landing shoulders are the outermost part of the component as it is forced to collapse. This leaves teeth exposed and subject to hang-up or damage Plexus Ocean Systems Ltd Page 12 GD001 . Drawing C112 below demonstrates the advantage of the Plexus design over other systems. ensuring landing shoulders are protected C112 Split Cage collapses further at the bottom. RUNNING TOOLS TIEBACK TOOLS Through Bore TA Cap C107 Plexus Ocean Systems Ltd Page 13 GD001 . The seal utilises an expandable resilient element that is activated by wedge action. This leaves Mudline Hanger Profiles. The Through Bore TA Cap has been designed with full consideration of future tieback or well re-entry operations.Temporary Abandonment When a Rig leaves its location the Casing Risers are disconnected. The unit is engaged within the Production Casing Hanger with a stab type Threaded Ring and locks itself into the Intermediate Mudline Hanger with a Lock Sleeve activated by the downward motion of the TA Cap relative to the Production Casing Hanger. exposed to the environment. A "Jay"-Type Running Tool is designed to allow for testing of the Annular Seal. which is installed in the Production Casing Hanger profile. The unit seals the Production Casing annulus only. This locking action secures the Mudline Hangers in position and eliminates Casing rise. Another major advantage of the Through Bore TA Cap is that an inner tool string can be used for weight or guidance purposes. under the BOP's. Conventional systems use a number of plug type Temporary Abandonment Caps to plug the Well and to protect the Tieback Profiles. designed to accept Production Equipment. Operators with Tieback experience will know how essential this feature is during the re-establishment of outer Tieback Strings. The Plexus "TRT-S" system offers a single annular Through Bore Temporary Abandonment Cap. The design allows the facility to first tieback the Intermediate Casing Riser prior to removing the Cap through the Tieback Wellhead after BOP nipple up has occurred. RUNNING TOOLS TIEBACK TOOLS Plug Type TA Cap C103 Plexus Ocean Systems Ltd Page 14 GD001 . the "Plug Type Abandonment Cap" is designed to lock the Mudline Hangers in position thereby preventing casing rise. The "TRT-S" Abandonment Cap is subsequently retrieved through the Tieback Wellhead. The Cap allows tieback of the Intermediate Casing riser prior to retrieval and it is also possible to separately establish pressure in either the Production Casing Bore or the Production Casing Annulus prior to the cap being removed. This procedure can be implemented under controlled conditions should pressure be found to be present under the Cap. Finally.A plug type TA cap is available for operations where it is not feasible to plug the well by alternative methods. The "TRT-S" Abandonment Cap has been positioned so as to allow the settlement of debris on top of the Cap without interfering with the Intermediate Casing Riser Tieback procedure. similar to the "Through Bore TA Cap". The Plexus “Plug Type Abandonment” cap seals the Production Casing Bore as well as the Production Casing Annulus. In this mode the "TRT-S" Abandonment Cap can be effectively used as a tieback seal test tool for the Intermediate Casing Riser. which allows pressure monitoring or relief in both the annulus and the bore independently. During years of experience with tieback technology the Plexus team has learnt to appreciate the value of debris pockets. The "Plug Type Abandonment Cap" has a pressure balanced relief valve. which could make retrieval impossible Eg: 5000 psi results in 200 kips contact force between Caps 2 Feet 1 Foot 11" 10" 9" 8" 7" 6" 5" 4" 3" 2" DATUM 1" 0 1" 2" 3" 4" 5" 6" 7" 8" 9" 10" 11" 1 Foot 2 Feet 3 Feet C101 Plexus Ocean Systems Ltd Page 15 GD001 . In the “TRT-S” system. so the well could be lost. Pressure has built up in the bore. which could occur if the TA Cap is not locked down.TA Cap Retrieval As mentioned previously. can be bled off in a controlled manner through the pressure balanced release valve. in either the bore or annulus. In the conventional system on the right. Conventional systems do not offer this. is shown. Plexus "TRT-S" System No movement as Hanger is locked down by TA Cap. the lower cap will move upwards with casing rise. Pressure can be released through pressure balanced valve before Cap is retrieved Other Systems Pressure in the bore forces lower Cap against upper Cap. and any pressure build up. One potentially disastrous scenario. no hanger movement can occur. as is shown in drawing C101 below. This prevents movement of the Hangers if pressure builds up below the Cap. pressing on the upper cap with significant force. The resultant load on the threads of the upper cap make disengagement difficult if not impossible. both the Through Bore and Plug Type TA Caps have the facility to lock down the Production Hanger as a standard feature. the Plexus "TRT-S" Mudline system offers a number of redundant seal areas in the Tieback Profiles. which needs minimum rotation to effect engagement. BUTTWELD SUB IN TENSION REDUNDANT SEAL AREA C110 Plexus Ocean Systems Ltd Page 16 GD001 . An FEA study can be made available to confirm suitability under specific fatigue loading conditions. The inner Casing Risers are connected with Stab-type Tieback Tools which use a Threaded Split Ring mechanism.Designed for Tieback or Subsea Completion The Plexus "TRT-S" Mudline system uses a Riser Tieback method. To prevent cross threading during remote engagement. To facilitate a successful tieback. For Subsea Wellhead conversions the "TRT-S" Mudline system can be specified with lockdown devices for each Mudline Hanger. In the case of the outer Tieback Riser. the "TRT-S" Mudline system offers a fatigue resistant tapered threaded connection. each tieback profile is provided with dual pre-alignment surfaces. which can be utilised should the primary seal areas be inadvertently damaged. In order to accurately control the recommended setting torque for each of the tieback connections internal torque profiles are provided for each tieback tool to allow use of a drill string deployed Torque Tool. thus protecting the thread profiles and preventing any damage occurring to the metal to metal Tieback Seals. A hydraulically tensioned Tieback Mechanism ensures that the Subsea Crossover Hangers are installed with positive downward load thus enabling the use of metal to metal Annular Seals. which engages with 1-1/4 turns of right hand rotation. where optimum bending and tensile capacities are critical. which can be installed directly below the Mudline Production Casing Hanger or at any other convenient location specified. The annular seal is similar in design to the TA Caps. as shown in drawing C109. C109 Plexus Ocean Systems Ltd Page 17 GD001 . the "TRT-S" Mudline system can be supplied with an Annular Seal which bridges the Production Casing and Intermediate String annulus.Mudline Annular Seals For casing programmes where Surface Casing is omitted and the Intermediate Casing Riser is designed to contain full well pressure. in that it provides single trip installation as well as positive lock-down for the Production Hanger. Full Bore Annular Seal Additional Hanger Options To enable the operator to install an extra Casing String the Plexus "TRT-S" Mudline system offers the option of an additional Mudline Hanger Assembly. which sets a metal to metal interference seal. The Running and Tieback Tools are designed with a tapered right hand thread. increasing hoop force resistance. if required. the seal design utilised within the Plexus mudline systems can be classified as a genuine metal to metal 15.000 psi service. and by relocating the washports to the Production Casing Hanger. Standard Configuration Washports in Running Tool High Pressure Configuration Washports in Hanger to increase pressure rating C008 Plexus Ocean Systems Ltd Page 18 GD001 .Dimensionally Designed for 15.000 psi Over many years Plexus have worked on the development of Mudline Systems for high temperature and high pressure applications. The Plexus Ocean Systems "TRT-S" Mudline system has been dimensionally configured and finite element analysed to enable the option of upgrading the system to full 15.000 psi seal. This is achieved by substituting standard materials with high strength corrosion resistant alloys such as Inconel. In addition. Dual concentricity places all Hangers on identical centre line facilitating tie-back. Split Cage design prevents accidental damage during installation. Surface Wellhead Starter Head is pre-installed eliminating field welding. Split Cage run without the need to clean the receiving profile. Single trip stab-type dual TA Cap. ie set at surface in tension. Surface Casing Mudline Hanger washports are located below the Running Tool interface. Plexus Ocean Systems Ltd Page 19 GD001 . Typical Systems do not offer many of the above features. Running Tool to Hanger interface seal can be tested externally just prior to running through rotary table . Separate Running (LH) and Tieback (RH) Threads. some of which are critical to safe well operations.Onshore body tests for Hanger are eliminated saving cost. Isolated Tie-back Seal test capability. Seal area is provided for production bore Annular Seal. Monitoring facility of production bore and annulus through TA cap valves.4. Lock-down profile is provided for production Mudline Hanger. Dual stab-type TA Cap set prior to removal of BOP. Operational Advantages • • • • • • • • • • • • • • • • • • • Surface Casing Riser annulus is washed without riser rotation. Washout procedure with Circulating Swage reduces time period between completion of cementing and starting of washout from hours to minutes. Surface Casing does not require landing ring. Pressure balanced cementing procedure eliminates risk of Casing collapse. Hanger/Running Tool assembly interface connections remain unused and protected prior to installation (no onshore testing with end caps is necessary). Dual TA Cap retrieved after installation of Tie-back Wellhead under controlled conditions. Time related: • Surface Starting Head is preinstalled • Surface casing riser annulus washed without riser rotation • Split Cage landed without profile cleanout run • Single trip T/A and lock-down cap Total Hours Saved Total Time Related Savings (@ £ 80.667 Potential additional savings: In addition to the above savings.000 £ 41. These features are difficult to quantify. • Through Bore TA Cap enables the use of a drill pipe guide string to aid difficult tieback. but can be seen as ‘insurance’ against potential problems which may greatly impact the final cost of well completion.667 £ 2.000 per day rig rate) Other savings: • Welding Starter Head (Personnel and Equipment) • External test ports in Running Tools eliminate need to perform onshore body tests with end caps Total Other Savings: Grand Total Savings per Well: 4 hrs 3 hrs 2 hrs 2 hrs 11 hrs £ 36. the Plexus “TRT-S” Mudline System offers features which facilitate subsequent tieback operations or sub-sea conversion procedures: • Dual alignment of Hangers ensures a known configuration.000 £ 5.000 £ 3. • Pre-alignment profiles prevent cross-threading. Cost Saving Analysis This analysis shows cost savings as a result of using Plexus “TRT-S” Mudline Suspension System over conventional mudline equipment during the drilling phase.5. Plexus Ocean Systems Ltd Page 20 GD001 . Ashley Base Pitmedden Road Dyce Aberdeen AB21 0DP Tel: +44 (1224) 774222 Fax: +44 (1224) 774333 E-mail: [email protected] Other Offices: Plexus Ocean Systems Ltd Plexus House 1 Cromwell Place London SW7 2JE Tel: +44 (207) 589 8555 Fax: +44 (207) 589 8554 E-mail: [email protected]. Contact Details PLEXUS OFFICES Plexus Ocean Systems Ltd Unit 1.com Plexus Ocean Systems Inc Suite 120 1224 North Post Oak Road Houston Texas 77055 Tel: +1 (713) 686 5267 Fax: +1 (713) 686 0275 E-mail: [email protected] Plexus Ocean Systems Ltd Page 21 GD001 .